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Discussion Starter · #61 ·
Scanning back through this thread i didn’t see mention of an aftermarket tune. Is this engine bone stock?
If you are taking it to GM I would ask if they can test the harness for proper electrical levels everywhere.

If you haven’t already also load test the battery.

just guessing here but it does seem to be leaning into an electrical issue . That could be a failing ECM, down the wiring harness all the way to the connectors and fuse box. This would include checking the coils as well as the harness running to the fuel injectors. Checking the vehicles grounds (including the stereo and especially if you have an aftermarket one as I have read of wacky behavior around a poorly wired head unit)

all of the above seems unlikely however it has to be something and starting with the ECM connectors and working your way down the line seems logical.

not sure if there is a way to test the ECM itself but you can sure check the connectors for corrosion and such.
I am sure others more experienced may be able to pint you in a better direction…
yes, bone stock. He did check all the grounds and found zero corrosion. Battery was tested but I don’t know if it was load tested. I’ll see what happens after the carbon cleaning next week. I’m hoping that’s the issue. I’m shocked at 50k it could be that but we’ve seen caked up valves on less miles. He did say it doesn’t take a lot with these cars even being built 15 years ago they can be very finicky.
your harness is not damaged. The CEL will turn off after a couple cycles of the key if the problem hasn't continued. it is likely that it is a coincidence and nothing more because you would not have had the CEL go out from a change you just made. carbon buildup on the valves does not mean that it wold cause a consistent problem. temperature, humidity and how you are driving the vehicle can be the kid poking the stick into the fire ant nest. easiest way to know if that is the problem is to use an endoscope so you can view the backs of the valves with out having to take a whole mess of things apart.
thanks as well. I’m hoping this is the case. You are the one who posted the link to the endoscope you bought correct and it hooks up to a smart phone? If so, would you mind telling me which one it was? I can remember the thread I saw it in. I’d like to have one.

Another question, they are using some potent chemical. They pour a few ounces in each cylinder and let that soak a couple hours along with spraying into the the throttle body while running obviously. Oil must be changed afterwards. Should I be worried about scoring the cylinders when they start it up? This stuff will dissolve any oil on there. I thought about seeing if they can drop some oil in there before starting up but that’s not going to cost the walls very well.
 

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there is no chemical that is going to be the magic cure. It may make the misfire go away because the chemical will remove the softer carbon. but the stuff that is baked on over many years is only going to come off by being blasted by dry ice or walnut shells.

I wanna say DPS tech or something of that sort. They make many cameras so so let me look back in my Amazon purchase history and locate the one I bought. It work over WiFi and it has a battery in it so you don't have any cords. It does have a 16' whip for the camera so it is not limited to only automotive use.
 
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Discussion Starter · #63 ·
there is no chemical that is going to be the magic cure. It may make the misfire go away because the chemical will remove the softer carbon. but the stuff that is baked on over many years is only going to come off by being blasted by dry ice or walnut shells.

I wanna say DPS tech or something of that sort. They make many cameras so so let me look back in my Amazon purchase history and locate the one I bought. It work over WiFi and it has a battery in it so you don't have any cords. It does have a 16' whip for the camera so it is not limited to only automotive use.
Thanks so much. I’ll try and look again on here for that thread. I’ll look at Amazon too. I appreciate the info. Have ever walnut blasted the valves on your car or any car? Also, I’m thinking of getting a catch can. I’ve heard on here mixed reviews about its effectiveness on our cars. Would one benefit our car to further prevent this carbon buildup? I believe you said you have one and just wonder if you are catching any oily residue in yours? Thanks
 

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The mixed reviews is because of how it is put on and where it is mounted. There is a very specific way to do it that will allow it to work the best. Most people believe the oil issue stems from the line that attaches to the turbo and that is not the case. most of the oil comes out of the vent line attached to the intake pipe. This is because the "blow off valve" for the turbo blows the air back into the intake pipe directly across from where the line for the PCV attaches. The amount of excess air and pressure that gets blown back ends up going into the valve cover because it is under a vacuum so air ends up moving backwards through the PCV system. Th line that is attached to the turbo is baffled inside the valve cover, while the baffles are not perfect they keep most of the oil vapor from going down the line and into the turbo. The system was not designed to have air moving in reverse through the system. GM knew about the problem that is why there is a check valve on the vent line. The valve is a band-aide and just like all band-aides it will eventually fall off (stop doing it's job).

It is better to put 2 catch cans but that can get a bit spendy if doing a really good job running the lines and using AN fittings. I spent about 500.00 on my dual catch can setup. It looks really good. I have not had the opportunity to really drive the vehicle since I installed it but there was a little bit in the cans after a couple of drives. So it does work.

You cannot have any low spots or "dips" in the lines The lines MUST be pitched otherwise any oil or moisture that condenses in the line is going to fill the line up and there may not be enough of a vacuum to move that much oil. This is one of the failures in a lot of installations. The other thing is you get what you pay for. a 20 or 30 dollar catch can is more then likely not going to work as well as a 100+ dollar catch can. You have to do your research on this one. The other thing is I believe that people may ot be connecting them correctly. the "IN" port on the car MUST always be attached to a line that goes to the valve cover. YOu also want to make sure the catch can does not have a check valve in it. some of them do and they are built in. We really don't care which way the air flows if using a 2 can system so let it do whatever it is it wants to do and all we need to worry about is cleaning oil out before the vapors get to the intake.
 
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Here is the camera. It's 45.00, 5.0 megapixel. I don't believe the 5.0 megapixel part but it does give a good quality image for how much it costs.

 
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Discussion Starter · #66 ·
The mixed reviews is because of how it is put on and where it is mounted. There is a very specific way to do it that will allow it to work the best. Most people believe the oil issue stems from the line that attaches to the turbo and that is not the case. most of the oil comes out of the vent line attached to the intake pipe. This is because the "blow off valve" for the turbo blows the air back into the intake pipe directly across from where the line for the PCV attaches. The amount of excess air and pressure that gets blown back ends up going into the valve cover because it is under a vacuum so air ends up moving backwards through the PCV system. Th line that is attached to the turbo is baffled inside the valve cover, while the baffles are not perfect they keep most of the oil vapor from going down the line and into the turbo. The system was not designed to have air moving in reverse through the system. GM knew about the problem that is why there is a check valve on the vent line. The valve is a band-aide and just like all band-aides it will eventually fall off (stop doing it's job).

It is better to put 2 catch cans but that can get a bit spendy if doing a really good job running the lines and using AN fittings. I spent about 500.00 on my dual catch can setup. It looks really good. I have not had the opportunity to really drive the vehicle since I installed it but there was a little bit in the cans after a couple of drives. So it does work.

You cannot have any low spots or "dips" in the lines The lines MUST be pitched otherwise any oil or moisture that condenses in the line is going to fill the line up and there may not be enough of a vacuum to move that much oil. This is one of the failures in a lot of installations. The other thing is you get what you pay for. a 20 or 30 dollar catch can is more then likely not going to work as well as a 100+ dollar catch can. You have to do your research on this one. The other thing is I believe that people may ot be connecting them correctly. the "IN" port on the car MUST always be attached to a line that goes to the valve cover. YOu also want to make sure the catch can does not have a check valve in it. some of them do and they are built in. We really don't care which way the air flows if using a 2 can system so let it do whatever it is it wants to do and all we need to worry about is cleaning oil out before the vapors get to the intake.
Ok. So, is the check valve the part that attaches to the intake(plastic pierce that seems to break off)? If I were to only install one catch can should it be this line and not the other line to the turbo? I’m guessing I’d have to assemble my own and those that are made for our car is for the turbo line and not the intake line?
 

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Discussion Starter · #68 ·
Thanks for the thread. Good read. I have another question. I took if my intake tube, pulled the hose with the check valve to clean it. I noticed the clamp holding it to the turbo appears to be on backwards. Aren’t the slots supposed to line up with the black tabs on the tube and not over them? If so, it’s been like that since day 1. I flipped it around since that seems to be the correct way as the other end clamp was like this.
 

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Discussion Starter · #69 ·

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@R&T the line that has the check valve is where the oil comes from. If you look at how the stock lines are ran and where they attach and also where the BOV releases pressure into the intake it will make more sense as to why the problem exists.

The only place on a turbo'd vehicle that has vacuum when the turbo is spooled up if going to be directly in front of the compressor wheel on the turbo. PCV systems work on vacuum, The oil vapor is sucked out of the inside of the engine. PCV systems on an oposing bank engine works better then an inline engine because the entire crank case is able to evacuated where as an inline engine only the valve cover gets evacuated. What I mean by that is in order to suck out the vapors something has to replace them,. This something is air that gets pulled in by a vent line. On a "V" engine (V6, V8) The PCV or suction line is attached to one valve cover and the vent line is attached to the other valve cover. on an inline engine since there is only one valve cover both the suction lie and the vent line are attached at opposite ends of the cover.


A lot of people have an incorrect understanding of how the system works. The design is quite simple actually.

What are your thoughts when you see an air filter like this sticking up off the valve cover?
Car Motor vehicle Vehicle Automotive design Personal luxury car



If it's the PCV system has been deleted you are not alone. This is actually incorrect in a lot of cases. That air filter is there to filter air going in not coming out. If the ECM in the vehicle does not use a MAF sensor or the output side of the PCV plumbing is placed to it puts vapors before the MAF sensor then the PCV ystem will work without an issue.


In order to get air circulation inside the crank case you have to have air in and air out. With modern engines the air that goes into the engine for combustion needs to be measured to a correct amount of fuel can be added. That is why there is no air cleaner like the above photo on our vehicles. Ideally you do not want the PCV to put the vapor before the MAF because the oil will contaminate/foul the MAF sensor. but if it is places after the sensor then the air that goes into the valve cover would have to be metered beforehand. That is why we have the hose connecting from the valve cover to the plastic intake pipe.


This design works for the most part on NA vehicles until the vehicle ages and there is excessive ring blow by. On a vehicle that has a turbo problems occur.

As I said the only place that has a vacuum while under boost is going to be directly in front of the compressor wheel. This is where the PCV line from the valve cover needs to be attached.

Here is an image of our turbo.

Product Motor vehicle Automotive lighting Font Composite material



Now the BOVs function is to release pressurized air from the output side of the turbo. The turbo does not have brakes so if you have the car as WOT and there is 20PSI of boost pressure that pressure is located in all of the piping between the turbo and the throttle body. Now say you let off the accelerator, the throttle plate closes and the engine is no longer consuming that air. Remember the turbo doesn't have brakes built into it. It doesn't stop creating boost pressure so the pressure in the piping starts climbing. That excess pressure has to go somewhere. Because out MAF sensor is located before the turbo the air is metered before it enters the turbo so if that air pressure gets blown off to atmosphere the ECM is not going to have a correct measurement for the amount of air in the system. So that cannot be done. Instead the pressure gets blown back into the intake before the turbo.

That is the problem. If you look at where that pressure gets blown back and and where the PCV line connects you can see that the air pressure when blown back in gets blown right up that line and into the valve cover. GM designed the valve cover so it keeps oil from traveling down the line connected to the turbo but they did not design it to keep oil from traveling down the line connected to he intake pipe. because air is now going through the system backwards oil gets into the vent line. That crappy little check valve doesn't do diddly because oil does get past it. Eventually the valve gets gummied up from the oil and no linger closes. GM knew of the problem and that is why that crappy check valve was put there. It is also the reason why the crossover pipe was added onto the intecooler. That pipe is there to collect oil that condensates out of the vapor. If that tube wasn't there the bottom of the intecooler would fill up and would block the lower passages which would cause a pressure buildup inside the intecooler causing it to balloon.. All of this sounds really familiar doesn't it?

Instead of GM fixing the problem by redesigning the valve cover and putting baffles in it on that vent line they opted to add a crappy check valve and a small piece of hose. Those pieces only allow the system to function without any problems occurring for 36,000 miles or just past the warranty. After that 36,000 miles it is no longer GM responsibility to repair it, it becomes yours.

Now you can replace the check valve and buy some more time. The check valve does not stop al of the oil so some still makes it past. the check valve will also clog up again and get stuck. Adding the catch can does what GM should have done. It's adding baffles to the valve cover. The catch can is external but functions in the same manner.


Remember "IN" on the catch can always goes to the valve cover and the catch can MUST NOT have a check valve built into it.
 
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I want to note that how bad this problem is solely depends on how the vehicle is driven and if any modifications have been done that increase the boost pressure. If the car is grandma'd the majority of the time there is no excess pressure or high excess pressure that is getting blown backwards through the system. Tuned vehicles will have the boost pressure turned up and higher pressure = more oil moving backwards.

putting a fuel filter inline is going to restrict air movement through it. I don't know if that would be a valid way to test and see because it could restrict it enough that oil is not getting carried because of how slow the movement becomes.

I can tell you that I have oil in my catch cans. There are others that will tell you the same. I am running almost 40psi of boost and I drive my car hard which is why there is oil in my catch cans.

There are people that will tell you that there have no oil or as in the fuel filter example no oil is seen in the filter. How the vehicle is being operated has not been described and how many miles the vehicle has been driven has also not been told. If the car has only been driven 100 miles since the filter was put on doesn't matter if it has been 10 years or 2 years that is going to tell you why there is no oil evident. the car has been siting and not being used.

In a nut shell if there was not an oil issue then there would not be people having carbon buildup on the back of the valves. There is no other way the oil could get to the back of the valves unless it gets into the intake and how it would get there is from the PCV system. It's that simple. Lots of photos of Solstice GXPs with excess carbon buildup on the backs of the valves.
 
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Discussion Starter · #72 ·
@R&T the line that has the check valve is where the oil comes from. If you look at how the stock lines are ran and where they attach and also where the BOV releases pressure into the intake it will make more sense as to why the problem exists.

The only place on a turbo'd vehicle that has vacuum when the turbo is spooled up if going to be directly in front of the compressor wheel on the turbo. PCV systems work on vacuum, The oil vapor is sucked out of the inside of the engine. PCV systems on an oposing bank engine works better then an inline engine because the entire crank case is able to evacuated where as an inline engine only the valve cover gets evacuated. What I mean by that is in order to suck out the vapors something has to replace them,. This something is air that gets pulled in by a vent line. On a "V" engine (V6, V8) The PCV or suction line is attached to one valve cover and the vent line is attached to the other valve cover. on an inline engine since there is only one valve cover both the suction lie and the vent line are attached at opposite ends of the cover.


A lot of people have an incorrect understanding of how the system works. The design is quite simple actually.

What are your thoughts when you see an air filter like this sticking up off the valve cover?
View attachment 120147


If it's the PCV system has been deleted you are not alone. This is actually incorrect in a lot of cases. That air filter is there to filter air going in not coming out. If the ECM in the vehicle does not use a MAF sensor or the output side of the PCV plumbing is placed to it puts vapors before the MAF sensor then the PCV ystem will work without an issue.


In order to get air circulation inside the crank case you have to have air in and air out. With modern engines the air that goes into the engine for combustion needs to be measured to a correct amount of fuel can be added. That is why there is no air cleaner like the above photo on our vehicles. Ideally you do not want the PCV to put the vapor before the MAF because the oil will contaminate/foul the MAF sensor. but if it is places after the sensor then the air that goes into the valve cover would have to be metered beforehand. That is why we have the hose connecting from the valve cover to the plastic intake pipe.


This design works for the most part on NA vehicles until the vehicle ages and there is excessive ring blow by. On a vehicle that has a turbo problems occur.

As I said the only place that has a vacuum while under boost is going to be directly in front of the compressor wheel. This is where the PCV line from the valve cover needs to be attached.

Here is an image of our turbo.

View attachment 120145


Now the BOVs function is to release pressurized air from the output side of the turbo. The turbo does not have brakes so if you have the car as WOT and there is 20PSI of boost pressure that pressure is located in all of the piping between the turbo and the throttle body. Now say you let off the accelerator, the throttle plate closes and the engine is no longer consuming that air. Remember the turbo doesn't have brakes built into it. It doesn't stop creating boost pressure so the pressure in the piping starts climbing. That excess pressure has to go somewhere. Because out MAF sensor is located before the turbo the air is metered before it enters the turbo so if that air pressure gets blown off to atmosphere the ECM is not going to have a correct measurement for the amount of air in the system. So that cannot be done. Instead the pressure gets blown back into the intake before the turbo.

That is the problem. If you look at where that pressure gets blown back and and where the PCV line connects you can see that the air pressure when blown back in gets blown right up that line and into the valve cover. GM designed the valve cover so it keeps oil from traveling down the line connected to the turbo but they did not design it to keep oil from traveling down the line connected to he intake pipe. because air is now going through the system backwards oil gets into the vent line. That crappy little check valve doesn't do diddly because oil does get past it. Eventually the valve gets gummied up from the oil and no linger closes. GM knew of the problem and that is why that crappy check valve was put there. It is also the reason why the crossover pipe was added onto the intecooler. That pipe is there to collect oil that condensates out of the vapor. If that tube wasn't there the bottom of the intecooler would fill up and would block the lower passages which would cause a pressure buildup inside the intecooler causing it to balloon.. All of this sounds really familiar doesn't it?

Instead of GM fixing the problem by redesigning the valve cover and putting baffles in it on that vent line they opted to add a crappy check valve and a small piece of hose. Those pieces only allow the system to function without any problems occurring for 36,000 miles or just past the warranty. After that 36,000 miles it is no longer GM responsibility to repair it, it becomes yours.

Now you can replace the check valve and buy some more time. The check valve does not stop al of the oil so some still makes it past. the check valve will also clog up again and get stuck. Adding the catch can does what GM should have done. It's adding baffles to the valve cover. The catch can is external but functions in the same manner.


Remember "IN" on the catch can always goes to the valve cover and the catch can MUST NOT have a check valve built into it.
Thank you for the very thorough write up. And you were right, I always thought those filters on the valve covers were to allow air to escape pre pvc emissions era. Most cars 70’s and earlier that I’ve seen them on always had an oily residue on the filter and while running I’ve seen vapors/smoke coming through those filters many times but not always. Perhaps those motors had severe blow by like diesels get when boosted high and ran hard.

So, if I understand you, the line coming from the turbo to the side of the valve cover is suppose to pull air from the motor when under acceleration. When we let off the throttle the air then flows back to the motor and baffles inside the motor are suppose to prevent oil from coming down to the turbo even under boost? I’m The line from the intake to the motor is only suppose to allow air into the motor. That check valve is suppose to not allow air back into the intake but it does. I just cleaned oil out of my intake tube. Valve works great but obviously allows oil past it.

Ok, if I were to add a catch can, two would be ideal, but if I were to add just one it would be to the line connected to the turbo?
 

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One item on the crankcase ventilation system everyone is ignoring is the PCV valve in the LNF intake manifold.

There is a passage from the valve area to the intake manifold located between cylinder 2 and 4. There is a check valve in there to insure one way flow of crankcase vapor.

This passage allows crankcase vapor to be sucked out of the top of the head and into the intake manifold to be burned when not under boost, which is most of the time.

When the engine is not on turbo boost, the intake manifold is under vacuum, the PCV/check valve in the IM opens, sucking vapor out of the valve cover to be burned in the combustion chamber. Unfortunately, the vapor collects on the intake valve on its way to the cylinder, eventually coating it.

When you press down the accelerator enough, the turbo creates boost in the intake manifold, which closes the PCV/checkvalve in the IM preventing the air/fuel mixture from traveling into the engine.
 

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Sorry for the double reply but I wanted to ask you a question. Since you installed that in line fuel filter between the valve and the top of the motor, have you had any oil residue in your intake tube up to the turbo? Also, is your filter catching any oil residue at all.
No and no. I have had mo oil in that pipe since installing the fuel filter 'indicator' there. I suggest you thoroughly clean the vent valve.
 
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In order to add a catch can to be effective under vacuum, the intake manifold needs to be modified to stop direct passage of vapors from the top of the engine to the IM. The PCV/check valve needs to be removed from the IM and the hole plugged. Then a hole is drilled and tapped for a hose barb to remove vapor from the top of the engine and direct it to the catch can. The output of the can is plumbed to another barb installed on the IM, directing the vapor into the IM to be burned.

One catch can be plumbed to remove crankcase vapor during boost from the turbo side and under vacuum from the IM side with multiple check valves since only one side is venting crankcase vapors at any one period. The engine is either under vacuum or boost and can not do both at the same time.
 

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Discussion Starter · #76 · (Edited)
One item on the crankcase ventilation system everyone is ignoring is the PCV valve in the LNF intake manifold.

There is a passage from the valve area to the intake manifold located between cylinder 2 and 4. There is a check valve in there to insure one way flow of crankcase vapor.

This passage allows crankcase vapor to be sucked out of the top of the head and into the intake manifold to be burned when not under boost, which is most of the time.

When the engine is not on turbo boost, the intake manifold is under vacuum, the PCV/check valve in the IM opens, sucking vapor out of the valve cover to be burned in the combustion chamber. Unfortunately, the vapor collects on the intake valve on its way to the cylinder, eventually coating it.

When you press down the accelerator enough, the turbo creates boost in the intake manifold, which closes the PCV/checkvalve in the IM preventing the air/fuel mixture from traveling into the engine.
Where is the vapors routed from the pcv valve under the intake manifold? Is it pushed right back into the intake? Is the valve attached to the underside of the intake? I’ve never seen it and I know it’s somewhere under the IM.
Are you the one that showed how to do this a few years ago? I read that thread today. Very interesting concept and I’m guessing it works?
No and no. I have had mo oil in that pipe since installing the fuel filter 'indicator' there. I suggest you thoroughly clean the vent valve.
I did today twice with MAF cleaner and the tube with Spray 9. Not much oil was in the tube and the valve rattled perfect andI couldn’t suck air through it but could push air through it. Do you have anything else to keep the oil out of the compressor side of the turbo or just that filter mod? Have you had any issues related to that mod?
 

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Where is the vapors routed from the pcv valve under the intake manifold? Is it pushed right back into the intake? Is the valve attached to the underside of the intake? I’ve never seen it and I know it’s somewhere under the IM.
Are you the one that showed how to do this a few years ago? I read that thread today. Very interesting concept and I’m guessing it works?
Picture one shows the PCV/check valve under it's insertion hole in the intake manifold. You can see the smaller hole inside, leading into the manifold, The smaller hole will be plugged to stop crankcase vapor from entering the maifold.

Automotive exterior Bumper Font Composite material Auto part


Second picture shows the PCV/check valve in position.

Sleeve Automotive exterior Automotive tire Wood Font


Third picture shows the top of the manifold. The white dot is the planned location of the hose barb screwed into a drilled/tapped hole accessing the passage previously occupied by the PCV/check valve, which is now plugged at the outlet. Crankcase vapor will be captured there and routed out through the hose barb via hose to the catch can.

Automotive tire Motor vehicle Bicycle part Auto part Rim


From the catch can outlet, a hose routes the vapor to an external PCV/check valve then into the intake manifold. My plan is to split the catch cans output with a Y and route those hoses to two hose barbs, one barb located between passages 1 and 2 and the other between 3 and 4.

Reports on valve fouling describe the most fouling occurring on valves closest to the crankcase vapor insertion point, 3 and 4 on 4 cylinder engines. By locating the vapor insertion barbs at two locations on the manifold, the valve fouling should be equal on all 4 intake valves instead of concentrating it to intake valves on 3 and 4 only.

My GXP currently has 30,000 miles and not experiencing intake valve carbon buildup issues, yet. I bought the spare manifold to study and design a workaround for an eventual carbon build up issue in the future. I'll have the spare intake manifold modified prior to taking off the OEM manifold for walnut blasting when needed.
 

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Discussion Starter · #78 ·
Picture one shows the PCV/check valve under it's insertion hole in the intake manifold. You can see the smaller hole inside, leading into the manifold, The smaller hole will be plugged to stop crankcase vapor from entering the maifold.

View attachment 120155

Second picture shows the PCV/check valve in position.

View attachment 120156

Third picture shows the top of the manifold. The white dot is the planned location of the hose barb screwed into a drilled/tapped hole accessing the passage previously occupied by the PCV/check valve, which is now plugged at the outlet. Crankcase vapor will be captured there and routed out through the hose barb to the catch can.

View attachment 120157

From the catch can exit, a hose routes the vapor back to the intake manifold. My plan is to split the catch cans output with a Y and route those hoses to two hose barbs, one barb located between passages 1 and 2 and the other between 3 and 4.

Reports on valve fouling describe the most fouling occurring closest to the crankcase vapor insertion point.

My GXP currently has 30,000 miles and not experiencing intake valve carbon buildup issues, yet. I bought the spare manifold to study and design a workaround for an eventual carbon build up issue in the future. I'll have the spare intake manifold modified prior to taking off the OEM manifold for walnut blasting when needed.
Thanks for the pics. Very good idea and sounds like a solid plan
 

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Discussion Starter · #79 ·
Finally got everything squared away. Turned out to be a combination of carbon and the ecm. I had the gm intake and valve induction service done first. He said my pistons and most likely rings were pretty built up with carbon. The chemical is poured into the cylinders and left for a few hours. Normal build up the outcome is a tea colored liquid. Mine was closer to dark coffee. I also saw the residue on my intake manifold where it all wasn’t cleaned off. Then they run the chemical through the throttle body and let it heat soak for another hour or so. I noticed a difference from this when driving home. Much smoother acceleration and it does seem to pull harder and smoother idling without the burping that I had regularly. The crc I used a few times helped but it came back shortly.

After this was done he hooked up his scanner and test drove. Still getting all cylinder misfires but no noticeable misfires. All cylinders misfiring at the same time most of the time too. He did an injector test where he briefly shut off each injector and obviously felt that when performed on each injector. Injectors checked out fine. Next item to look at was the ecm. He replaced the ecm and did whatever programming was involved with that and voila no more misfires on the test drive. First time he’s ever had an ecm reading misfires that weren’t actually occurring. He’s been doing this since ‘77 and he’s had plenty of carbon issues especially with the 3.6 gm but has never had an ecm be the issue.

I had a nice talk with him before I left and found out gas plays a huge roll in the carbon issue and as luck would have it Florida has some of the worse gas in the country. GM actually sent an engineer here because the 3.6’s were getting warranty work on carbon issues as early as 5-6,000 miles. They called in a fuel engineer who tests fuel and what they found out was the fuel was considered well below what many other states are getting quality wise. He didn’t know the details of the fuel and what made it not so great. Also, on the carbon cleaners, gm’s cleaner is about the best you can get snd he’s tried just about all of them professional and over the counter. It’s better than BG, amsoil, etc,,, it’s not as great as what they once used but that cleaner was banned from use as it was considered very toxic. Catch cans can help some but won’t eliminate carbon buildup. There is zero chances of preventing carbon buildup on these motors other than having them cleaned every 10k or so. I was curious about how many times he’s performed this and he said a ton. The 3.6’s get so bad that he pulls the intake and actually floods the heads with the cleaner and uses zip ties to scrape off the carbon sometimes. Walnut blasting and dry ice is also great for removal he said but messy can be messy with the walnuts.
BTW, be glad you don’t have to deal with love bugs. 40 minute drive and I just washed her last night🤦‍♂️🤦‍♂️
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The gasoline will impact carbon buildup inside of the cylinders. Where the GXP is prone to having carbon buildup is on the backs of the valves. since the GXP is direct injected and not port injected the gasoline never touches the backs of the valves. On port injection the gasoline acts like a solvent and cleans off the backs of the valves, this doesn't happen with direct injection because the gasoline is shot directly into the cylinders.

You should have him read the write up I did on the PCV design problems, carbon buildup on the valves, oil in the intake tract and in the CAC (intecooler) and how to solve the problem without having to have the valve cover modified.

I can dig that up for you if you want. I would be interested in knowing what he says after reading it. There was another GM master tech that has read it and agreed with the diagnosis and the solution.
 
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