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Discussion Starter #1
Ok, here's the deal.

low end boost works fine. When I hit the gas the boost engages up to maybe 6psi and then wants to go more, but wont. The engine is still making rpm's ok, then the check engine light comes on and the engine sputters just a bit but still runs ok, but I can tell that something is not working right as the engine just wont accelerate as smoothly and the boost is now reading zero. I drive around a bit with no other issues. Get home, take the battery cable off and let sit for a couple of hours, hook it all up again and all is fine. This repeats itself every time I try to take the boost over that 6psi mark.

I take it to my shop and it is checked for leaks, nothing found. MAF ok, Map ok, the tech checked the other sensors and found them to be ok as well except for one. He changed it with a new one. He writes this on the work order, "boost pressure reading a constant 14. Unplug the sensor and boost goes to 40 and jump it and it goes to Zero. replaced the sensor found the same reading. Connectors?

With that info what can you conclude? sorry, that there isn't anything more. I will print out all of your replies and take them back to him.

thanks, Tom
 

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Its a little difficult to keep up with the symptoms you are stating but let me try this

if it boosts to 6psi and then holds at that pressure, it is probably in limp mode light. The ECM has detected an issue that is not cause for immediate shutdown and repair but that falls into the catagory of "something is going on I dont like but I dont think will kill the motor" so it lets you continue to drive the car but at the reduced boost level.

This can be a result of a number of different issues. What codes do you pull from the ECM?

It could be a boost leak somewhere in the intake. Generally stock clamps coming loose have caused this result.

If you have an early GM Stage kit installed it could be the crimped sensors. They need to be soldered.

It could be bad fuel that is causing timing or mixture issues.

It could be a failed cam position sensor or servo. They can fail and the car will continue to operate but at reduced or zero boost.

How many miles on the car?

My wife's car went into limp mode light last spring when I brought it out of storage. I rebooted the car a couple of times and it has been fine since then.
 

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I went through this and there turned out to be a service bulletin on it. Recommended repair was to replace the intercooler. Under warranty, GM did this and the problem went away. Nobody could explain why, but it apparently was a recommended solution achieved through trial and error.
 

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There were two issues with the intercooler. The first was a small number of them were not correctly manufactured. The fins were not fully soldered to the cross tubes and they would over time baloon out - expanding in the middle - until they failed and leaked. These were replaced early as they all tended to fail quickly.
The second issue was with cars that had the GMPP stage 2 tune installed, a very small number of units had cracking of the intercooler generally at the sides in the metal can. These are difficult to diagnose until you get enough leakage to cause the ECM to react. Then you get codes and it will often go into limp mode. If you have this you can generally hear it upon startup if you are standing in front of the car and near the ground. Else you have to pull off a lot of plastic to gain access to the IC for visual inspection.
 

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Discussion Starter #5
Its a little difficult to keep up with the symptoms you are stating but let me try this

if it boosts to 6psi and then holds at that pressure, it is probably in limp mode light. The ECM has detected an issue that is not cause for immediate shutdown and repair but that falls into the catagory of "something is going on I dont like but I dont think will kill the motor" so it lets you continue to drive the car but at the reduced boost level.

This can be a result of a number of different issues. What codes do you pull from the ECM?

It could be a boost leak somewhere in the intake. Generally stock clamps coming loose have caused this result.

If you have an early GM Stage kit installed it could be the crimped sensors. They need to be soldered.

It could be bad fuel that is causing timing or mixture issues.

It could be a failed cam position sensor or servo. They can fail and the car will continue to operate but at reduced or zero boost.

How many miles on the car?

My wife's car went into limp mode light last spring when I brought it out of storage. I rebooted the car a couple of times and it has been fine since then.
, an

I have to get the codes from the shop, and ex-pontiac dealer Last year, I changed out the intercooler because the original one was struck by a small rock that put a hole in it. I believe that this began the problem, but the car was new to me and I never made any conscious effort to check the boost numbers. It just worked to my satisfaction with no issues. I had to clean the MAF for the boost to run in the low range once we had the intercooler changed. I cleaned it again this year before taking it out of storage. same as before. up to 6psi and then the CE light came on if I tried to push it a bit more. the car has 90,000 miles on it.
 

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Discussion Starter #6
I went through this and there turned out to be a service bulletin on it. Recommended repair was to replace the intercooler. Under warranty, GM did this and the problem went away. Nobody could explain why, but it apparently was a recommended solution achieved through trial and error.
maybe the intercooler connections need to be re-tightened. thanks
 

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, an

I have to get the codes from the shop, and ex-pontiac dealer Last year, I changed out the intercooler because the original one was struck by a small rock that put a hole in it. I believe that this began the problem, but the car was new to me and I never made any conscious effort to check the boost numbers. It just worked to my satisfaction with no issues. I had to clean the MAF for the boost to run in the low range once we had the intercooler changed. I cleaned it again this year before taking it out of storage. same as before. up to 6psi and then the CE light came on if I tried to push it a bit more. the car has 90,000 miles on it.
OK that helps

The MAF should not get contaminated under normal operations. If yours is getting dirty, ie responding favorably to cleaning, then look at the air cleaner and the piping upstream of the MAF. Is the connection to the intake tube just aft of the MAF intact? Frequently when the air cleaner is serviced this fitting is cracked or broken which leads to problems. Verify that its nice and tight. If its broken JB weld works well to repair it.

At 90k miles, the intake is probably has a lot of carbon buildup.

Read this thread

http://www.solsticeforum.com/forum/f11/direct-injection-carbon-build-up-article-vid-108817/

This is probably not the reason you are seeing limp mode but is is also probably an issue you want to address.

Since the problem appears to have been triggered by the recent work, verify that the intercooler is properly installed and has not issues. This may mean pulling off the shroud so you can see the entire IC. Open the drain hose and verify that there is no contamination in the IC itself. Look for water or oil. Let it drain well.

if you have not replaced the clamps with T clamps then take advantage of this opportunity to do so.

Pull the charge tube at the turbo and check for oil. If you are getting a lot of oil collecting there then you need to check the PCV valve and consider getting an oil catch can from DDM or Werks. Its probably a good idea in any case after you read the above link.

Pull the intake elbow at the throttle body and inspect the TB. It may (likely does) need cleaning. Check the rubber tubes and the intake elbow for cracks.

While you are at it, verify the integrity of the air cleaner box and the AC element.
 

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Dumb question, but what is 'electronic boost'?
 

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We really need to know if you he was experiencing was a CEL or a reduced power light. If he was seeing a flashing CEL, that normally points to a random engine misfire. If that is the case, he would need to start searching elsewhere for the problem. The CEL will only remain lit if the misfires occur enough to meet a certain threshold. Please get the codes read before performing any further diagnosis.
 

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Discussion Starter #11
OK that helps

The MAF should not get contaminated under normal operations. If yours is getting dirty, ie responding favorably to cleaning, then look at the air cleaner and the piping upstream of the MAF. Is the connection to the intake tube just aft of the MAF intact? Frequently when the air cleaner is serviced this fitting is cracked or broken which leads to problems. Verify that its nice and tight. If its broken JB weld works well to repair it.

At 90k miles, the intake is probably has a lot of carbon buildup.

Read this thread

http://www.solsticeforum.com/forum/f11/direct-injection-carbon-build-up-article-vid-108817/

This is probably not the reason you are seeing limp mode but is is also probably an issue you want to address.

Since the problem appears to have been triggered by the recent work, verify that the intercooler is properly installed and has not issues. This may mean pulling off the shroud so you can see the entire IC. Open the drain hose and verify that there is no contamination in the IC itself. Look for water or oil. Let it drain well.

if you have not replaced the clamps with T clamps then take advantage of this opportunity to do so.

Pull the charge tube at the turbo and check for oil. If you are getting a lot of oil collecting there then you need to check the PCV valve and consider getting an oil catch can from DDM or Werks. Its probably a good idea in any case after you read the above link.

Pull the intake elbow at the throttle body and inspect the TB. It may (likely does) need cleaning. Check the rubber tubes and the intake elbow for cracks.

While you are at it, verify the integrity of the air cleaner box and the AC element.
Hey Rob,

thanks for your input. It's all valuable to me.

today, I decided to take it for a ride, nothing special just 20miles up the highway and back. the entire time the boost worked very well as long as I didn't try to exceed the 6psi mark. It hit 6 a few times with no issues. So, then I get back home and figured that I would go into the back-roads and try to exceed the 6psi mark or cause the CEL to come on. Well, it would not go over 6psi, but kind of stayed there and I noticed that the (auto)tranny wouldn't shift into the next gear. After I let off the gas, the rpm's dropped and the car shifted normally when I normally accelerated. I pull up to another stop sign and try the whole thing again. Same result. The next intersection, no boost showing at all, maybe up to 1psi and then back to zero, no CEL, nothing. the car just accelerated as if it wasn't a turbo at all.

I looked back at some of my first threads and remembered this happening before.
http://www.solsticeforum.com/forum/f43/intercooler-changed-but-99642/

Having a bit more experience now behind the wheel makes me notice a few more details.

Any thoughts as I will be bringing it in Monday.
thanks, Tom
 

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Discussion Starter #12
We really need to know if you he was experiencing was a CEL or a reduced power light. If he was seeing a flashing CEL, that normally points to a random engine misfire. If that is the case, he would need to start searching elsewhere for the problem. The CEL will only remain lit if the misfires occur enough to meet a certain threshold. Please get the codes read before performing any further diagnosis.
the CEL is steady. I have to get a code reader for myself. keep reading and commenting though as all info is worth reading and considering.

thanks
 

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the CEL is steady. I have to get a code reader for myself. keep reading and commenting though as all info is worth reading and considering.

thanks
You can save some $$$ if you take the car to your favorite auto parts store (Autozone, O'Reilly's, NAPA, etc.) and have them read the codes for you. They usually offer this service for free.

Yogi
 

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No

The connection is between the ECM and the TCM

If you are getting hard downshifts, read the transmission succage thread. You may have failed cam servos or sensers
 

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True, but the trans shifting characteristics will vary dependent on engine load, rpm, and limp home status. So if you are still driving in limp mode, the trans will have limited shifting if you are easy on the throttle, but will not shift once you hit the limp limit as you previously described.
 

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Discussion Starter #19
True, but the trans shifting characteristics will vary dependent on engine load, rpm, and limp home status. So if you are still driving in limp mode, the trans will have limited shifting if you are easy on the throttle, but will not shift once you hit the limp limit as you previously described.
this all good info, really. it helps to give places to look at.

remember that I am going to print all of this out and take to the shop, so it would kind of like you guys are there discussing it with the people who used to sell and service the GXP. Let's see if they can figure this out from the info provided. Please keep it all coming. lol

thanks
 

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Discussion Starter #20
True, but the trans shifting characteristics will vary dependent on engine load, rpm, and limp home status. So if you are still driving in limp mode, the trans will have limited shifting if you are easy on the throttle, but will not shift once you hit the limp limit as you previously described.
would the limp home status also display a CEL? After the accelerator was floored and the boost tried to go over 6psi but couldn't, the engine and trans kind of stayed at that level until I let off of the accelerator. After that, the boost read zero and maybe tried to hit 1psi but fell off to zero. It would run through the gears as would a non turbo 2.0 might do, but I could feel that little bit of difference knowing what the turbo boost felt like. The thing is that there is no CEL at all.
 
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