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Discussion Starter · #1 ·
I've recently been experiencing some odd behavior when pushing the car. it seems like the car is having trouble holding high boost. it seems normal at low pressures, but once I floor it and hit over 20psi the engine sometimes hiccups and the car briefly bucks. it isn't always noticeable, but sometimes I also notice a burning smell, like burnt oil or plastic or something, but my nose is terrible and it could be metal or ceramic.

it's also possible my mpgs are down slightly and Ive been thinking that power's felt down the last few months but haven't been able to confirm.

my gxp is a DD. i haven't been driving hard much with the bad weather in the NE, and I don't notice these symptoms when driving like a sane person.


any suggestions?

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Gotta love that Avatar. Has it always done this or has it been since the last time you filled up? could all be fuel related and that smell is unburned fuel / steam smell. Id take it easy until you burn thru that tank then try it again once the new fuel runs thru the system. might ought to check and see if you have thrown any codes too.
 

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Discussion Starter · #4 ·
Sorry, should have added more info:

-Ive noticed the smell for a few months, but it comes and goes. I hadnt noticed it in a little while before the below hiccups started occurring.
-The hiccups are recent, within the last 2 weeks. They only happen at around max boost, and are not noticeable any other time. Since I don't hit max boost very often, it doesnt happen very often.
-I (mostly) filled up yesterday but I havent had a chance to push the car hard enough to test the turbo under the conditions that have been causing the symptoms. I'm pretty sure the hiccups have spanned 2 different fill-ups, but can't be certain. I usually only buy Sunoco, Sun, BP, etc out of fear of shady gas stations, and I don't often fill up at the same place twice in a row (just the way it works out, I'm not paranoid about buying gas lol).
-There's no CEL but I havent checked for codes since I replaced the thermostat a few weeks ago. I've been having issues getting my el cheapo chinese knock-off bluetooth OBDII dongle to sync with my phone.

Something I forgot to mention- when the above hiccup happens I sometimes hear moving air from the engine bay. I've had the car long enough to know when I should or shouldn't hear air moving in the engine or turbo, and this is not one of those times. I will feel the car hiccup and at the same time a low SWOOOOSH as if air is fleeing the system. It only lasts until the engine/turbo "catch up".
 

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What year car?
How many miles?
Any previous issues or problems?

Eliminate the easy things.
Check the oil for level and any contamination.
Check the coolant for level and any contamination. Only when cold and with the filler / overflow tank the highest point in the cooling system
Pull the charge tube at the turbo and check for oil. Potential PCV valve issue.
Verify that all the charge tube clamps are tight, ideally replace the factory clamps with T clamps. See many posts on this issue.
Visually inspect the intercooler to verify that there are no failures there.
Visually inspect the vacuum hoses and connertors to make sure they are sound and connected. Pay particular attention to the connection on the air cleaner as many have been broken when servicing the air filter.

Put a reader on the OBD port and check for codes. There can be codes that do not result in a CEL that might indicate what the issue is.

Visually inspect the throttle valve for condition and cleanliness.

If you have the GMPP tune, check to make sure the connectors are soldered and not crimped.
 

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Discussion Starter · #6 ·
What year car?
How many miles?
Any previous issues or problems?

Eliminate the easy things.
Check the oil for level and any contamination.
Check the coolant for level and any contamination. Only when cold and with the filler / overflow tank the highest point in the cooling system
Pull the charge tube at the turbo and check for oil. Potential PCV valve issue.
Verify that all the charge tube clamps are tight, ideally replace the factory clamps with T clamps. See many posts on this issue.
Visually inspect the intercooler to verify that there are no failures there.
Visually inspect the vacuum hoses and connertors to make sure they are sound and connected. Pay particular attention to the connection on the air cleaner as many have been broken when servicing the air filter.

Put a reader on the OBD port and check for codes. There can be codes that do not result in a CEL that might indicate what the issue is.

Visually inspect the throttle valve for condition and cleanliness.

If you have the GMPP tune, check to make sure the connectors are soldered and not crimped.
2008 GXP
60,000 miles
had a bad thermostat that was recently replaced and the coolant was flushed.
Changed spark plugs and installed phenolic spacer a few months ago (Oct?)

I did back out of a steep driveway a few weeks ago and heard a heart-dropping metal clang as the front dropped off the dip onto the road. it sounded really bad but I didn't see any damage to the intercooler.

-Oil was changed in Sept or Oct but I can check the level and consistency.
-Coolant should be good as it was changed 2 weeks ago
-The charge tube is the plastic pipe that connects the intercooler to the turbo, right? I'll check for oil inside. If that's the correct pipe then the previous owner installed T clamps as it's got 2 on it right now.
-It's hard to inspect the intercooler as it's so low to the ground and under the hood hinge. WHat should I be looking for? I don't see it bulging, but I don't know where that would be or what it'd look like. There's been some damage to the heat dispersal fins since I bought it, but nothing i can see out of the ordinary. I had the car on a lift 2 weeks ago and gave the whole undercarriage a once-over but didn't see anything concerning (besides a leaking rear differential).
-What are the vacuum hoses? Are they located on the turbo, the manifold, or?
-I'll check the air box.

I havent been able to get my OBDII adapter working. it stopped showing up as a bluetooth device. This is more my expertise and I haven't spent much time troubleshooting. As of 2 weeks ago it was code-free, but who knows what's happened since then.

-will check throttle valve as well

-i have trifecta budget tune using stock MAPs


As always, thanks for the responses. cars are not my expertise, but i love learning (and hating paying others)
 

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Clutch for the smell....maybe even for the bucking.... I backed my car out of a parking spot last March, and thought my car was on fire!! It was the clutch....They smell different then any other clutch out there when they start slipping. I've never smelled something like it other then a car on fire. That's all I can relate the smell of the clutch too. Most of the time a clutch normally smells like hot brakes, but not on the Solstice....it smells like your car is on fire!
 

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Check the gap on your plugs. By the way which brand did you use. Hope it was the Delco OEM's.
 

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Discussion Starter · #9 ·
Check the gap on your plugs. By the way which brand did you use. Hope it was the Delco OEM's.
was the oem delcos with stock gap. .32 was it? I checked each one to ensure they were .32 or whatever.

it was the same gap as the ones I pulled out

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Could be your catalytic converter. I had a vacuum hose slip off and caused carbon to build up in my cat. Ran fine under low - mid RPM's but choked when I got into higher RPM's. I also had a bad egg smell all the time. If the cat isn't damaged but just gunked up then CRC 05063 Guaranteed To Pass will clean it up.
 

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I totally forgot about the clutch. I slipped mine once or twice and it is a very distinctive smell. that's probably it.
 

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Here is a reference on one intercooler failure mode with the GMPP tune. The can cracks on the side close to the fins


Reason for Intercooler damage / explosion - Saturn Sky Forums: Saturn Sky Forum

This area is hidden by the shroud and difficult or impossible to see unless you get under the car and remove some of the plastic shroud.

It generally results in "fluttering" or inconsistent running at startup and eventually CEL and codes related to boost consistency. It does not generally result in the smell you are describing which does sound more like clutch material outgassing.
 

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Check the Mass Air Flow meter. If it has become dirty, which is common for us to find. The fueling will be off under full throttle conditions and can cause the symptoms you are experiencing of a slight hiccup. Also, a dirty Air Flow meter will also negatively affect fuel mileage.

Pull the Air Flow meter out of the intake and get a can of MAF cleaner from your local parts store and clean it. Re-install and drive the car for a little bit and try a full throttle pull.

Hope that helps.
Dave
 

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Discussion Starter · #15 ·
thanks for all the replies. I haven't had a chance to do any poking around in the engine bay. Busy this time of the year!

I did get my OBDII adapter working again and the Torque app returned no engine codes. i'm not sure if that's a good thing or a bad thing. I'd rather it tell me what's wrong even if the fix would be a little more inconvenient or costly!

I avoid listing everything odd I notice with a used car and kept my recent experiences as specific and precise as possible. If i listed every time something odd happened when driving a 5+ year old used car I'd still be typing up my first car. I was, and am, trying to avoid throwing everything at a wall hoping one sticks so as to get specific answers, and without making my own wild suggestions that may negatively influence the direction of the diagnosis.

That being said, I was driving during my lunch break today and had a few hiccups when shifting gears. I was driving around at normal speed, barely requiring any boost at all with traffic lights every quarter mile, when the car started bucking a little bit immediately after changing gears. For example, I was at a stop light and made a wide left turn after it turned green and as soon as I shifted into 2nd gear there was a slight pause where the car almost lurched forward for a split second, then regained itself and resumed accelerating. Obviously I lifted my right foot during the shift and naturally i hit the gas in anticipation of the clutch re-engagement. It's when I hit the gas that the car basically paused for a half second, bucking forward a bit with momentum, before it started accelerating again. The same thing happened going into 3rd gear. it reminded me to a much lesser extent of when I learned to drive stick with the car bucking and hawing after every shift.
This got me thinking that I've noticed this infrequently the last month or so. With snow, ice, and plenty of rain the last few weeks conditions have not been ideal, and I didn't think much of it until now.

it's with this experience just over an hour ago than I mention something else that happened last weekend. During the end of an approximately 15 minute highway drive and continuing onto suburban streets I began having trouble putting the car into gear. I could pull the trans out of gear fine, but putting it into any gear with the clutch fully depressed felt almost exactly like how clutch-less shifting feels when everything isn't lined up yet. I would hit the clutch and pull out of gear, but upon shifting into the new gear it would seemingly hit a wall. I held the clutch in and put pressure on the shifter and a few seconds later it would pop in and work as normal. I got to my destination and the car sat overnight. The next morning the car felt fine during my 20 minute commute to work. Like I stated in my 2nd paragraph, under other circumstance I wouldn't have brought this up, but I'm more convinced now that this is more likely related to the symptoms in this thread than not.

The smell isn't always noticeable but when it is it has been noticed after shifting when driving normally and also when pushing the engine hard whether shifting or not.
 

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Discussion Starter · #16 ·
small update:
things have showed down a bit. I took the car to a mechanic and basically eliminated the clutch as the problem. mechanic checked the cylinders and ensured everything was functioning mechanically, however he wasn't familiar enough with the turbo system and wanted me to drop the off for a few days to diagnose.

that wasn't what I was hoping to hear. once it warms up I'm gonna look into the suggestions posted here and maybe take it into a dealership. the car still behaves exactly as described and still hasn't thrown a single code. ugh. I just want to know what's wrong

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Discussion Starter · #17 ·
gonna try and finally get my hands dirty this weekend.

I had another thought recently, as being idle makes u think, and over-think things... could a bad cat cause these symptoms? I've read of a lot of cat problems not throwing cel codes. also to me it sounds like a bad cat could back up airflow through the entire engine system, which feels like what's going on to me. one other thought is that the car often runs hot, about 210 steady with outside temps being 15F under very little load.

thoughts?

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Did you clean the MAF as Dave suggested?

Is the air cleaner choked?

All the intake clamps tight?

Jack the car up in the front and pull the shroud off the intercooler from the bottom. Its just a few fastners. Then do a good visual inspection of the intercooler for damage, cracks or leaks.
 

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Discussion Starter · #19 ·
haven't done anything yet. I'm planning on running through everything I can in this thread tomorrow. the weather's been terrible for 2 straight months. should at least be able to knock out the simple things to check.

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Discussion Starter · #20 ·
Jacked it up and had some personal time with my GXP:









So....thats the driver's side front bottom of the IC. those are holes. I can blow air through them. The IC is beat to crap after hitting every piece of debris on I-95 and 295 for the past year. Gonna pick up a replacement (anyone have one for sale?)

My buddy says a long-term air leak like this would eventually kill the cat, which would be the rotten egg smell i get every know and then. I hope replacing the IC fixes everything, but not holding out much faith. He also said the billed labor hours to replace the radiator, which is behind the IC, is about 1.5 hours (he didn't have billable hours for IC). Time to find a cheap used OEM IC and get to work...

I'm afraid to take the bumper off...it's so distorted and knocked around it may not go back together properly!
 
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