P0172, rough idle, and sputtering acceleration

I've spent the last 3.5 hours searching the forums, and I can't seem to find anyone who's having the same problem. I've had idle issues with my MSP for quite some time. I got a new car, so when the issue got really bad I just ignored it for a good 8 months. The car got to the point where it wouldn't idle itself at all. Finally got around to addressing that problem and checked out everything in the intake system. Cleaned the TB, cleaned and tested the EGR and IACV. Still had the problem, so replaced the IACV. That seemed to fix the problem... at least temporarily. Shortly after that replacement it threw a CEL (P0172). The car was still driving fine though, and actually turned itself off for a few days. Then it came back, but still no sign of a real problem. A few weeks of running with the CEL and I started to notice some worse than usual hesitation in the 3-4K range. Nothing terrible, but definitely a stutter happening when it got to boost. Everything went fairly quickly downhill from there.

I started having to manually idle the car every time I'd come to a stop. The damn thing just wanted to die nearly every time I put the clutch in. Next step was to replace spark plugs (it had been awhile, but they looked fine and I really don't think it was even necessary), cleaned the MAF, Sea Foam through brake booster line, and replaced any brittle vacuum lines. Problem is now just as bad as ever, maybe even worse. Today I drove to the gym without much of an issue. It tried to die on me a couple of times coming to a stop, but if I blipped the throttle a few times in quick succession it'd even out and idle ok. I went through a drive through on my way to work, and I couldn't get out of there without it dying. It was sputtering like crazy from a stop. I'd have to overrev it like crazy before I could let off the clutch to get moving. If I wasn't holding the RPMs to 2000-2500, it'd just die.

Any similar issues I've read about are linked to a P0171 code, so running lean rather than rich like mine is saying. Anyone got anymore suggestions of things to try out before I finally give in and just take it to a shop?

Thanks in advance!

Sounds like an exhaust leak, another lovely thing these cars tend to develop. Check that yet?


Edit: when you seafoamed it did you see smoke from the front of the car?
I could on mine. Leaked from downpipe/turbo gaskets.
When the car would idle it would sputter. When coming to a stop shifting to neutral AFR would hit 10-11 and stall it in most cases. Gas mileage went WAY down.

Do you have a wideband?

No, no wideband. The seafoam actually acted really strange. So when it first went in there was no smoke at all. Ran for a good 2 minutes without smoking. Then all of a sudden it started running incredibly rough, and yeah there was smoke coming from the front. Never could pinpoint where exactly it came from. Turned the car off, but something was still combusting as the engine kept running (barely) for a good 30 sec without the key in the ignition. Rolled the car out into the street, let it sit for a couple of minutes, started it up and it ran perfectly fine. All smoke came from the exhaust tip, as would be expected.

Last night I gave the filter a good clean, and actually remounted the Injen CAI into a SRI, and replaced the upstream O2 sensor. It ran better today, but still had some times where it randomly wanted to die, and I'd have to blip the throttle a few times to keep it alive. Just ordered an EGR valve as well to replace this weekend. Worth a shot. I guess I'll take a look at the exhaust tonight, and see if there's anything awry.

I plugged in an OBII diagnostic thing last night, but couldn't get any AFR readings from it. Didn't really take too much effort to look into that yet though.

How did you end up diagnosing the exhaust leak?

If its just an idle issue, try backing out the AAS screw on the top of the TB a little...I had to mess with this when i put in my twiggy cams last week....the TB has a throttle plate 'stop', don't touch that...the AAS is the philips screw head just to the right of the IAC if looking from the side of the car, and its the by-pass for the IAC...it won't raise your idle without jumping the diagnostics panel, but will change the IAC 'stepping' on the throttle lift...100% completely stopped my stalling from falling revs...

but, yours sounds a little bigger of a problem...i'd suggest renting a compression gauge and testing cylinder compression...with stock cams, turbo or not, you should have no problem with idle vacuum...and it seems you may have excessive blow by/lack of compression...if the rings are close to toast, a lot of different things can happen...and usually the first thing to exit the building is idle vacuum...

and...yeah, you need to try and figure out where that sea foam stuff is smoking out...thats a pretty relevant piece to this puzzle...its not between the block and cylinder head right...you're positive this isn't a head gasket issue?...no oil in the coolant, or coolant in the oil, etc.?

Installshield 2 said:

If its just an idle issue, try backing out the AAS screw on the top of the TB a little...I had to mess with this when i put in my twiggy cams last week....the TB has a throttle plate 'stop', don't touch that...the AAS is the philips screw head just to the right of the IAC if looking from the side of the car, and its the by-pass for the IAC...it won't raise your idle without jumping the diagnostics panel, but will change the IAC 'stepping' on the throttle lift...100% completely stopped my stalling from falling revs...

but, yours sounds a little bigger of a problem...i'd suggest renting a compression gauge and testing cylinder compression...with stock cams, turbo or not, you should have no problem with idle vacuum...and it seems you may have excessive blow by/lack of compression...if the rings are close to toast, a lot of different things can happen...and usually the first thing to exit the building is idle vacuum...

and...yeah, you need to try and figure out where that sea foam stuff is smoking out...thats a pretty relevant piece to this puzzle...its not between the block and cylinder head right...you're positive this isn't a head gasket issue?...no oil in the coolant, or coolant in the oil, etc.?

Click to expand...

I have a compression tester at home. I suppose that's worth testing just in case.

I was in the car at the time of the smoking, so I didn't see exactly where it was coming from. It came so suddenly, it was hard to see in the engine bay at all. It just strikes me as odd that it only happened for those 30 seconds or so, and then went back to normal. I also can't figure out why most people with similar issues are running lean, and I'm running rich.

yeah, the rich part is weird...

does your exhaust seem to work normally? Do you still have original cats, or any?...is there a noticeable smell of gasoline from the rear of the exhaust, and does it seem to be 'pulsing' normally?...also, if you pull the oil fill cap...can you smell a noticeable amount of gasoline or anything?...if it is cylinder compression, you often get a lot of gas in the oil system...you'll probably notice it right away if somethings up with that...

rich can come from a leaking injector, failing pressure regulator, or a block in the intake system some how...or may be electrical entirely (maf readings are off, etc.)...can you verify the VTCS system is working? When you start it cold, wait for it to warm up a few minutes, and watch for the arm to physically move it open...the VTCS is the system nearly up against the head on the intake manifold, its easier to see from the passenger fender area...maybe take a picture of what it looks like before you start it, then look back after it fully warms up...if that thing didn't move, it may be stuck closed or something...pretty rare chance this is the problem, but i'm just word vomiting easy things to check...

Installshield 2 said:

yeah, the rich part is weird...

does your exhaust seem to work normally? Do you still have original cats, or any?...is there a noticeable smell of gasoline from the rear of the exhaust, and does it seem to be 'pulsing' normally?...also, if you pull the oil fill cap...can you smell a noticeable amount of gasoline or anything?...if it is cylinder compression, you often get a lot of gas in the oil system...you'll probably notice it right away if somethings up with that...

rich can come from a leaking injector, failing pressure regulator, or a block in the intake system some how...or may be electrical entirely (maf readings are off, etc.)...can you verify the VTCS system is working? When you start it cold, wait for it to warm up a few minutes, and watch for the arm to physically move it open...the VTCS is the system nearly up against the head on the intake manifold, its easier to see from the passenger fender area...maybe take a picture of what it looks like before you start it, then look back after it fully warms up...if that thing didn't move, it may be stuck closed or something...pretty rare chance this is the problem, but i'm just word vomiting easy things to check...

Click to expand...

I have an aftermarket turbo-back, but still have a cat installed. Nothing seems odd with the exhaust... no changes that I've noticed anyway. The car is definitely running rich. We pulled the O2 sensor and torched if with some propane to see if it helped. Ran the car around the block a few times, came back and pulled it. The thing was black as black can be. Smelled the oil maybe 2 weeks ago, and there was no hint of gas or anything.

By VTCS, are you referring to the shutter valves in the intake manifold?

If you have an exhaust leak before the primary 02 that could cause you to run rich, have poor idle (overly rich), and cause the seafoam to smoke up your engine bay. Look at the cylinder head all around the turbo manifold to see if there is any black spots from an exhaust leak. You may need to deck the surface on the manifold and install a new gasket. Also, if you still have the stock manifold they are known for cracking between the #2 and #3 cylinder. Mine was cracked there and left a nice black line on the backside of the heat shield from the exhaust leak.