Abnormal / rough idle

[Spooled]

My car has been idling very rough lately and I'm starting to wonder what the deal is. I wanted to see if anyone had any suggestions before I took it to the dealer. Here are the details:

+ Stock engine/turbo/exhaust

+ Turbo setup was replaced under warranty a few months ago for a bad wastegate actuator

+ I just put brand new stock plugs in with 0.031 gap on all thinking that maybe the NGK extended reach 7 series weren't getting a complete burn at idle. Nothing changed.

+ I did my best to check for vaccuum hose leaks with a spray bottle and soapy water, but that's not a guarentee.

+ I ran injector cleaner through the system with a half tank of gas.

Ever since I got the new turbo setup, there is a whistling sound from the engine bay under light load around 2900-3200 rpm depending on the day/temp/run time. The whistling sounds like a boost leak. The funny thing is that it sounds like it seals up after around 3100-3200 rpm. My theory on that has been that the BPV is bad. I wanted to know if that could possibly cause a rough idle? The air is getting recirculated, so I don't understand how it could.

The last thing is that I started it up and let the car idle for about 2 minutes, then shut it down without ever giving it any throttle. Then I pulled the plugs (the colder ones) and they were very black (carbon, not oil) and the electrode had so much carbon on it that at first it looked like metal shavings on a small magnet.

The car seemed to run considerably better after resetting the ECU before I did any of those things, but that was only for a short while.

So what does everyone think?
1. Boost leak
2. Bad BPV
3. Other vaccuum leak
4. Poor ignition system
5. Crank sensor (I doubt it cause it runs normal off idle for the most part)
6. Bad O2 sensor (I only have 31K miles on the car)
7. I should have bought a BMW

If it's a leaky vaccuum hose or BPV, then I'm not going to the dealer. I just don't want to replace all of the hoses and BPV and have them tell me that caused something else.

Thanks.

 

[computerGeek]

my idle bogged and was rough from time to time on the stock setup and then i changed my spark plugs and all was good! then 2 days later i added the hardpipes, CAI and SMIC and still all good!

i got the colder plugs from street unit

EDIT:: Gapped at 0.32

 

[Mr. Win]

how old are the plugs? id say clean them with some gasoline and try putting them back in if thier not to old. Stay with stock extended reach...

also you can try and pull the bpv out and see how it looks.

 

[peepsalot]

What about the bpv would you be looking for? How would that screw up the idle so much?

 

[miltont]

check your bypass valve
Maybe is loose

My car has been idling very rough lately and I'm starting to wonder what the deal is. I wanted to see if anyone had any suggestions before I took it to the dealer. Here are the details:

+ Stock engine/turbo/exhaust

+ Turbo setup was replaced under warranty a few months ago for a bad wastegate actuator

+ I just put brand new stock plugs in with 0.031 gap on all thinking that maybe the NGK extended reach 7 series weren't getting a complete burn at idle. Nothing changed.

+ I did my best to check for vaccuum hose leaks with a spray bottle and soapy water, but that's not a guarentee.

+ I ran injector cleaner through the system with a half tank of gas.

Ever since I got the new turbo setup, there is a whistling sound from the engine bay under light load around 2900-3200 rpm depending on the day/temp/run time. The whistling sounds like a boost leak. The funny thing is that it sounds like it seals up after around 3100-3200 rpm. My theory on that has been that the BPV is bad. I wanted to know if that could possibly cause a rough idle? The air is getting recirculated, so I don't understand how it could.

The last thing is that I started it up and let the car idle for about 2 minutes, then shut it down without ever giving it any throttle. Then I pulled the plugs (the colder ones) and they were very black (carbon, not oil) and the electrode had so much carbon on it that at first it looked like metal shavings on a small magnet.

The car seemed to run considerably better after resetting the ECU before I did any of those things, but that was only for a short while.

So what does everyone think?
1. Boost leak
2. Bad BPV
3. Other vaccuum leak
4. Poor ignition system
5. Crank sensor (I doubt it cause it runs normal off idle for the most part)
6. Bad O2 sensor (I only have 31K miles on the car)
7. I should have bought a BMW

If it's a leaky vaccuum hose or BPV, then I'm not going to the dealer. I just don't want to replace all of the hoses and BPV and have them tell me that caused something else.

Thanks.

 

[Mr. Win]

Peeps: well if theres a vaccum you leak big enough itll cause the car to feel like its going to stall out. If he thinks it could be the problem its a pretty simple one to knock out. Im not sure what the stock msp bpv looks like but you can generally adjust most or make sure everything all tightened up.

 

[computerGeek]

see pics for stock BPV http://www.msprotege.com/vbb300/showthread.php?t=93339

 

[Spooled]

The stock BPV is sealed and sucks. I've heard that they don't last long, but who knows. I was thinking more about a blown diaphram. Not really sure what the internals on one looks like. One reason I still think the BPV is going, even if it's not my main problem, is that it sounds different when spooling. Not really a lot louder, but it sounds like it's leaking somewhere (gurgles sometimes like someones hitting a bong under my hood). I've checked all the hoses, but if it's not sealed fully, then it could be venting some air.

The spark plugs in the car right now are brand new and are stock spec. they are gapped at 0.031". I like to be on the big side since I'm only boosting 4.9 psi, which brings up another symptom of a boost leak, BPV or otherwise. Obviously a boost leak wouldn't cause bad idle necessarily, but if the system after the MAF isn't sealed all the way to the intake manifold, air could go "missing" and run even richer than normal.

Here are a few more things that I forgot to mention before.

1. It only idles rough when the engine is warm and not choked.

2. If I'm idling and I tap the gas (ie - jump to 1000 rpm and let off), it dips lower than it used to before coming up to about ~500 rpm.

3. Pumping the brakes will almost stall the car sometimes. This is one of the things that makes me think there is a vaccuum leak somewhere like the brake booster line. I don't pretend to know anything about brakes, so I'm not sure.

 

[peepsalot]

Sounds like a vacuum leak to me. If the brakes are affecting your idle I'm gonna have to go with that. Good luck pinpointing it though.

 

[Spooled]

Thanks. I'm pretty sure it's something like that, too, but I really don't want to take it to the dealer again. Oh well, I guess they can change me oil for me while they have it.

 

[dirtysouth_msp]

Had a problem similar to this and the dealer replaced the Idle Air Control Valve and its thermo gasket (under warranty). After that, problem seems to be fixed. I did not notice anything with my brakes though.