YES, I have a RalliArt, but it is a TURBO and thought you guys would have more experience with this than the few of us turbo guys in the Ralli forums...
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About a week ago my CEL lit up and my idle has been real rough ever since. I borrowed a code reader and here are the results:

P0171 - System too lean
P0300 - Random/Multiple Misfire Detected

So I'm thinking it could be:

vacuum leak
fuel injector
spark plug(s)
MAS

Before wasting my time on any of this, am I looking in the right direction? BTW, only idle seems to be affected, I don't feel/notice anything while boosting or normal driving.

 

Vacuum leak is out of the question unless you had one before.
Fuel injector... eh maybe if it got clogged but i doubt it
Spark plugs could need replacing,gapping just check them
MAS - It would have thrown a code for it had it died

So I have to guess since your car's setup isn't familiar to me. Likely your running in limp home mode and clearing the codes out should get rid of the rough idle problem. I hope you have logging capability. You really need to check your injector duty cycle, knock count, and make corrections like heavy duty fuel pump, lower the boost, or reduce timing. :P

 

Thanks for the reply. I cleared the codes out with the scanner and it still idles rough, and by the end of the day, the same codes light back up.

I'll try the plugs first. Someone else mentioned they had the same codes and just ran SeaFoam thru their engine and prob was solved?!

 

Guess that means they clogged their injectors pretty badly. I'd recommend a bottle of techron :P

 

I don't understand why a vacuum leak would be out of the question. In fact I am thinking that a vacuum leak would do exactly what you describe - bad idle.

If you have a hose off someplace, air that hasn't been measured by the MAS, will enter the system throwing off the air/fuel ratio.

 

I'll check on this first to rule it out, or better yet find the leak!!! Thanks for your input!