Hey guys, I wanted to see if someone could help/ identify what is going on with my car. It’s an ‘05 Evo 8 (pretty stock). The car starts and runs fine for a while (over 20 min). Occasionally it will act bad during idle (and only at idle). When it happens the vacuum comes up to -10 and air fuel is normal to lean. The RPM drop to about 500 or less and feels like it wants to stall. If you apply throttle to get over 1500 RPM, the vacuum goes back to where it should (-19ish). Crusing feels fine decel will bring the vacuum back to -20. If you turn the car off for 5 minutes or more the issue goes away for a period of time. Yesterday on my way home it started again so I unplugged the MAF. It did change the way the car idled so I don’t think it is the maf. I question it being a boost leak seeing that it comes and goes but only at idle. I wouldn’t think a boost leak would go away and come back. Anyone else have this issue? Anyone have an idea that would affect idle and raise vacuum?

 

Check your IACV

 

Has someone been in the ecu? Did it just randomly start happening or? Sounds like you have a programing issue while the car is in closed loop.

 

It just started last week. I haven't done anything to it lately. The only thing that has an issue is the AC started to act up. The AC blows cold for about the same amount of time. I didn't have the AC on yesterday but the idle still acted up after a little drive.

 

Maybe also egr related.

May be getting stuck open

May be clogged.

How many miles on engine

 

I had a similar issue.

replacing my idle stepper motor fixed the problem for me. still having other problems tho lol

 

What does "pretty stock" mean?

 

Intake, licp, 3" front mount, TBE. All of which have been on the car for 50,000 miles. The motor has 145,000 miles.

 

Problem is still there. I have tried 3 different IAC and same issue. They seem to be moving as I unplug them and pull them out, they are sticking out. I'm going to try to pull the egr next. Any other ideas?

 

EVAP purge valve. It should stay closed until coolant temperature is up. And it should also close at idle. It could be sticking.

 

I found that it is the EGR system. I can pinch closed the air line attached and it idles much better. Is there a way to disable the EGR from cycling on once it's up to temp through ECUFlash?

 

just block it off.

 

having the same issue, thinking it's EGR valve as well...

 

+1