Stock 2005 EVO 8 Rough Idle
 

I'm the new owner of a bone stock evo 8. I recently installed an ACT Flywheel, Clutch, and Pressure Plate on it. After it was back together and I took it for a spin around the block and it ran fine, a couple hours later I started it up and now it has a rough idle. I ran some basic diag tests on it and noticed high fuel trims (20%). I went over the car again and double/triple checked EVERYTHING to no avail. There shouldn't be any issues, but there is and I'm out of ideas. If anyone has any insight to my issue, I would greatly appreciate any direction toward the answer. Thank you in advance.

First off, thanks for joining on the EvOM boards{thumbup}

Sorry to hear of the issue.

Im more suspension savy vs drivetrain, but not sure if the clutch replacement issue is tied to this rough idle unless its a vibration youre getting from the new clutch :confused:

When you say you checked the fuel trims, do you have an ECU log you can post up here so the guys can take a look at it? (we have a paperclip icon that enables you can upload varies file formats)

Make sure you don't have any vacuum leaks. Like the crankcase breather hose not attached to the intake. This will make the car run lean, and run high positive fuel trims if you're running a MAF.

Thanks. Unfortunately no, it's a hand held diag tool. It goes into every gear nicely and grabs the flywheel well. I did the relearn procedure for the ECU and It's Idling well. Just got back from a test drive and it's idling rough again...

Last time i changed my clutch i cracked the egr solenoid vacuum port. I didnt noticed much of a rough idle but it did throw a code. Might wanna check that because its really hidden behind the intake manifold

No vacuum leaks, throttle body is clean, throttle body seals are good, I cleaned the MAF, and all connections are tight and sealed. The crazy thing is after I pulled it into my garage, sat there with a ****ty idle checked the data stream (key on engine off) and noticed it went into open loop when I wasn't driving (stop sign, turns, etc...) so I decided to take it out again and record the data stream. When I stopped at the end of my driveway it was smooth as could be; Good trims, nice flat idle, and steady RPMs. Took it about a mile down the road and it's loping again with erratic fuel trims. I'll try to copy the vids from my phone.

the EGR solenoid is visually intact, the wire is connected and I have no codes so far.

Evo takes a bit to relearn idle after disconnecting the battery, though I've ever only noticed it with intake modifications on MAF cars usually.

Check for boost/vacuum leaks as noted above. Perform a proper boost leak test and make sure all the hose connections underneath the Intake Manifold are connected correctly. Which ACT flywheel did you put in the car? Shouldn't matter but I never ran anything really light (<12 lbs or so) in an Evo so don't know what effect it may have on drivability. Don't know where in NJ you are but there are a lot of us in the NE that can help you go back over it, or data log the car to get a better idea what's going on.

Another thing is you stated that the TB was clean, did you clean it. If so that's likely the problem. Been posted on here quite a bit over the years that cleaning the back of the throttle plate causes issues as the TB plate has a sort of dry lubricant/sealant on it from the factory, also could have a damaged/bad IACS or TPS.

Certainly wouldn't be the first time someone work on one thing and something else went bad coincidentally

I considered cleaning the Throttle Body as a possible culprit, and I know all about fixing one thing and another bites the dust, but the problem existed before I cleaned the TB, coincidentally the boost leak test is why I ended up cleaning it, and since the seals are known to go bad I replaced them as well. I also cleaned the pcv valve due to a slight hesitation to open. Every vacuum hose is firmly connected correctly (I label everything before I remove it and double check it with a diagram when I reassemble). I'm starting to think the MAF sensor may be jerking me around, I noticed it wasn't exactly clean after the Boost Leak Test. I followed all of the proper procedures to clean that as well. Thinking it might also be a potential culprit to my sloppy idle.

Alright, so the most recent thing I did was the pcv valve. When I tested it, it wasn't opening as easily as I would've liked so I figured at this point it can't hurt to clean this thing too. Started it, let it warm up, steady and smooth idle. Ok. Took it for a test drive, and it was well behaved during the ride and after I returned home and let it sit idling for 10-15 mins. I suppose it's fixed? I'm done with the damn thing for tonight. I'll post an update after a few more drive cycles. Thanks for all your help folks. It's appericiated. Hopefully I tracked the issue down. I'm still unsure if it's fixed or if the pcv was the bastard gremlin, either way I'll keep you posted. Thanks again.

When my MAF went bad, it showed up as random hesitating on steady throttle, minor hiccups under light acceleration. Idle was good though. Chased a lot of parts to fix ( coils, wires plugs EGR etc ) Putting a brand new MAF on immediately cured the issue. ( rock auto.com)

several threads on it but not clear that MAF responds to cleaning ( it did not on mine ) as it is a Karman vortex type.

Make sure the MAF is plugged in properly too, sometimes it looks like it is in but not really connected.