THSCC Forums

So the with the civic still not running, I'm getting a little nervous about the rough idle from the M3. For the past few weeks, it's been just slightly rough upon initial startup and unless I let it idle for a minute (only about twice now), it's fine. If not, then it wants to stall once the clutch is let out.

Now all of the sudden, the entire car is really idling rough, at idle, while driving, and there's no difference between driving and sitting in neutral slowly raising the RPM's. RPM's don't bounce around and fuel filter replaced about 500 miles ago.

I have a Peake code reader and it registers nothing. All that being said, are there any M3 issues specific to check? I was wondering if tranny/motor mounts may be the problem.

It's a 98 M3 sedan with 93k. The tranny mounts were replaced about 10k ago by K&E. The car has been tracked a few times, but has run great for the last 5k or so miles.

Ideas? Now back to the honda, see ya in a bit...

Phil

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Phil... Now I miss the ITR and the M3!!!
1990 Honda Civic SI

How old are the plugs and wires...or is the M3 coil on plug?

M3 is coil on plug, so wires are not an issue.

I doubt the motor mounts are causing the trouble- based on your description.

I don't know alot about M3's, but I would check for vacuum leaks in the rubber air boots and air bypass line(s)- that car is getting old enough that you have to think about the rubber parts aging and cracking.

Since the rough idle is mostly there when the car is cold- maybe the Idle control valve is bad, or gummed up???


Bret.

Yeh it could be the ICV. if dirty they can cause a fluctuating idle (which i guess you dont have) or just a wrong idle rpm (maybe thats why its rough? too low?) what rpm is it trying to idle at hot and cold?

i just cleaned my ICV a few weeks ago and its not bad. remove the airbox and alternator cooling duct, two bolts off the dipstick bracket/holder thing. then if you look rearward of the intake manifold you can see it ( the silver can thing). just pull it down (unplugs a rubber hose from manifold) and unplug the wires and hoses.

Then spray it out w/ carb cleaner. The reason i describe this is because you DON'T have to take off the intake manifold like a lot of the online DIYs say you do.

But first i'd find a shop w/ a real code scanner. I scanned mine w/ the Peake tool once and it showed no codes. Few weeks later i went to a real shop (Shade Tree) and they picked up like 14 codes. Shade Tree will scan your codes for free as well. There might be a clue in there.

Get a diagnosis yet?

Nope. My parents are in the final stages of building their own house and so far, I've been spending my time helping them. The idle is getting worse and it's looking more and more like what others are describing though.

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Phil... Now I miss the ITR and the M3!!!
1990 Honda Civic SI

I agree w/ Dan that it's the ICV. Clean it out and see if that helps. No cost here since it's just a remove, clean and replace. If that doesn't work, you can see the shade tree folks or Dave Davis, one of our club supporters and my favorite mechanic....

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Rodney

'08 Bullitt mustang, CAM 7
Autox VP '09-'10, President '11-'12, interim President 2nd half of ‘14
proud recipient of the Bowie Grey service award '12
Now just a guy driving a mustang....