The Car has been idling very rough lately. When looking at the engine, it is visibly shaking back and forth. I can't see any movement at the motor mounts, so I don't believe they're the problem. Scangauge reports that the RPM at idle is about 650-660. When I gently press the accelerator, the engine revs to about 1000 RPM and the shaking ceases. I installed an underdrive pulley yesterday, and was thinking this could have caused the issue. Is this pronounced idle just a minor annoyance, or a sign of pending doom? Video attached, but it is poor cel phone quality video.

Thanks

did u replace the belt too?

Yes, brand new belt, of the size specified in the installation instructions. (sorry, don't remember what it was off the top of my head)

any white smoke or liquid of any sort coming out the tail pipe?

No, no smoke, liquid, flames - nothing like that.

are the pulleys properly aligned?

it's a crank pulley... nothing really to align. if it was machined improperly (run out, etc) then the belt would slip off before it caused idle issues.

clean your IACV, and double check the voltage being shown by your scangauge. since you're underdriving everything, your voltages may be screwy (alt turning slower). you should be right at 12 when the engine isn't running and ~13.6-14.2 when the engine is running.

as best as I can tell... They look pretty straight but I've had a couple beers... Gonna double check in the a.m.

oooh damn, good call! I haven't cleaned the IACV or PCV the whole time I've owned the car, and it's been a while since I've done the MAF and TB. Hope it stops raining tomorrow...

Looking at the How-To, no mention of what chemicals to use. Obviously MAF cleaner on the MAF, TB cleaner on the TB. Brake cleaner on the PCV? there's no electronics in there, as I understand. General elctronics cleaner for the IACV

The voltage didn't seem too off when I was driving around earlier, but I'm not making the connection of why decreased voltage would cause rough idle - can you elaborate?

Thanks, everyone, for your ideas so far!

coils, computers, sensors, etc all like to have the proper amount of voltage applied to them.

low or inconsistent voltage will affect the quality of spark, the accuracy of sensor readings, and the overall function of the computer. if it's slow to make adjustments to the idle control valve, or is making adjustments based on incorrect sensor data, that can cause a rough idle. voltage readings point to the overall health of your electrical system.

cool, thanks for sharing! going to get cleaners and clear everything out today.

Whats your mileage? Is it during cold start ups? Once warmed up does the rough idling go away? It could be that you have to replace your intake manifold gasket... BUT it depends on your mileage. I have an 05 with just over 115000 KM and mine is due to be replaced and my car has similar symptoms.

A little over 43,000 miles. It is cold here, but it's idling rough when the engine warms up - when it's cold the engine idles higher and is smoother.

cleaned the MAF and PCV, not sure how to get to the IACV since my car is DBW, and the How-To depicts a cable controlled throttle. Issue is unresolved, so the question now is, do I need to worry about the shaking, or is it just an annoyance? I can live with it as long as the car isn't tearing itself apart...

Did you reset the ECU? Just throwing this out there. The car may need to re-learn itself.

yes, i disconnected the battery before cleaning everything, and let it idle for 15 minutes as has been suggested before, so it should've re-learned

I am having the same problem it started around 50k. Took to dealer, replaced the PCM no communication with the scan tool. Still having the same problem, dealer will not do anything unit SES light comes on. Will clean MAF and TB in spring when temps outside are better.

Your new pulley, was it a crank pulley? Was it solid or did it still have a harmanic balancer on it? Lots of us are having ruff idle problems. I just did my intake gasket thinking it would fix the problem, the idle is stronger but still shakes when down at 650-750rpm.

PS. There is no IACV on a DBW, this could be why it cant adjust the air flow fine enough to get smoth idle below 800rpm once there is a little play in the butterfly control motor/gears.

Over at the Genvibe forums they are starting to call them vibe........rators.