196k miles 2.2 vtec manual trans, runs smooth good gas mileage no other driveability issues. spark plugs were changed in October. At start it idles at 1500 rpm and is perfectly smooth. Once the temp gauge starts to move and idle drops to about 750 rpm, there is a pretty consistent vibration I can feel in the steering wheel. I would compare it to a front tire needing a balance or a very slight misfire. Not terrible, but consistent and noticeable. If rev it at all even just up to 1000 rpm it goes away. It feels like the idle should be fluctuating a bit at 750 when I feel the vibration but it just sits there and does not budge.

any ideas on what I should look at would be greatly appreciated, thanks!

 

Pull the spark plug wires, are they oil free? If oil is on the boots check that the spark plugs are tight and the oil seals are not leaking.
Move on to the cap and rotor, after some miles corrosion or 'boogers' can build up on the terminals, make sure they are clean under the cap and the rotor is not corroded. Check for oil under the cap.
Check that the sparkplug wires seal on the cap & plugs.
Pull the plugs and verify gap.

 

thanks for the info, mike. i was thinking that i should check the ignition components first.

i was planning on buying wires/cap/rotor/coil and replacing all of them as maintenance, i have no idea when they were last changed. at least 40k miles since that's how much the previous owner and I have put on the vehicle, and he said that none of those parts were changed while he owned it.

any specific brand recommendation for these parts? also any idea why the problem would be showing itself in such a limited situation?

 

compression checked, all in the 150's. changed plugs/wires/cap/rotor/coil, no oil in the tubes - seals were changed last fall. there was a little corrosion on the coil, nothing terrible. the wires were original per the date code.

the vibration feels a tiny bit stronger but is much more consistent, if that makes any sense. before, i would feel what i would describe as a small miss every 6-8 seconds at warm idle. the idle is smoother, i feel a little fluctuation every once in a while. i don't know if there really is a 'problem' or if it is normal for an engine with ~200k on it.

my next guess would be a motor mount. the front and driver's side mounts have been changed - the front one was bad, and the side one was changed when i had the tb/wp done last fall.