Getting Frustrated with Idle Speed Issues

**DBMaster** · 12-03-2007, 09:16 AM

OK, the short of it; I have a relatively new IACV (brand new part), fast idle valve, and related parts. The car is immaculate. I have set the idle speed three times by disconnecting the IACV, adjusting the idle speed, and resetting the ECU. Most of the time it holds the correct idle speed, but sometimes it wants to stay at about 1,000 RPM. That transmits a very annoying harmonic vibration to the pasenger compartment that makes waiting a lights a pain in the ass. My transmission is an auto. I have also loosened and tightened my motor mounts in sequence with no improvement in the vibration. It might be time for new mounts, anyway as these are ten years old (I replaced them in 1997 with about 150K on the clock and I now have 278K). That might help the vibration a little, but it won't affect the idle speed issue.

Am I doing something wrong?

***2oodoor*** · 12-03-2007, 12:39 PM

other things to check, advance and ign timing
also if the coolant temp sensor is slow to read or the thermostat is not holding temp, the ECU may be enrichening. If the idle is steady, you can try , last resort.... puting the E brake on, chock the wheels, put it in drive, have someone hold the brakes, then move the dist. around just a little till the vibration changes.

**DBMaster** · 12-03-2007, 02:37 PM

I like the distributor idea! I replaced the ECT sensor about a year ago and also had to replace the plugs due to broken wires. I think that is OK. My distributor is still original and I have a bad feeling that it may be causing the troubles. There's no cheap fix for that if I want to do it right.

Thanks for the suggestion. I'll check the timing and let you know how it looks.

**DBMaster** · 12-04-2007, 08:57 AM

I guess it had been too long since I checked the timing. It was a bit retarded (like me, apparently). I think the distributor is just about worn out, though, based upon the way the timing "bounces" a bit. I guess I should start shopping around. Once I got the timing set correctly the idle speed seemed to return to normal and the weird harmonic subsided. Thank you for the "dope slap."