jkrueger2020

My 92 accord has 238k mi and has had a low idle (in my opinion) ever since I've owned it.

Symptoms:
1. The tachometer shows typical warm idle at 550-600 rpm. (Sometimes get 650 on a good day but 600 is most common.) Steering wheel vibrates badly at this idle - especially when A/C is on but the vibration is there without A/C as well.
2. When driving the car, parking for 30 minutes, and then jump back into the car, when I back out of the parking space and press down on the clutch to shift from Reverse into 1st, the idle jumps up to about 1000 or so, then immediately drop as low as 400 rpm and then immediately jumps back up to about 550-600 rpm.
3. If I rev the engine to about 1000 rpm when warm, the vibration mainly goes away (though still not 100% perfect).
4. Last winter, I was driving to a job about 30 minutes away highway driving. Toward the end of the trip when I stopped at a light, I started occasionally seeing an erratic idle where the idle would constantly go up and down between 750 - 1500 rpm. I haven't seen this problem since winter / no longer driving 30 minutes to work everyday.
5. I've noticed the exhaust seems to have kind of a funny smell to it - smells kind of like when a car is burning coolant (I think - have only smelled that a few times). But the overflow bottle when cold has coolant at the low level which I think should be fine when cold. (Just had Valvoline change the oil and they said the level was fine).

What I've done:
1. Two years ago my mechanic said he cleaned the throttle body with Seafoam but that didn't really seem to help any then.
2. Two years ago my mechanic also said he adjusted the idle speed (pretty sure they said it was the cold idle though. Said the warm was fine but I wasn't so sure about that. I haven't taken it back b/c I don't want to keep throwing $$$ at this without results.
3. When I got the gearbox rebuilt / clutch replaced last year, the mechanic inspected the engine mounts and replaced one (I think the front) but said the others were fine. Car still vibrated though after the work was done.
4. Just ran a bottle of red-line fuel system cleaner through the car, but didn't notice any change at all from having done it. Seemed like a waste of money.
5. Changed the spark plugs and PCV valve a year ago but the car still idled low when warm.
6. Had the timing belt, water pump, and seals replaced. Also had someone adjust the valves.

So my question is what's causing the low idle? I've tried to read up online, but I don't really know where to start on this. Do I start with the head gasket and do a compression test? Is it a leak in the vacuum system? Do I just need to adjust my warm idle to make it run faster?

Thanks,
Jonathan

Lost Again

My two cents.........

Check the coolant level. Clean the tb, be sure to get the twp ports towards the firewall side. Clean the IAC and FITV, for this gen the air boost cleaning can't hurt.