My '93 240 with 106K has some idle hunt issues that I'm a bit stumped on:

Symptoms:

-When cold there is some bounce to the idle of +/- 250 rpm or so.
-When warm, idle seems to drift slowly +/- 50 rpm.
-Idle also seems just a little rough, especially when cold.
-Difficult hot start unless I press the gas a little.
-Vacuum shows 15" with some unsteadiness.
-Occassional stalling

What I've checked:

-Cannot find any vacuum leaks. Intake gasket and throttle bottle gasket are new. I verified that the brake booster is not leaking, by pinching the hose. Local shop did a smoke test and found a cracked flamed trap, but that's been fixed. I did a propane search as well.

-New plugs, wires, cap & rotor, fuel filter 15K ago.

-Cleaned IAC valve 15K ago. It does click during the LH2.4 self-test, but I wonder if it is sluggish.

-New ECT sensor

-New Fuel Pressure Regulator

-O2 sensor voltage does oscillate between 0 - 1 volts, but if I create a vacuum leak to takes at least 10 seconds to begin oscillating again. O2 sensor is original.

-Cleaned Throttle body 15K ago. Adjusted linkages.

-Timing looks good.

-No CEL codes.

-CAM timing advanced +5 deg with VX cam

-Valves adjusted 15K ago.


Any ideas?

Cold start injector leaking? Faulty thermal time switch?

I don't think my car has either of those.

At this point, the problem isn't terribly bad. I think my wife picked up a bad load of gas, which might have been the whole source of the stalling problems. Now that a fresh tank is in, it seems better.

As for my idle complaints, I think I'm just going to have to see if it get's worse. Otherwise I'll be doing blind parts swapping. It could be the IAC. Who knows.

Your way ahead of me but just a thought: You didn't say anything about the AMM. Get yourself an trustworthy spare so you can swap yours out at any time.

Marty

Thanks. I had ruled out the AMM because the everything is fine off idle and with a bad AMM it is usually the opposite. It certainly would be nice to have a spare though.