I posted this yesterday under a different heading, but received only one reply. Figure I'd try again, as I'm at my wits end at this point ; )
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Howdy,

My '89 245 idles very rough and occasionally stalls, but only when the engine is warm and the transmission is in gear (D, 1, 2). When in Park or Neutral, the idle is still a little rough, but the car never gets close to stalling. Sometimes the car starts right up again, other times it does not.

I'm new to car maintenance, and for better or worse I have taken it upon myself to solve this problerm. Thankfully I don't have to depend on this car right now, so I've just been working on it when time permits. I've tried everything that has been suggested here on the brickboard, but the problem persists. Here's what's been done thus far:

- Verified that all ground, hose and cable connections are OK
- Replaced air intake hose to fix vacuum leak
- Cleaned throttle body and air bypass valve (aka IAC I think)
- Replaceed Air Filter
- Replaced plugs, cap and wires
- Replaced blade-fuse
- Replaced RPM sensor
- Replaced engine coolant temp sensor
- Replaced thermostat
- Ran a "quality" injector cleaner through one tank of gas
- Replaced AMM (by previous owner 24 months ago)
- Replaced oxygen sensor
- Replaced fuel pump relay
- Replaced 561 ECU with a 951
- Replaced Ignition Timing Controller computer
- Replaced Fuel Pressure Regulator
- Replaced Fuel Filter
- Replaced In-tank Fuel Pump (including hoses and filter sock)

Other things worth noting are that the preheat hose is not attached, and the on-board diagnostics return 1-1-1...no error code.

I had the same problem last fall, and replacing the thermostat helped somewhat...but the problem returned in just a couple of months. Is it possible that the replacement thermostat went bad already? If so, what other problem might have contributed to this premature failure? Also, when changing the Engine Coolant Temperature sensor, I lost (and replaced) some coolant. Is it possible that an air pocket in the coolant line is causing this? Finally, might is just be a bad air bypass valve?

Any suggestions would be greatly appreciated. Sorry for the long post.

THANKS.

- Mark