While this has been discussed periodically

http://www.brickboard.com/RWD/index.htm?id=535708&show_all=2

I thought I would share my little adventure and save someone some pain. My current adventure's complete story is the subject of another thread

http://www.brickboard.com/RWD/volvo/1340712/220/240/260/280/hard_starting_rough_ridle.html

When I declare victory I will close that out. On with the Murder Mystery

Using Bentley's I was checking all of the likely suspects, to include the Coolant Temp Sensor that feeds information to the EZ-116K (ICU) and LH 2.4 computers. When I checked it that day, the car had been driven and I read the resistance off #13 in the LH harness. It was 230ish ohms. Close enough.

Moving on I checked the rest of the suspects/sensors. Nothing out of line.

Soooooo, frustrated like you read about, I start over. Maybe I missed something on that dark and stormy night.

This time, I check the Temp Sensor first. It just kept nagging me. Why was it running so rich at start, why the rough idle, why when it was warm did it behave, why why why?

Cold engine. Temp 55F
At #13 probe point in the LH, resistance was 112,000 ohms. WHAT!?
At #2 probe point in the ICU, resistance was 112,000 ohms. WHAT AGAIN!?

GO to the engine, pull the connector off, check each side of the sensor against a ground. Same readings. Okay everything is apart, good time to check the resistance across the harness and make sure there are no shorts to ground. .2 ohms per wire, no shorts.

RATS! Bad temp sensor. Explains a lot. Computers think the car is at the coldest place in the universe so it gives it more fuel and retards the timing.

Lesson learned. I should have made at least two measurements. One hot and one cold. With time, I should have warmed it up in the morning and taken measurements every hour to see how its doing against the curve and taken temp readings using a infrared temp sensor. One part of Bentley's sez take it out and test it at three temps. That sensor is a pain to R&R.

Hope this helps someone. Ordering in a new temp sensor. I swear I replaced that thing about 5-6 years ago, but the notebook doesn't record it.

Cheers.

R,
J.R.