I have a 1992 F150 with a 300/6. On start up, it has a very rough idle and runs rich, and it's seems to be temperature dependant. On a 60 degree day, it may idle rough for 10 seconds. On a 30 degree day it may idle rough for 45 seconds. Definite temperature related. Once it gets past this rough idle, it runs great. The change from rough to smooth is not gradual, it's like flipping a switch. I was expecting the IAC to fix it, but nope. IDEAS??

 

Two sensors I would be inclined to check would be the ECT and then the IAT. They effect startup, idle and drivability. But the problem is intermittent. Pulling codes is suggested and do this on a warm engine. Perform the KOEO test first and post your findings.

Have you checked for vacuum leaks, checked those brittle, prone to crack nylon vacuum lines?
Have you checked the cap and rotor?

 

Since this problem, I've done a full tune up, including distributor, checked for vacuum leaks, and installed a new computer. It has not been road legal for a few years until now, so I wasn't able to take it anywhere have codes checked, but I will soon. This is an every day problem. Even on a 70 degree day, it idles rough for a short period of time. A 15 degree morning is a 2 minute ordeal... very rich condition. When I replace the IAC, I DID NOT clean out inside the intake. I was just told to check that as well. I will try to check it out and I will post my findings. This truck is barely broken in with 222,000 miles... a part of the family.

 

OK.. I checked the codes KOEO with the engine warm. I got the following codes: 111, 113, 118, 173, 327, 334, and 543. Also, I recently changed the ECT and the IAT. No change. I removed the AIC and cleaned the intake openings.. all appeared very clean.

IDEAS?

 

You've got codes for IAT, ECT, EGR, O2 sensor, etc With that many unrelated codes, I would be looking at the ECM, ECM ground, or the wiring harness to the ECM. I had similar issues rough idle issues on a '91 bronco with the 5.8. Tons of unrelated codes. Turned out the computer was bad, and a new computer fixed everything.

 

Any progress on your problem?