I have an 87 Ford Ranger. If you start the truck and let it idle until it warms up enough to come off high idle, it runs great. If your in a hurry and do not let the truck get to proper operating temp before you take off, the truck with cough, sputter and engine temp will be higher. I have read codes and 31 appears. After reading that 87's have EGR issues and you can replace ECM with an 88+, I purchased an ECM from an 89 Ranger. After installing the ECM, the truck won't even start. Then I inspected the old computer and it specially has a Ford sticker for a 3.0 Taurus or Sable. Has anyone ever seen anything as crazy as this?

 

Well, mismatched computers can cause all sorts of problems. You can get away with it sometimes if the drive train configurations are the same. Could you get a computer for your car?

 

Yes, I bought a salvage yard computer from an 89 Ranger and the truck wouldn't even start. Put the 3.0 Taurus computer back in the truck and she fired right back up. I am guessing the salvage yard computer is bad but how do I tell?

 

Does the salvage computer run its self test?

Your original symptom seems to indicate that the computer is not properly compensating for cold conditions. So maybe the air or coolant temperature sensors are malfunctioning.

 

That is a good question. What self test?

 

I meant if you could pull the codes on the salvage computer?

 

I didn't even try. When it wouldn't start. I just reinstalled the 3.0 computer.

I will try that this weekend and get back to you.

 

I just remembered something else I fixed a long time ago. When the engine warms up, the computer goes into closed-loop operation, and starts looking at all the sensors to adjust fuel and timing. If one of those sensors is bad, the adjustments will be bad. In my case, the mass air sensor connector was not plugged in properly, and the engine ran very poorly when warmed up. There are other sensors, particularly air or coolant temperature sensors, that can also do that if they go bad. The temp sensors are cheap to replace. The MAF sensor may be more costly, but you might try a salvage unit.

 

I am gonna check the water and air temp sensors. In my case, once my truck warms up enough to idle down, it runs great. It's weird cause you have to stop and just sit with it at operating temp til it idles down though. I can get in it, take off cold and drive 11 miles to town. It will get up to temp and run like crap the whole way til I stop at a stoplight. Once it sits there and idles down, it's good to go til it gets cold again. Or I can start it and let it idle til it gets up to temp and it idles down, then it runs great too.