'90 Ram won't idle in heat

[moparman76_69]

I recently got a '90 ram 150 318/auto that was originally my grandfathers. The past few days in the 100 degree temps, the truck will start to not idle and you have to stay on the gas and two foot it to keep it running. The first time it did it, a storm cut through the area and lowered the temps and it started running fine. Today though it did it again and even after letting it sit close to a hour it still did it. Once it started doing it if I floored it, it would bog down then pop back through the exhaust and pick up again or die. Anytime I let off the gas it would stumble and either bog when I gave it gas or start running fine until I let off again. Anyone have any ideas?

It has the maintenance required light on and I ran the codes, but they don't seem to match up to our codes except for what I assume is the oxygen sensor. I'll have to find where I wrote them down.

[bakes]

whats your fuel presure when this happens ?

[turbovanman²]

Post up the codes, but I would guess coolant temp sensor.

[moparman76_69]

whats your fuel presure when this happens ?

Not sure, I do know you have to turn the key off and back on to get it to prime again. 90 was the first year for TBI injection on the full size trucks. I was kind of thinking maybe fuel pump, but that doesn't explain the fact that it runs fine at higher RPMs.

[RoadWarrior222]

Hmmm, I'd go with Simon's theory at the moment, but I'm thinking "Oh it was the first year for TBI" ... and first year of practically everything that went from carb to tbi or tbi to mpi they ended up raising fuel pressure in later models 'coz of percolation issues.

[moparman76_69]

Post up the codes, but I would guess coolant temp sensor.

12 37 51 42 55

I bought a manual, or course 12 and 55 are the same as our cars

37 - Torque Converter Clutch Solenoid CKT or Trans Temp Sensor voltage too high or trans temp sensor voltage too low

I don't know if this truck as a CKT or not since it is (should be) a 46RH

42 - Auto Shutdown Relay Control Circuit

I would think this would make for a no start but maybe not

51 - system lean L-idle adap at rich limit or system lean r-idle adap at rich limit

I think this might be my problem and I assume it is the O2 sensor since there is only one in this year truck.

[turbovanman²]

CKT should mean circuit.

Stuck ox sensor would definately mess up hot restart.

Auto relay could be the computer or a wire rubbed thru somewhere.

Trans temp, that could play a roll in idling too.

[moparman76_69]

I've been searching and saw something about the code 37 showing up but not causing a mil light if the truck isn't equipped with that particular trans or doesn't have the tow option for the temp sensor.

With the code 51 would that cause a limp mode for the computer? I would think it would ignore it if it seems stuck. Then again the truck seems to lean out and die, because you have to turn the key on and off a couple of times to prime it to get it to restart.