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1991 Ranger 4.0 stalls in gear, only when warm....


Coreybien

New Member
Joined
Sep 27, 2016
Messages
2
Reaction score
0
Vehicle Year
1991
Make / Model
Ford
Transmission
Automatic
I've been reading for probably the past week or two on everything I could pull up on google. I have tried a ton of things and done a bunch of testing and haven't been able to pinpoint the problem here, time for the description!

Just picked up a 91 ranger and was told it needed a new head gasket and water pump. I pumped up the cooling system and a heater hose was leaking as well as the weep hole on the pump. Changed the pump and heater hoses. When I got the truck it ran and shifted good, just ran a bit warm. I pulled the heads and had 2 cylinders on the drivers side that were cracked between valves and getting water in the cylinders. I got a new set of heads from clearwater cylinder head and popped those on with all new gaskets/o-rings/head bolts on the way back out of the motor.

Before I even changed the heads my problem started. The truck would drop rpms once shifted into any gear (R, OD, D, 2, 1) and sometimes it would rev back up and run but most of the time it stalls out. Sometimes it stumbles and dies, mostly it just cuts off almost immediately.

-I have cleaned the MAF, and tested the voltage/ground/signal voltage from the MAF and it seems in range. *When I unplug the MAF while running there's no difference in the idle though if that means anything.*

-Tested the voltage/ground/signal from the TPS and it seems in range.
-Tried a new IAC and it made no difference.
-Cleaned the throttle body.
-Checked ohms on the ECT sender to the computer and it was like 27 ohms cold and i believe 8 ohms warm.
-Thought it was transmission solenoids, unplugged those and no difference. Ended up putting a new TCC solenoid and 3-4 solenoid in anyways to rule it out and figured it would be a good time to do a trans fluid/filter/gasket service anyways.

The thing runs good, maybe a tiny bit rough in P and N but it doesn't stall.

I have read the ICM could be getting warm but that seemed to be more on the trucks with the ICM on the distributor, but the ICM on this is behind the passenger side headlight on this truck. But I didn't know how to test this and the autozones around me said they don't test ICMs.

ALSO it will shift into gear and drive fine when the motor is cold. Once up to temp I have my issue, but if I blip the throttle and shift while the rpms are just a little bit higher than idle it shifts into gear and doesn't die.

I think that's pretty much the majority of it so far, but if I remember anything else I will add it to this. Could it be a bad ICM? bad ECU? I didn't find how to test those so I haven't been able to check them yet but any advice on testing will be appreciated. I don't want to throw parts at it.

Thanks for any help!

Also I'm an HVAC tech here in Los Angeles so I will gladly help anyone with heating/ac/refrigeration questions and troubleshooting that you may have!
 


Coreybien

New Member
Joined
Sep 27, 2016
Messages
2
Reaction score
0
Vehicle Year
1991
Make / Model
Ford
Transmission
Automatic
Just drove to an autozone and the ICM tested good 3 times in a row
 

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