New to forum. I have a 1990 f250 5.0 4x4 auto. Have had this problem since I purchase the truck. As state starts hard hot or cold. When cold runs while and stalls then restart stays running but idle fluctuate sometime idle is ok, the stumbling rough idle is a lot sometimes, not as much others. When driving it shifts hard, almost like a bad shift kit lol..Here is all the things I have done replaced iac valve, map sensor, ect sensor, ecu, egr valve and position sensor, distributor cap, rotor, plugs, wires, tps sensor, also removed cats ( thought may have been clogged). None of this fixed problem.. Recently replaced ignition control module and made sure distributor was set in right. Made it worse, harder to start hot or cold? Also checked all vacuum lines no leaks. Actually if I give the truck a vacuum leak it runs better ? Am puzzled, am running out of idea.. Please help any other things could be that I missed.. Thanks

 

Have you pulled the codes even if their isn't a check engine light still check the codes.
On my 88 the reason it would be a hard start and rough idle was the fuel lines were clogged and after awhile burnt up my fuel pump.
Check fuel pressure just to be sure.
Trav

 

Have replaced fuel filter, checked fuel pressure is a constant 32psi.. Only codes have pulled is tps sensor can't remember what number was will pull codes again today and update.. in begin had egr and o2 code which also replace o2 sensor.

 

When you replace each of these parts did you clear the codes. On my 92 I forgot to clear the codes before running the truck and it still ran poorly till I cleared the codes it ran better (although in my case it didn't fix my issue).


Also did you verify the TPS is within spec. I installed a brand new TPS on my 88 and it turned out to be a bad part from the store.


When you did the fuel pressure test did you turn it on KOEO and leave it for a while to see if it has a leakdown?
Trav

 

Koer codes.
12 rpm at idle out of range
23 tps sensor signal out of range
41 1 hego (ho2s) sensor voltage low/system lean
2 no ho2s switching detected
33 egr valve fault/ not closing properly
52 ps pressure switch open

Wires are bare at ps pressure switch.. I am thinking might be bad ground at this point. Replace fuel filter as well.. replaced coil also.. frustrating truck!!

 

I would definatly check the tps sensor voltage key on engine off. It should be .9-1 VDC however .6ish is fine.


I wish I could remember which wires you have to check.


I would say that is the reason for your TPS code, 02 sensor lean code, and your idle code.
Trav