My Dad's 90 pickup has a few problems.You used to be able to turn on the key if the check engine light went out it would start and idle perfect. If the light stayed on it was hard to start and idled low until it would warm up them it ran great. My brother was the last to drive it when it ran right. It just started stuttering real bad while he was driving and shut off.

We end up thinking he blew the head gasket, pulled the head off had it resurfaced, valve job, new gasket. Recently the light stays on constantly and will not go out.....EVER. I put a new distributor in it and it starts alot easier but still has the same running problem. Whenever you try to give it over about 30% throttle it shutters real bad and will not rev up, almost like its choking the motor. I tried to pull codes but the check engine light never flashes. I tried hooking up an obd1 codereader and it stayed on constantly ever not running with the ignition off. It had 1 bad fuel pump so I replaced it with a new unit and blocked off the other tank. New fuel filter, fuel pressure regulator, and cleaned the injectors and rail. New coil, distributor, tfi, tps and plugs. This truck is driving me nuts. Just to clarify its a 1990 F150 with a 300 I6 and a stick.

Any help would greatly appreciated.

 

is the TPS set at the right voltage?


Jim

 

I did a test with a voltmeter and everything seemed good.
The truck had the air pump and egr system taken off but it ran fine after that.
I checked the ecu and the harness and everything looks fine.
I read a thread on here earlier about a guy who had the same startup issues with the check engine light. He replaced his engine coolant temperature (ECT) sensor and that solved his problem.
I can't seem to get a break, every time I think I find the problem it proves itself
otherwise. I wondered if maybe my Dad put something together wrong when putting the head back on but it all seemed straitfoward and he has never had a problem like that so I ruled it out.
Does anybody know what these signs mean?

 

Hold on. You've replaced all these parts knowing that you can't pull codes? Frankly, it sounds like the computer, for what ever reason, is in limp mode. Until you can get the comp to talk to you changing all these other parts is a waste of time and funds.

 

Everything I have changed out so far it has seemed to need. Except the coil and regulator both of which weren't my recomendation. The distributor was giving it some issues starting before, but the new 1 makes it start alot easier and without ether. The module went bad before all of this happened and had to changed. One of the fuel pumps was burnt up, so we were using the one working pump, thats why a put a new pump it. Also, this truck didn't have a tank control valve so I thought it was making the pump we were using weaker because it was pushing all the fuel into the other tank and I didn't think it was staying cool enough. Thats why there is only one tank in it right now. So far I am being led to the computer. I read a thread on hear earlier about a guy having the same problem and it turned out to be his ECU. I ruled out the ECT and MAP today so th ECU is the last thing on my list.

Thanks for all of the help guys.

 

im having the same exact problems anyone know where i can get a new ecu at other then a junk yard? or can i just have this one reprogramed? i dont want to buy one from a junk yard just because it could have the same or anyother problem.

 

Theyre about $120 from the parts store. However, make sure you get the right one.

 

hey all mine was my egr valve. replace that before you replace the comp.my truck runs like a dream now

 

The ECU has a power supply attached to it. That was my problem when it was in limp mode. As I recall it didn't cost much to replace.

Sorry, mines an ODB1, 1986

 

Finally solves.
It was the ecu. With a secondary problem of the distributor. Never really seen 1 go bad like that, just glad to have it fixed.

Thanks for all the help and info guys.