OK, I really need help here . Warning, this is a bit long.

I bought a 1989 Ford F-150 4x4 shortbed with an EFI 300 6.

It had been sitting for years and had a bad rod bearing which I replaced inframe.

I started it, and it ran fair for a few minutes and got worse. I didn't think much of it as I was doing other things.

Symptoms:

The Truck will run decently for about 10 minutes if cold. Then it will gradually start to run poorly, and around 14 minutes it will roll and rattle at idle and die. A restart merits a virtually non-running engine. If you attempt to drive it after it first starts, it runs and drives decently. Once it is warm, it runs like it has a totally plugged exhaust

Here is what I have done to "fix it".

Drained tank as best I could, put in FI cleaner and about 1/2 tank of new gas.

Checked fuel pressure-50lbs. at the rail.

I unhooked the exhaust at the head pipes and started it, same thing. I don't think it is plugged.

Checked codes, none that I remember, now it won't give me any at all.

Set the TPS

Timing set

In a fit of desperation, I have taken to unhooking a sensor the night before I leave the truck and then starting it in the morning.

It does the same thing with the TPS unhooked, the 02 unhooked, EGR, coolant temp sensor unhooked.

I should note that I unhook the battery everynight.

My question is this:

Because the computer will not give up the codes, and it does run better with the spout connector out, is there a chance it is the computer?

I have intentionally not thrown parts at it, but I will if I need to fix it.

I don't know if it is a temp thing, or it just takes 10-13 mintutes to relearn the error that is causing it to run badly?

I have never been defeated by a car, but this one is close now.....It is consuming alot of my time and mental energy and I would like to move on.

Thanks for any help you may offer, ROB

 

Sounds like a bad (1)TFI module or (2)ECT sensor to me.

 

ECT=Engine cooling sensor on the front of the engine?

Regarding the TFI- Do they break down with heat over time?

Thanks, for the help, ROB

 

Good luck and have a nice day.

 

Any ideas on why it will not divulge the codes? I have done the jumper on the sti and other connector and it will not blink a code 11 or anything, both on the dash or with a test light.

Thank you, ROB

 

They could "still" be working in the computers eyes. It hits it with the test and it comes back in the parameters that allows it to run the test but not start the vehical.

 

It runs, but it will not give up the codes so I feel like I am shooting in the dark.

Thanks for the input, I do appreciate it.

Thanks, ROB

 

YOu may not be jumping the right ones to get the codes. The pictures are a little sketchy so you might try the connector right next the one you're jumping.

 

I'm sure I was jumping the correct wires. Hmmmmm!

I checked the CTS and it was within specs.

I also checked the TFI module using the chart in they Haynes manual. I checked the resistances and they were all within spec.

Hmmmmm!

Ideas?

ROB

 

There is a wire coming off the NEG (-) post of the battery, it is a Black wire with a green stripe and goes to a plug, an inline fuse looking thing (it is not a fuse) about 3 inches from the post of the battery. Then it goes to the EEC Computer pins 40 & 60 and is the ground for most Actuators.

This is about the most important wire on your truck and if it is not connected the EEC will not work right.

 

I had two loose wires there that went to the same plug. I "assumed" that they went to the neg post so I hooked them both up to the negative.

Was that a mistake? They were not hooked up before., but they had been attached to something because the wire was stripped back.....

Thanks for more ideas, ROB

 

Does it all work now?
Was one of the wires Black with a green stripe?
Was the other one Black and going to the body?
Can you get codes now?

Hooking a wire to the NEG post can not hurt, if it was a power source wire than what ever it was hooked to will not work, If it was a ground wire then you did good.

 

No codes. I found a black and a black/green wire hooked up to the core support by the battery.

I went ahead and hooked them direct to the battery ground.

It usually runs good when cold, but now it is running not so good even cold.

One thing I did not check when I was inside the distributor was the pick-up assembly. Does that go bad, and what are the symptoms?

I checked the TFI and it came out ok on resistance checks.

Thanks, ROB

 

OK, I pulled the computer and looked inside, all looks well in there, no fried transistors etc.

The truck is definately running worse now, like not at all almost.

I am going to diagnose the coil today and see what I can come up with there.

Any ideas on the pick-up inside the distributor?

Thanks for your help, ROB

 

Sounds like you disconnected the body ground, the body must be grounded and the Black green wire to the computer must be at ground also.