Weird problem...help

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Jul 22, 2005 | 09:39 PM

Blue69gt

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Weird problem...help

I have a 1988 F150 4x4 with a 94 Mustang ho 5.0 , topped by the original fuel injection system .Motor is fine I think, what is happening is after about 40 minures ,the truck develps a severe miss ,to the point that I can't drive it . It happened about a year and a half ago ,the fuel pressure regulator was changed ,it seemed ok for about 6 months ,then right back to the same problem, a second regulator was put in ,and since then I have had this problem .Truck has been sitting for the past year ,just tried today to get it running, started fine ,idled smooth ,drove it around the yard to lube and loosen everything up, then bang ,the miss was back again . compression is ok ,converters not plugged ,fuel pumps seem ok. Anyone had this happen? I am suspecting some kind of electrical gremlin, but where do I start? Thanks Mike

Jul 22, 2005 | 09:53 PM

Popa Tim

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From: Central NY

It sounds as if the problem occurs once the computer switches to closed loop mode, once its warmed up.

Pull your computer codes
Which computer are you using? the mustangs or your original?
Is the check engine light on? (I'm thinking O2 sensor)
Do you have a check engine light?
Check base timing (10 degrees)
Check your fuel pressure (32psi running, 39 primed) and vacuum line to the FPR.

Lastly, where did you get an exhaust manifold/headers for the mustangs gt40p heads?

Popa Tim

Last edited by Popa Tim; Jul 22, 2005 at 09:56 PM.

Jul 22, 2005 | 10:11 PM

Blue69gt

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thanks popa

I was dreading that it might be the computer .It is the original 88 one that came in the truck . I bought it with the engine already installed but I talk with the guy who I bought it from occasionally. I will ask where he got the headers ,I can tell you that they are long tube , I have two new fuel tanks and pumps that were put in just before I bought it . No check engine light ,in fact nothing appears out of the ordinary, oil pressure is normal as is temp .It's like there is a loose wire or something ,feels like it is only running on 6-7 cylinders ,engine makes a popping sound sort of...plugs ,wires all new when it happened the first time .Tanks were replaced due to rust and he thought they were the problem initially. The truck is at a shop now ,they are scanning it monday ,he is looking for suggestions or experiance with the same problem, thus I am here looking for answers....Mike

Jul 22, 2005 | 10:25 PM

Popa Tim

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From: Central NY

Is your tfi mounted on the distributor or the fender?
If its mounted on the dizzy have it tested, they tend to develope problems due to heat buildup there. Ford moved them to the fender with a nice heatsink in later years.

I wouldn't rule out the computer but It would be nearer the bottom of my list. They are pretty hardy.

As for the headers, verify that he didn't take the easy route and reinstall the 88's heads. The GT40P heads are worth a bit.

Jul 24, 2005 | 12:04 AM

Blue69gt

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Hey Popa ,talked to the guy today, he said whatever heads came with the motor are what are on it. It was pulled from a wrecked 94 Mustang and torn down/rebuilt. He bought it as a rebuilt ,got a year warranty , it was fine all that time . He doesn't know about headers other than they are dynomax installed by a muffler shop ,it has been 5 years since the swap was done . . The first instance of the miss in the engine was two yerars ago ,he replaced fuel pressure regulator which helped it for awhile ,then it came back sporadically until he just parked it....Regards mike