Question about 1991 Ford F150

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My truck runs great most times but every once and a while it runs very rough like it has a miss. when running rough like this if I shut it off most times it i hard to restart if it dose at all. Those times I just gotta let it cool for a bit. any idea what could be wrong? I changed the map sensor, the control modulator, and the distributor cap.

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  • 24 Answers

Have you replaced spark plugs, wires, fuel filter. This also could be an injector issue. Try a fuel additive that will clean out the injectors and fuel system to see if issue continues. Another thing that can cause this on the earlier Mustangs is a bad O2 sensor or bad catalytic converter.

Posted on Nov 05, 2012

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6 Suggested Answers

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  • 2 Answers

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Posted on Jan 02, 2017

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  • 1 Answer

SOURCE: truck starts, dies. truck runs good some days,bad the next

I had the same problem with My 1990 F150 300 6cylinder 4x4.....I cahnged all the same things you did, finally I sprayed a can of Gumout through the throttle body and it worked and ran great. Now I add fuel injector cleaner to the gas and a regular clean with the gumout and the problem has'nt come back. Good Luck to you and hope it works!

Posted on Oct 06, 2008

wyatt1582
  • 453 Answers

SOURCE: 1988 ford f150 running rough

Might want to change o2 sensor's, If they are not sending the right single its tell the computer to dump fuel. 1988 was using a fuel density system.
(1989 came out with Mass air flow system)
Check this
I think it might have a TFI module that's not working right. Located under distributor. Its gray and about 4" long and if equip, you need a 4 or 5.5 mm tool to unbolt it. This was a common thing back in the 80's. Its been so long I can't remember if the 4.9 straight 6 had it or not.
T- Thick
F- Film
I- Ignition module

Posted on Apr 24, 2009

66 chrgr
  • 1011 Answers

SOURCE: 1985 ford f150 with 5.0 EFI running very rich

Check you coolant temp sensor ,If it is bad it will be reading{ 40 degrees below zero }and this will cause a rich condition due to the computer thinking it is that could outside, which requires more fuel .:)

Posted on Sep 22, 2009

  • 119 Answers

SOURCE: 1991 302 runs like it is chocking out, I have

is it idling high and you put it i gear it runs rougher and smoke black check your coolant sensor also connection or sensor itself and fuel pressure if high check for return line blockage also vacuum leaks make sure you have the right vacuum going to your map sensor you need to check right vaccum at idle going to your map sensor/

Posted on Jan 19, 2010

  • 447 Answers

SOURCE: 1989 F150 WITH 5.0LITER RUNS FOR AWHILE THEN SHUTS

If it doesn't have any spark when cranking over after it has died then I would look at replacing the ignition pick-up coil located inside the distributor. If it does have spark you may have a fuel pump that quits pumping fuel as the pump heats up. I'd check for spark first but I have put a number of fuel pumps in these over the years also.

Posted on Jun 11, 2010

Testimonial: "Is there a way to test a ignition control module? I have replaced it so can I test the old one I took off and can I test the new one I installed on the distributor without removing it?"

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