1987 F-150 runs rough when warm

Tiny
DUFF
  • MEMBER
  • 1987 FORD F-150
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 1,370,000 MILES
1987 F-150 4.9L EFI, Auto Trans. Problem: Engine missis when warm like is is just failing and will eventually die if left at idle. Runs OK till it starts to warm up, about 5 minutes. I have replaced the fuel in tank pump, high pressure fuel pump, fuel filter and have checked fuel pressure regulator for fuel leaks and holding 20psi vacuum. Will check actual fuel pressure and operation today. Replace EEC relay, plug wires, plugs, rotor, cap, coil and TPS(comfirmed at 1.0v). Could it be the MAP or Oxygen sensor and finally does this truck have an IRCM or CCRM?
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Sunday, February 13th, 2011 AT 3:52 PM

6 Replies

Tiny
MERLIN2021
  • EXPERT
You are describing a system that starts having trouble going into closed loop(warm) operation, this is when the O2 sensor comes online, check that first.
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Sunday, February 13th, 2011 AT 4:07 PM
Tiny
DUFF
  • MEMBER
Per your previous suggestion I have replaced the Oxygen Sensor. I also checked the fuel pressure and regulator response. It seems to work fine with pressure at 55psi engine OFF and low 40's engine ON. I removed the battery cable to zero out the EEC memory and started the truck. It ran better but still misses. It idled high at start and then brought itself down to a normal idle rpm. While driving there was an occasional miss during warm up and then the miss got pretty bad. It really didn't like acceleration when it was under a load. It died when I drove up and came to a stop. End of drive test. What do you suggest?

Duff
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Tuesday, February 15th, 2011 AT 9:02 PM
Tiny
DUFF
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Could the miss fires be caused by the TFI Module of the Hall Effect Stater Assembly in the distributor? Duff
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Friday, February 18th, 2011 AT 2:54 AM
Tiny
MERLIN2021
  • EXPERT
If you can run it down to Autozone, they can test the module for you before you buy a new one.
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Saturday, February 19th, 2011 AT 3:35 PM
Tiny
DUFF
  • MEMBER
No Auto Zone parts house near me could perform the TFI module test. Purchased new TFI module and still no help. Found words on the internet to the effect that FORD had a recall for TFI and Distributor Stator assembles in the late 1980's. Seems heat from the engine was a problem so they moved the TFI to the fender to keep it cool. Put new TFI on rebuilt distributor and it runs better than before. Of course everything is new now.
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Monday, February 28th, 2011 AT 9:07 PM
Tiny
MERLIN2021
  • EXPERT
OK TFI is normally the problem, but the dist. Can also, If you could have tested first, buying a complete dist. With mod would be the way to go.
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Monday, February 28th, 2011 AT 9:52 PM

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