I have an 87 F150 302/5.0L. Was running fine while driving but started to bog down and backfire as I started to leave a red light. Cold not drive it over 55mph (60 mph downhill) without it bogging and backfiring. Seems to happen when the throttle is wide open fast. Have slowly open the throttle and seems to kinda work.

Pre Problem replacements and maintenance:

• Replaced all plugs
• Replaced all wires
• Fixed Infector pigtails due to rodents
• Replaced Ignition Control Module
• fixed all wires that rodents had fun with.
• Set timing

Post Problem replacements and maintenance:

• Replaced ignition coil
• Replaces rusted out muffler (in case it was clogged; needed to replace anyway, top was blown out...)
• Checked Throttle Control sensor (manually with meter)
• Checked/Replaced MAP sensor (2.48 volts idle, 2.49 volts as throttle goes up and back down to 2.48; Replaced MAP 2.5 volts idle and 2.52 as throttle goes up and back down to 5.0 volts.)
• Check each spark plug wire with inline light tester, all working
• Replaced Fuel Filter
• Checked Timing, OK
• I have to use starter fluid to crank it. But it will re-crank/re-start after that
• The Idling fluctuate up and down, almost to a dying point
• Checked rail fuel pressure
  Ignition on: 38 psi
  Ignition turned off: 30 psi
  Engine Running: 32 psi
  Engine Running Regulator Vacuum off: 38 psi
  Engine Running WOT: 28 psi
  Engine Running WOT Bogging/Backfiring: 48 psi (needle gage would jump up and down)
  Engine Turned Off After Running: 15 psi

Here are 3 videos I took of the problem.

 

Sounds like to me you have the firing order wrong. Check it again.

 

Also, check/replace the MAP sensor, and get your cats checked for blockage.

 

Labnerd,

Already checked that, part of the PRE.... Previous owner had 4 and 5 crossed.

Everything was running fine. Then at a red light started to take off and the problem started. Could not go over 55 mph without bogging and backfiring....

 

No Cats, MAP sensor replaced, and muffler replaced.... Did not fix it....

Old muffler.....

 

Check the compression just for grins and giggles.

 

Just for the hell of it, loosen the distributor bolt , mark where the distributor is so it can be returned to the same spot. Turn it CCW a few degrees and see if it runs better. If it does it means the timing marks are not correct anymore on the crankshaft pulley. The pulley is steel hub on rubber on steel balancer and they sometimes slip which invalidates the timing marks. If you ever have a ford that squeals and cant be stopped by putting lots of new things in the belt system, good chance it is a failing/failed harmonic balancer. worth a look

 

Will give it a try.

Just Curious, the timing was set and was running well prior to the problem. When I check the timing again after the problem started, the timing did not change. Would a slip still cause a problem?

Thanks

 

Will see about renting a compression gauge this weekend and check it...

Thanks,

 

Is it possible that the EGR valve is stuck open causing it to try to idle while ingesting exhaust gasses?

 

Would that also cause it not to start unless you use starter fluid? Will will restart after that....

 

Is there a check engine light? An egr problem should throw a code.

 

Wiring diagram I am using....
No check engine light. No OBD1 connector, cut off by a previous owner. Guessing it was cut off when the engine was replaced.

I just got a OBD1 reader and Plug harness to see about re-wiring it back in. I found the wires and tried to wire them together for Code test, not luck. No check engine light came on. Tried with a meter and test light, Test light stayed on. Will be seeing if they cut the test engine light also....



Found OBD1 Wires....




wiring diagram I am using...

 

I don't know, just throwing spitballs to see if anything sticks. There is so many things that could cause some or all the symptoms. Did the truck ever set up without running for any extended period? If so could be some gunky gas stuff clogging fuel injectors. I don't believe that the timing chain has jumped a notch with it still being able to start at all. It may turn out that a rodent damaged wire somewhere is broken/shorted out. If that is the case you have a lot of testing circuits ahead. I can't find a diagram of the gen 8 f150's PCM connector, but there is one for a 1995 that should be the same, both 60 pin and the associated wires should be the same that might help ohm out some circuits.I'll put the link below. Good Luck

https://troubleshootmyvehicle.com/fo...-pin-out-table

 

No CEL could be no bulb / blown bulb. does it come on during computer self test when the key is first turned on?