F150 runs poorly when it warms up

ford
f150

#1

my 1995 f150, 4.9l, 212,000 miles, doesn’t burn oil, has been running great for 15 yrs no problems, recently when it runs for a while, 15 mins to 30 mins, it starts sputtering, lurching & smells like it is running to rich, will stall but restarts cools down runs fine, have replaced egr valve, idle air sensor, oxygen sensor & complete tune up inc. fuel filter, need help!!


#2

Didn’t that year have the TFI (Thick Film Ignition) module? Those are bad about overheating, and give the symptoms you describe when they do. The module mounts to the side of the distributor. You have to clean the mounting location good and put lots of heatsink grease on it and the new module. I think that Ford even did some relocation kits to allow you to mount it near the front of the hood, somewhere in cool airflow.


#3

I second Tardis on this. Great advice.


#4

the ignition module is mounted on the inner fender,
did these still over heat? what about the pick up in the dist. do they overheat?


#5

The TFI modules get blistering hot no matter where they’re mounted, even when the engine is not running. One can turn the key to the RUN position without the engine being started and the back of the module will fry bacon in a few minutes.
(Discovered the hard way one time when I did not know the key was on)

What would be a surprise would be if the truck has the original module and it made it this far.


#6

Just the TFI module that I know of, but almost anything is possible.
Yes, the fender mounted ones can still be trouble. If it lasted 15 years, then it’s done its time.


#7

changed the ignition module no difference… also tried removing O2 sensor, thought maybe plugged cat, no help.


#8

Since the TFI module is not the problem I suppose we’ll have to guess some more. Based on the symptoms it sure seemed like a module fault to me.

What about checking the fuel pressure regulator? A reg. that is leaking slightly would not be noticeable on a cold engine but could be on a warm one since a hot engine requires far less fuel to run than a cold one. Disconnect the vacuum line to the reg. and apply suction to it. It should hold; if not, the reg. diaphragm is faulty.

Another possibility could be an ECT sensor going bad. Most of the time these are borderline failures but if one really went stupid it could cause this kind of problem.

What about the fuel pump in this matter? Has it ever been changed? Just wondering if the pump is failing and the pressure is dropping too low for the F.I. system to function properly. Low fuel pressure can cause poor atomization of the fuel from the injectors (peeing off it’s called) and can cause rich running, stalling, etc.


#9

fuel pressure tests:
engine off- 50#
eng. run- 50#
static pressure held for as long as i checked ( 10 mins at least)

i do not have a vacuum pump, but with fuel pressure fine is it worth checking the regulator? can’t see how reg could be bad when pressure passes fine. also did fuel pressure test again after driving truck until it was running poorly.

checked engine codes
old codes
koeo: 122, 126, 211, 327, 542, 556, 113, 118,
engine running: 411, 129,167,225,536,632,411,129,

cleared codes & restarted truck ( was running poorly)
koeo: 539 (not in haynes manual) 111 system passes

engine running: 411, 129, 177, 225, 632,
what about map or throttle position sensors?


#10

if any one has any ideas , i really need help.
i replaced the ect. sensor, map sensor, checked tps sensor, idle air bypass , everything i can think of. if any body can help please respond


#11

very disappointed, there is no help when the problem is not easy! guess i am going to the shop!


#12

Just wandering if you ever solved the problem. I have a 1995 f150 that is doing the same thing.