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1995 F150 runs poor when warm

My f150 looses power and sputters when it warms up. Let it cool off and it runs great until it warms up again. Check engine light comes on every now and then but not every time. Any ideas?

Until it’s found out why the Check Engine light is coming on it’s anybody’s guess.

Your vehicle has the OBDI engine management system. So you can’t go to a local parts store so they can pull the codes for you. Their code readers can only be used on OBDII engine management systems.

Here’s a link that describes how to pull the codes on a Ford with the OBDI engine management system.


I’d just add that this truck is also a TFI-IV ignition module equipped model. With warmer weather coming on and seeing as how these modules are prone to things like this then the module is always a suspect due to heat related failure.

The problem is that the check engine light does not stay on long eneough to test it. Is it possible to unhook one of the vacuum lines to get the check engine light to stay on. will it pick up both problems?

See what you can do about pulling that code anytime you have a chance. Doing something else to set it off won’t help.

Lacking a code you need to tell people stuff - like how old are your plugs & wires, fuel & air filters? The latter aren’t likely to matter so much. But sometimes the first sign of ignition components failing is problems when they get hot. So how much of your ignition system has been around since '95? (and who knows how many miles b/c you didn’t say).

Other than that I’d look for something making for an overly rich condition. A bad coolant temp sensor will have the computer leaving the “choke” on. A failing fuel pressure regulator will flood the engine & be most noticeable when it gets warmed up. Pull the vacuum line from the regulator and if you see any signs of gasoline in there replace the regulator.

I got ahold of an OBD1 and took the vacuum line off of the ERG valve to get the check engine light to stay on and it did pick up that and exhaust problems. I was told that it is my cat. Going to start there.

What were the actual codes? The report of something like a cat problem comes from O2 sensors. You don’t want to spend the $$ on a cat until you know you need one.

The thing is that sputtering when warm can also come either from a cat problem (partially clogged) or O2 sensor reading problems throwing off the fuel/air mix. So I’d just suggest spending some time (or $$ if someone else does it) checking the O2 sensor circuits and the O2 sensor operations.

Just curious, but did you run the entire test on pulling the codes?
There are 3 parts.

Not sure what the 3 parts are. I just removed the cat to see if that was the problem and it wasn’t. I replaced the ignition module and that was not it either. I replaced the o2 sensor and it ran great for about 100 miles. Then it started doing the same thing again so I exchanged the sensor thinking that it might have been defective but it wasn’t. Once aggain the check engine light comes on and off. It doesn’t stay on long. Not sure what to try next.

I did a complete tune up about two years ago when I had work done to the head. Also replaced fuel pump and fuel filter. Replaced the air filter back in January.

By 3 parts, I meant there are basically 3 sections of the test.

Key on, engine off.
First part is the static test. At the end of the static test there will be a pause followed by a separator code followed by another pause.
The second part comes after the last pause and is the continuous monitor, or wiggle test as it’s called. (This retains codes in memory)

The third part is key on, engine running. After a moment or two you will hear the engine rev up to a fast idle on its own. This is entirely normal and is the system doing diagnostics on itself. After the engine idles back down there will soon be some codes flashed. (This test checks a warmed up, running engine for any existing current problems.)

Code 11 in any of the 3 means a pass of course.

Ok I did all three parts, however it said it could not read codes when the engine was running and I do believe now that all of the codes it gave me were a result of me unplugging the erg. Is it possibly fuel related?

Did you ever check the coolant temp sensor or what? How about the fuel pressure regulator?