I have an 88 ford f-150 4x4 300-6 4-speed manual. The truck acts like it has a miss or vacume leak but I can’t find either. It spits and spudders until the fuel tank is less then 1/4 of a tank then it smooths up and runs fine. The check engine light comes on and goes off while driving but not at idle and the computer gives no error codes.
Just curious, but are you getting no codes at all or system pass 11 codes?
Sounds like a fuel pressure problem in reverse as in too much pressure.
Fortunately checking fuel pressure on your Ford at the schraeder valve is a VERY simply procedure.
Have you done it yet?
It is giving the pass codes. I have not done a fuel pressure check I don’t know the procedure.
Nows the time to pickup a Haynes manual and a fuel pressure gauge.
The Haynes will have the pressure specs and insructions for how to hookup the gauge.
The schraeder valve is at the top of the engine on the fuel rail & looks like a tire valve.
I don’t see what the 1/4 tank of fuel has to do with it, but you could consider a problem with the ignition module.
Your truck uses the TFI-IV module which has been prone to failures. Symptoms can resemble a fuel related problem to a tee.
There was a class action lawsuit against FOMOCO for these modules. A net search will reveal the details behind it.
Heat is what does them. The modules run very hot anyway and with warmer weather coming on that could ball that is needed to push it over the edge.
Well problem solved broken plug and a worn rotor button thanks for the feedback I learned a few things, I appriciate the help.
I’ve got a feeling we all learned a few things this time.
Thanks for the follow up.