I have taken my 98 ford f-250 v-8 5.4 L into a engine and a tranny shop neither can figure out why my truck surges when I am driving on the highway or when I am generally going over 35 mph and try to speed up. it surges when I try to speed up. I have replaced the fuel filter the mass airflow sensor the intake air temperature sensor and the idle air control valve. I have ran out of ideas. oh yea I have hooked it up to the computer you can get at shucks and nothing comes up. and I just had the tranny serviced also PLEASE HELP THANKS
What exactly does the truck do. Detail it. For a good shot in the dark, it could be one of the upstream oxygen sensors but I would ask for more details about the surging before I make that wild guess which could be wrong either way anyway. Then there is the throttle position sensor which doesn’t always show up with a computer code unless it completely cuts out and sometimes not even then.
when I am driving about say 30 and above and I want to speed up I start hitting the gas and the truck will jerk or surge forward as i am driving so I usually will hit the gas harder so it won’t do it so bad. the slower I speed up the worse it does it. When I was in idaho at school and all the way home on the highway it surged constantly unless my rpms were above 3k. since I have been here in seattle it hasn’t done it like that on the highway. it does it much more pevelently in idaho more specific Rexburg where it can get below zero.
I hope that can explain it a little more
Any chance there is a PCM update to cure this situation (not hardware but software)?
The statement “it surges when I try to speed up” this is normal,what I have experienced is when trying to maintain a steady speed the car slightly speeds up then lets back,a surge.
It sounds like you are describing a flatspot,you press the gas and initally nothing happens then the truck abrubtly accelerates,possibly fuel pressure related,hook up a gague (hopefully there is a test port)secure it to the windshield (facing towards you)and evaluate the fuel pressure reading when the flatspot and recovery occurs.
Like pleasedodgevan, I’m leaning (about 30 degrees to the left) towards a flat spot in the tps (throttle position sensor) more so than the fuel pressure.
You can check the volts and / or ohms on the tps as you smoothly, and slowly, move the throttle from idle to blast-off. You do the check with the engine off, ignition key in RUN. Here’s how: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152801e541b
You did not state the truck mileage but a weak fuel pump could cause this since the pump will be required to not only maintain a certain pressure at higher speeds but should also maintain it at an increased volume.
Another related possibility could be a faulty fuel pressure regulator (sticking).
Another possibility could be a vacuum leak or a fault in the EGR system (also a vacuum leak of sorts). In theory, an EGR fault should show up as a code. In practice, it may not depending on the fault.
Yet another wild guess (and I’m assuming this engine has variable intake runners) could be a fault in that area. Again, in theory a code should set, but…
If the truck were mine I would probably run a fuel pressure check (would show a fuel pressure reg. problem also) and throw a vacuum gauge on it as first steps. Many shops use a fuel pressure gauge but apparently few choose to use one of the handiest tools on earth; the vacuum gauge.
Those symptoms aren’t what I can help with except for Ford throttle position sensors used to be cheaply built. I had an 87 Tempo that went through three of them. Two were replacements not made by Ford. A bad computer is always a possibility to check on. The people who taught us about fuel injection would mention that the air ducting from the heat exchanger box to the throttle body had to be put on right or cold air would cause problems like yours.