Questions and Answers
Surging F-150
Q. Hi Vince, I am an ASE certified auto, medium truck and auto parts technician, but I have one that has been eluding me for months!!!! It is a 1990 Ford F-150 2wd, 4.9 liter, manual transmission and has 143,000 miles on it.
Plugs, cap, rotor, wires, fuel filter, alternator, battery, all are new. Gives no codes, active or history, it has an intermittent surge at low speeds at times, other times it will stumble off idle, has low power at times, and if I let it idle for an extended period of time, it will run rough and miss occasionally and the check engine light comes on, but not every time. Yet no codes set. Hheeeelllllppp!!! I have had it to three different dealerships and no one can find the problem!!!!! Any info you can give me would be greatly appreciated.
Thanks,
BlaineA. Well Blaine, you must have a lot of faith in me to believe I can come up with something you haven't. I'll try to justify that faith if I can.
Surging is usually caused by a bad O2 sensor. If it is sending a wrong signal, the check engine light will not go on, but the computer will be operating on bad information. So I would check that for a possible cause.
Here's an odd one to look for, but I have seen a few of them. Locate the MAP sensor connector on the 12A581 wiring harness and check the condition of the connector. Check for an improperly formed female terminal spring members. This will also cause the surging you describe. And since it is a "soft" malfunction, it will not trip the light.
Additional Information provided courtesy of ALLDATA
