ago in Ford by
I got a strange problem with my F150. When I go around 75-85km/hr the truck briefly loses power for about 0.5s. It's not always exactly at the same speed but always in that range. Kinda feels like hitting a small bump. This happens only once while accelerating past that point. Never at lower or higher speeds. Does anyone here have an idea what that could be? I had it in the shop and they said they couldn't reproduce the issue. I don't think they tried hard enough because it happens pretty much every time.

2 Answers

+1 vote
ago by
Thats not all that uncommon. There are a couple of things that could be wrong, clogged fuel filter, clogged injectors, bad spark plugs, dirty air filter, or a bad fuel pump. It's pretty easy to rule these out one by one, I'd start by checking the air filter and plugs.
ago by
Thanks! Great that is within my abilities. I was worried that it's something like my transmission or ECU failing (I guess that still could be the case). I will replace these one by one and see if it makes a difference. In terms of order, I guess this would make most sense (order by price/effort)?:

Air filter, fuel filter, plugs, fuel pump, injectors.
+1 vote
ago by
You could have a loose wire or one shorted to ground or another wire inside a harness when the air flow reaches that speed.... There is a wiggle test that you can perform..

With a volt meter with some long test leads.. You should probably start with this test.. https://I.Imgur.com/kvix0vq.jpg this checks the electrical connections...

Be sure to wiggle the wires that go in under the end of the underhood fuse box.. They have been known to come loose..

You may want to verify that the insertion and extraction force of the main relay in the underhood fuse box is not loose.. Do the same with the fuses..

You will also want to inspect the ignition switch pigtail ... Wiggling that harness with the engine running to see if the engine stalls..

The main relay supplies power to the injectors.. The various 12 volt devices on the engine like the oxygen sensor heaters. If one of the 4 oxygen sensor heater wires is blown by the wind at 80.. It could be shorting to ground before the fuse blows..

You could also have an issue with the ground side of the engine controls... Circuit 359 on the wiring diagrams.. It also is hooked to everything on the engine.. Except the injectors.. That is only connected to ground thru the computer.. I will have to look at the wiring diagram to see what color that wire would be.. There is a tsb about adding an additional ground connection usually back by the transmission harness on circuit 359.. Man did it change the way my 96 e250 ran ..

So with the engine running.. Start wiggling harnesses.. Start wiggling the wire into the connectors. Do only one section at a time..
ago by
Interesting. I will give this a go. Thanks!

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