Spak plug mystery

I used to get that 'stumble and almost stall' with my 3.0L ranger, and my sister had the same problem with her Explorer (3.0L). Both vehicles are fuel injected, and flexfuel capable. I did the whole 100k mile tune up thing hoping that would fix things, but the problem persisted. I talked to a Ford mechanic, and he said replace the fuel pressure regulator and pump. The long and short of it is this; there are two regulators. One is on the fuel rail, and Ford calls it a fuel damper, the other is in the fuel tank attached to the entire fuel pump assembly. I had to replace both, now the problem is gone.

This may not pertain to your F-150, but it worked for me so I thought I'd throw that out there.

I've never had luck with Champions in anything other than my Jeep, and my lawnmower. My Fords run Motorcraft or Autolite plugs.

I don't have an answer to your question, unless you have a bad plug wire, or one of the new plugs is bad.

Spdloader

Remeber those 4 rules and life is a lot easier !!!

Amen. Well said TS.

Spdloader

re-installed

Yes, I did gap both sets of new plugs in fact that is the mystery. Both sets of correctly gapped plugs cause the stumble and the old plugs, which are grossly overgapped due to electrode wear don't cause the stumble. The truck runs great with the old plugs, crappy with the new plugs. The old plugs are back in right now. I suppose I should widen the gap of the new plugs away from factory specs and install them.

I've ruled out installation problems. At the same time I did the plugs I also installed new wires( Bosch) , cap , rotor and distributor ( unintended because cap screw broke in distributor ). To be honest, truck runs no different than before I replaced these items other than the new plugs of course.

Darn... I cant believe I spelt the title of this thread wrong. Anyway, I'll take your suggestion and have the fuel pressure regulator checked some time. This truck has 2 fuel pumps, 1 for each tank. Replacing those will require dropping both fuel tanks ... A major job ... big bucks .... Probably not worth it considering the age of this truck... I hope that isn't the problem.

Believe it or not, many years ago I had a college automotive instructor tell the class that Champion plugs came 10 to a package for a reason. That was because 2 of them would be bad right out of the box. Couple days later when we were tuning up cars someone brought in their new Champion plugs (10) installed them micr2 were bad.

Prehaps try replace 1st plug start the engine, 2nd plug start the engine, 3rd....etc...

See if the stumble gets increasingly worse as more new plugs are added, or if the stumbling is related to a specific new plug, or specific engine cyclinder.

You could have purchased 1 or more bad plugs. I've purchased lawn mower plugs before that were bad out of the box.

Because they're champions. Put motorcraft plugs in a ford. Not a GD mopar plug.

AMEN brother! and you can probably put the autolites with the bosh's.

The problem is definately gap related. For some reason, a wider gap ( away from factory specs ) fixes the problem. Maybe the high milage has something to do with it. Or maybe some ohter problem is rearing its ugly head , like a lean mixture, bad injectors etc... Still, there is a remote chance the both sets of new plugs were bad but I wouldn't bet the farm on it.

Luckily, a plug change on this engine is fairly straightforward. Since the first plug change a week ago, I've removed and replaced the plugs four more times trying to fix this problem. I would hate to run into this issue with the newer Fords. I've heard a plug change on those is a 3 hr job.

It's horrible. I wake up screaming and sweating just remembering it. The engineer that designed these things should be boiled in motor oil. James F. Hodgdon Jr. Hodgdon Scale Models