Hi!

My 2001 F-150 2wd, M50D, has very recently begun to stumble a lot under full throttle. It only does this when I'm on the gas hard, but at the bottom end of a gear, for example, pulling out from a stoplight in first, if I put the pedal all the way down it will buck and stumble, or any time I upshift, if I follow that with putting the pedal down to accelerate it will do it.

This has only happened since Monday, before that it wasn't doing it at all. Last night I swapped in a new fuel filter (and oil and filter change) and I really thought I had it solved. The problem got about 75% better. But it definately did not go away.

The engine is throwing NO codes -- my OBDII scanner won't find anything wrong.

My Haynes manual basically says check everything electrical or fuel related. Not real helpful.

Any good suggestions on where to start?

Many thanks!

-Sam

 

Well, I know this doesn't make any sense, but I think I've got it fixed!

I replaced the plugs and wires tonight, gapped the plugs at 0.054" like the book says.

Took it for a 10 minute test run and couldn't get ONE stumble! Felt like I had a bunch more power, too. (Well, it helps not to have it fall on it's face when I hit the gas, I guess.)

The old plugs were orange/brown and all gapped at 0.070"! I guess the P.O. (60K miles ago) must have thought the wider gap would give a hotter spark. Might have worked, too. I'll stick to the book values, I think.

Anyway, thanks all for the advice! ;-)

-Sam

 

Add your name to the list.

As I read your first post I was already thinking "plugs and wires".

Pretty common after 2 or 3 years, or 70,000-80,000 miles.

Glad you got it solved.

 

Well, the truck has 108500 miles on it, still had the "Motorcraft" branded wires, though with that big gap, I think the plugs had been replaced.

Runs great, now!

Thanks!

 

My plugs seem to be needing regapping every 40-50K or so. I took them out after buying the "junk" truck from a farmer, and they had .12 gap, and were all discolored. Even broke one off trying to remove it. I put new plugs in, and 50K later, I started to get stumble too. I regapped, no sweat, and bang, back in business.

Anyone else here experience the "ever widening gap"?

 

I believe that gaps will get greater the longer they stay in. This is due to a kind of erosion that takes place when the spark jumps the gap. We have seen some vehicles with upwards of 100,000 miles on them with original plugs and gaps so wide you would not think that it would run. These new fangled electronic ignitions will really throw a spark

tc

 

Yeah, I believe you guys are right.

Even though the platinum plugs are supposed to be good for 100,000 miles, I have my doubts.
Mostly based on my experience and that of others here.

My 2005 has 65,000 miles on it and I am starting to notice a rougher idle and a little hesitation. Both of which signaled new plugs and wires were soon to be need when I had my 2005.

I plan to replace plugs and wires within the next month or so.

I did use standard copper plugs in the 2000 model and they worked just fine thank you very much.

I pulled them after about 18,000 miles and they looked just fine. Gap was still good. I put them right back in.

I'm likely to use copper plugs when I do them in the '05. Way cheaper, easier to find and work good. If they last 25,000 - 30,000 miles, that'll be fine with me.