V6 Stumbles on Acceleration - F150online Forums


V6 Stumbles on Acceleration


Old 05-02-2004, 07:44 PM
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Join Date: May 2004
Posts: 108
V6 Stumbles on Acceleration

Greetings all

I have a 2000 F150, 4.2 V6 with 67k miles on it.. Here the problem im having.. :

Depending on how it 'feels' when it starts, acceleration may bring one of two results.. One- Normal... or two, cutting out, falling on its face on heavy accel. Light accel everything is hunky-dory. Even while driving, putting your foot into it will cause this stumble (miss, etc).

Sometimes.. every so often, the engine (when cold) will stand on its toes and be extremlely sensitive to the pedal.. you can hear the RPMS and feel it.. However, once the engine heats up, the power it gone.

It feels like it may not be getting enough fuel, BUT it varies depending outside temp and engine temp (usually everything is fine when engine in cool and or its cool outside).

No Check Engine Lights... No codes.

Also, When it is really hot outside, even some 91 Oct fuel (always with less octane) i'll get a 'pinging' on light accel while driving. Once at driving speed if I lightly press on the pedal it 'rattles' and pings.

Some have suggested the TPS.. some the MSF sensor (cleaned it).

Any ideas... I am considering replacing the TPS just for spite.

Thanks in advance!

Last edited by F150hasabug; 05-04-2004 at 12:56 PM.
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Old 05-03-2004, 12:01 PM
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Join Date: May 2004
Location: Tampa Fl
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mine did the same thing i changed the wires and plugs and that did it...even though tey looked NEW they were touching things like the dipstick and other metal items under the hood and shorted out...my mechanic friend found this on inspection and said i should change them out with MSD wires i did and no more bucking....try it its a cheap fix
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Old 05-03-2004, 12:10 PM
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Thanks James

I changed the plugs about 10k ago but have never the wires... Been meaning to do this though and think I will.

For clarification, what wires are the MSDs? Which would be the best wire for that engine, years, etc?

Thanks again
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Old 05-03-2004, 05:04 PM
Join Date: Oct 2003
Location: Mobile, Alabama
Posts: 22
I personally use only MotorCraft Platinum (made by Ford) spark plugs & plugwires.

I've been through 3 other sets of plugs on this truck (Bosch and some other brands) and only MotorCraft works 100% to my satisfaction.

I had a problem similar to what you were describing with my truck and it turned out to be a bad spark plug... and my mileage was terrible. I also had my EGR valves cleaned by a local mechanic for about $50 and this fixed my hesitation and acceleration issues.

Good Luck!


Last edited by DryIcez33; 05-03-2004 at 05:17 PM.
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Old 05-03-2004, 07:52 PM
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Im gonna change the plug wires and check the plugs... but it doesent feel like this would be the problem given it greatly depends on the engine temp and outside temp.. The hotter it is, the worse it behaves.

Thanks again for the info.. I'll keep ya'll posted.
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Old 05-05-2004, 08:50 PM
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Location: Ohio
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Let me know if you figure it out. My '97 acts the same way. It doesn't really run bad when it's warm but seems like the power falls off. Everything checks out OK mechanically but it definately runs better cold!
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Old 05-06-2004, 01:06 AM
Join Date: Oct 2002
Location: Columbia,MD
Posts: 39
whether it is the cause or not, this will still help, a bottle of redline fuel injector cleaner, miracle in a bottle, period. You will notice the improvment....i've tried a lot and this is easily the best
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Old 05-10-2004, 01:55 PM
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Seafoam! Awesome product indeed I only used the 1/3 pint recommented but did get a considerable amount of smoke (run the 1/3 pint through the brake booster vac - rest of the can into the gas tank).

The Seafoam did help alot. The engine is now quieter and is running smoother. The first thing I noticed is the brake pedal firmness is back.

I used $35 of good money to troubleshoot the TPS... that old one is good hehe. I re-gapped the spark plugs to .56 (instead of .52).

Next is to replace the plug wires - Last night when I pulled into the drive I could hear a 'ticking' sound coming from the engine (like an ingition arc), but when I looked under a dark hood I could not see any signs... the sound of the engine muffles it out when your looking under the hood, but when you stand beside the truck and its running the ticking is more pronounced.

The stumble on medium to heavy acceleration is still there though ... maybe the plug wires will help this... Although its not certain. I say this cause I CND when the engine is 'cooler'... only when its hot outside and the engine is at full running temp. The wires heating up and failing perhaps?

Saefoam is your friend! All the other injector cleaners, etc are teh suck.
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Old 05-14-2004, 11:35 PM
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Update: Well, the sparkplug wires seems to have fixed it! Woot!
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Old 05-16-2004, 05:51 PM
Join Date: Sep 2000
Posts: 58
Do any of you have the K&N air filter on there? I was having the same problem with mine. I took it to the dealer and got a diog on it. It also did not have any error codes. They told me it was the plugs and wires. I have 31,000 on my 2000 F-150 and did not think that was possible. I spoke with a friend of mine who is a ford tech. He said to check the mass air flow sensor. He said when people over oil there K&N filter it plugs up the sensor. So I went to autozone and bought a new one for 100.00 and put it in. It took me about 10 minutes. Now it runs like the day I bought it....perfect!! Hope this helps some of you.
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Old 05-24-2004, 10:57 AM
Join Date: May 2003
Location: GA
Posts: 29
It is strange, mine did the same thing, I found a fouled plug so I replaced the plugs and wires and it was fine for about 2500 miles and then it did it again. I then replaced the wires and plugs again and replaced the coil pack and the problem did not resurface.
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