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bucking under part throttle cruise

 
  #1  
Old 04-23-2011, 09:01 PM
bigteal
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bucking under part throttle cruise

1995 5.8 f150. My truck has developed a slight bucking/ jerking under part throttle cruising in OD. Goes away at idle or under half throttle or more. Resent tune up with plugs, wires, cap and rotor. Truck has MSD coil, cap and rotor with Ford Racing plug wires. I was thinking maybe the throttle body needs cleaned. Any thoughts?
 
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Old 04-23-2011, 09:34 PM
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could very well be that the throttle body needs to be cleaned. thats real easy, i would get yourself a gasket, some carb cleaner, an old toothbrush, and try that first. another possibility is the egr valve.
 
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Old 04-24-2011, 08:10 AM
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This started about 2 months after I put the headers on. Might have knocked some carbon loose and it worked its way to the egr. It's not a harsh jerking, just an annoying little studder.
 
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Old 04-24-2011, 11:44 AM
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i didnt think of such a possibility, but you could be on to something. like i said, try cleaning the throttle body and go from there. i would bet that its covered in black crud if youve never cleaned it before.
 
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Old 04-24-2011, 03:39 PM
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What is the condition of your oxygen sensor?
 
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Old 04-24-2011, 07:06 PM
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Ok I guess. As far as I know, its the original with 111,000. My mileage is still around 15 mpg.
 
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Old 04-24-2011, 11:36 PM
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Same EXACT issue.....Please post your findings back here....New plugs, wires, dizzy cap, etc.....Still has the studder at REALLY light throttle.....Like its not getting enough fuel....
 
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Old 04-25-2011, 08:54 AM
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I had the same problem and found one injector was plugged and had fouled a plug.
 
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Old 04-25-2011, 11:06 AM
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Originally Posted by damcar View Post
I had the same problem and found one injector was plugged and had fouled a plug.
Good call on this. Eventhough you are getting good milage, the sensor should be replaced at least every 50k miles.
 
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Old 04-25-2011, 01:22 PM
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my 93 f150/302 has the same issue, not really bad just annoying
 
  #11  
Old 04-25-2011, 03:15 PM
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Me too, I got a can of SeaFoam aerosol stuff and took the two air intake hoses off, with the truck running and throttle held 1x above idle, sprayed in 3 second intervals alternating between each intake hole until the can was half empty. Turned it off for 5 minutes, then drove it roughly for about 2 miles and then after all that everything was good. Two to three weeks later the same problem came about.

When I did a tune up last October, I noticed one plug was fouled and I put that under a bad dizzy cap because the cap and rotor were so worn that shifting into over drive with any throttle caused the whole truck to shake violently. So that's what I thought, I haven't looked too see if the same plug is fouled again, but it's worth a shot.

I had the same problem and found one injector was plugged and had fouled a plug.
How did you know the injector was bad?
 
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Old 04-26-2011, 09:11 AM
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I was having this problem for a while and could not figure it out. So, I finally decided to get a "Motorvac" cleaning for the entire intake. Suppose to flush and clean everything. When I picked-up my truck it was just as bad as when I took it in but they said give it a day or so to workout the bugs. Never had to do that before but okay I'll try it. When it didn't get any better someone told me it could be my fuel filter since I had just replaced my front fuel pump. Changed that three times over a six week period but nothing. So I checked the cap and rotor and decided they could stand to be changed and did that.

Everything I tried kept failing to solve the problem so back I went to the shop that did the Motorvac and asked them to find what was wrong. They checked it out and said they found the plugged injector and the fouled plug. They also did a compression test and said my left side bank only had 60 psi and with 214,000 miles they thought my engine was shot.

After paying the $312 bill I got in my truck and left and to my surprise it ran just like it did when I bought it new. So now I am going to do a "Leak down" test on my cooling system to see if it may had a bad head gasket and if that shows nothing then I will do another compression test myself this time and see what readings I get.

With it running this well I think they were just looking to sell me a new motor for $5,000 but we will see.
 
 
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