it will only gain speed slowly
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Senior User
Joined: Feb 2004
Posts: 236
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From: Guayaquil
it will only gain speed slowly
2WD EFI 4.9 6 cyl F-250
HEre's the story...
I turn on my truck and I have to give it some gas or it turns off, It stopped doing it automatically when cold some time ago. It doesn't matter if it has been run for a while I still have to do the same thing when I turn it back on so it is not a temperature issue. After giving it gas it will be good at idle and no problems will be present until I give it a lot of gas at parking or on the road, It won't accelerate, it feels heavy and it sounds like fuel or air is being interrupted, like if the combustion was not continuous. It gets worst when the AC is on or when I go from Drive to Neutral or Parking or the opposite. It will ONLY gain speed by doing it slowly and continuosly not pressing the gas at its maximum. Distributor cap and rotor, spark plugs and cables, vaccum connections, injectors, fuel pump have been checked, also the alternator voltage and no check engine light is present!.
Any ideas???
PLease help!, thanks a lot
HEre's the story...
I turn on my truck and I have to give it some gas or it turns off, It stopped doing it automatically when cold some time ago. It doesn't matter if it has been run for a while I still have to do the same thing when I turn it back on so it is not a temperature issue. After giving it gas it will be good at idle and no problems will be present until I give it a lot of gas at parking or on the road, It won't accelerate, it feels heavy and it sounds like fuel or air is being interrupted, like if the combustion was not continuous. It gets worst when the AC is on or when I go from Drive to Neutral or Parking or the opposite. It will ONLY gain speed by doing it slowly and continuosly not pressing the gas at its maximum. Distributor cap and rotor, spark plugs and cables, vaccum connections, injectors, fuel pump have been checked, also the alternator voltage and no check engine light is present!.
Any ideas???
PLease help!, thanks a lot
Elder User
Joined: Dec 2004
Posts: 742
Likes: 2
From: Eastern Iowa
Check your timing with a timing gun. If it is okay at an idle,then it is an advancement issue. It truly sounds to me like your timing is not advancing.(correctly) or that your timing is off by quite a bit. That is where I would start.
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
Sounds more to me like a weak fuel pump. A pressure tester is like $30 at Sears or an auto parts store. Spec calls for 55-60 psi at idle for the six.
I had a 1990 F-150 with a six and a weak pump, and it exhibited the exact same behavior.
I had a 1990 F-150 with a six and a weak pump, and it exhibited the exact same behavior.
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Senior User
Joined: Feb 2004
Posts: 236
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From: Guayaquil
Thanks for the comments guys... yes the pump is still there... 
I'll make sure my mechanic is reading the right psi for the pump since you guys think that's what it is... Timing however has been checked and over checked and it is right!...
Do you guys think it might have anything to do with vapor lock in the injectors due to the thermactor injection pipe removal. I posted this before and everyone said I was not going to have any problems...
Thanks for helping guys... don't leave me here!!! keep on posting!
I'll make sure my mechanic is reading the right psi for the pump since you guys think that's what it is... Timing however has been checked and over checked and it is right!...
Do you guys think it might have anything to do with vapor lock in the injectors due to the thermactor injection pipe removal. I posted this before and everyone said I was not going to have any problems...
Thanks for helping guys... don't leave me here!!! keep on posting!
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