Running/Idle problems
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Joined: Feb 2012
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From: Houston
Running/Idle problems
I have an 86 f150 4.9. I left it at airport parking and it was running great. I came back a couple of days later and started the truck and it ran completely different.
Now I run the engine, idles smooth until about 10 sec later. starts sucking lots of air from the carb, almost dies, levels back out and repeats. Eventually the idle does smooth out and this happens less. Now when I put the truck into gear the rpms shoot up for a second and the truck jerks forward or reverse, after the rpms drop for a second and it no longer jerks. This repeats non stop.
The only time the truck drives normal is when I'm doing above 15 mph. anything lower than that I have to have one foot on the gas, and one on the brake to give it the extra throttle it needs.
I rebuilt the carb, checked vacuum lines for leaks, and replaced the fuel filter and still have the same condition. Any one seen this before?
Thanks
Now I run the engine, idles smooth until about 10 sec later. starts sucking lots of air from the carb, almost dies, levels back out and repeats. Eventually the idle does smooth out and this happens less. Now when I put the truck into gear the rpms shoot up for a second and the truck jerks forward or reverse, after the rpms drop for a second and it no longer jerks. This repeats non stop.
The only time the truck drives normal is when I'm doing above 15 mph. anything lower than that I have to have one foot on the gas, and one on the brake to give it the extra throttle it needs.
I rebuilt the carb, checked vacuum lines for leaks, and replaced the fuel filter and still have the same condition. Any one seen this before?
Thanks
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From: Houston
ah, forgot to mention, about 5 years ago I took the truck to a mechanic who replaced the carb with one that was older and not computer controlled. Ran great for several years and started having problems with the vacuum lines. Was replacing those when I noticed that the carb was not the same as what it should be.
I want to bring the truck back to original condition, the carb is the only thing that isnt the same.
Regardless, not possible to pull codes for the carb.
I want to bring the truck back to original condition, the carb is the only thing that isnt the same.
Regardless, not possible to pull codes for the carb.
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Joined: Nov 2007
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From: Denver Metro Area, CO
Hmmm... forgot to mention critical details like that....
If you replaced the computer-controlled carburetor but not the computer-controlled distributor, then the computer has most likely locked your ignition timing at something around 10° BTDC. it would run that way but performance will be sub-optimal (but which doesn't explain your symptoms).
If you replaced the computer-controlled carburetor but not the computer-controlled distributor, then the computer has most likely locked your ignition timing at something around 10° BTDC. it would run that way but performance will be sub-optimal (but which doesn't explain your symptoms).
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From: Houston
cluster or wires actually. Ran like a champ for years after that shop made repairs. I'm starting to think that something has gone wrong inside the carb. I rebuilt it 4 months ago and it was running great. Maybe I did something wrong. I'll pull it apart next week and check to see if anything is amiss. Whenever I get project money put back up I'll do my engine rebuild and put everything back to stock. I've got a garage to work in for the first time ever.
Just need it to work for when i have to drive to the airport till december...but we'll see what happens
Just need it to work for when i have to drive to the airport till december...but we'll see what happens
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