Rough Running
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New User
Joined: Apr 2004
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Rough Running
I have a 94 F-150, 5.0L engine with 117,000 miles.
Recently the truck has been running very rough just driving down the road so much so that the rearview mirror shakes so bad you can not see anything but a blur. The vibration is the worst when accelerating lightly or just maintaining a steady speed. When I put my foot to the floor the vibration does not seem to be a problem and the truck does not seem to be lacking any power, but as soon as I let off the gas the roughness returns. Also when I brake hard to a full stop I can feel the engine surging untill I come to a complete stop or release the brake and coast.
I have replaced the plugs, plugwires, cap, rotor, fuel filter. I checked the fuel pressure "40 psi", checked the fuel pressure regulator, checked the EGR valve, checked the TPS and looked for obvious vaccum leaks so far no luck.
Where do I go from here?
Recently the truck has been running very rough just driving down the road so much so that the rearview mirror shakes so bad you can not see anything but a blur. The vibration is the worst when accelerating lightly or just maintaining a steady speed. When I put my foot to the floor the vibration does not seem to be a problem and the truck does not seem to be lacking any power, but as soon as I let off the gas the roughness returns. Also when I brake hard to a full stop I can feel the engine surging untill I come to a complete stop or release the brake and coast.
I have replaced the plugs, plugwires, cap, rotor, fuel filter. I checked the fuel pressure "40 psi", checked the fuel pressure regulator, checked the EGR valve, checked the TPS and looked for obvious vaccum leaks so far no luck.
Where do I go from here?
Senior User
Joined: Dec 2003
Posts: 354
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From: Memphis, TN USA
What kind of ignition system do you have?
If your ignition system uses a crankshaft position sensor, check its wirings to make sure it is not rubbing off the engine block.
Check each spark plug wires for any nicks and probably rubbing off the engine block or cross-firing. Make sure the spark plug wire boot are fully seated in the spark plugs as well as on the distributor cap.
If your ignition system uses a crankshaft position sensor, check its wirings to make sure it is not rubbing off the engine block.
Check each spark plug wires for any nicks and probably rubbing off the engine block or cross-firing. Make sure the spark plug wire boot are fully seated in the spark plugs as well as on the distributor cap.
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Joined: Aug 2003
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Does the truck vibrate when you are sitting still with the engine speeding at a steady speed? From your description it would be a guess to say whether it is a rough engine or a tire out of balance or anything else.
The full throttle thing could be a clue. Full throttle the weight shifts and the computer runs in a different mode (WOT), without reading the sensors.
Does your check-engine-light work? Do you have any error codes?
The full throttle thing could be a clue. Full throttle the weight shifts and the computer runs in a different mode (WOT), without reading the sensors.
Does your check-engine-light work? Do you have any error codes?
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Joined: Apr 2004
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I checked the trucks records and saw that the o2 sensor had never been changed and I thought it would not hurt, unfortunately it did not help either.
The truck runs smooth if I push it into neutral and coast so I feel good about the tires running smooth. The ignition componets are all new except the coil.
The truck runs smooth if I push it into neutral and coast so I feel good about the tires running smooth. The ignition componets are all new except the coil.
Senior User
Joined: Mar 2003
Posts: 306
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From: Mobile, ALABAMA
I would have it checked out on a computer....I dont know if they have one where ur from but in Alabama, theres a place called Max Automotive, they do diogonstics for free....you might want to check into that, maybe see if anyone else does it in your area....couldnt hurt....
