300 efi idle HELP
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Joined: Apr 2006
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300 efi idle HELP
87 F150 300 efi
Went to start it this morning, idle is awful like it is running on only a couple of cyliders and just barely running, if i give it throttle it smooths out but as soon as i am off the throttle it is barley running? Smells gassy and some black smoke puffing from exhaust...help i need this for work tomorrow ran perfect when i parked it last but has been sitting for about a week and the temperature here has plummeted but i don't know if that relative Thanks in advance
Went to start it this morning, idle is awful like it is running on only a couple of cyliders and just barely running, if i give it throttle it smooths out but as soon as i am off the throttle it is barley running? Smells gassy and some black smoke puffing from exhaust...help i need this for work tomorrow ran perfect when i parked it last but has been sitting for about a week and the temperature here has plummeted but i don't know if that relative Thanks in advance
Posting Guru
Joined: Sep 2004
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see if the codes lead you in any particular direction, just bear in mind, just because you get a code for a specific sensor, thats no indication of a bad sensor, just more information to whats happening or not happening
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Joined: Jul 2005
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Rough Idle, Gassy Smell Bad News
Hello 6T6Shorty,
What you describe is just one of the problems my '89 originally had. The main problem was the seals on number 5 & 6 fuel injectors were shot, allowing a mist of fuel to escape when those two injectors were charged. It was extremely difficult to see under the rails and other parts, and it didn't produce a wet fuel area, but you could smell it and if you looked under the obstructions you could see the mist at idle. I phoned for new injectors and that cured the problem.
BTW, it's difficult to buy a new set of injectors that are matched, but there is a guy back east (Ohio? can't remember, his phone number is out in my motor-manual) who rebuilds and *matches* injectors, and will send a set directly to you.
So check carefully, and see if you can't find some fuel mist under the injector cooling tube down by the injector bases.
Good luck!
What you describe is just one of the problems my '89 originally had. The main problem was the seals on number 5 & 6 fuel injectors were shot, allowing a mist of fuel to escape when those two injectors were charged. It was extremely difficult to see under the rails and other parts, and it didn't produce a wet fuel area, but you could smell it and if you looked under the obstructions you could see the mist at idle. I phoned for new injectors and that cured the problem.
BTW, it's difficult to buy a new set of injectors that are matched, but there is a guy back east (Ohio? can't remember, his phone number is out in my motor-manual) who rebuilds and *matches* injectors, and will send a set directly to you.
So check carefully, and see if you can't find some fuel mist under the injector cooling tube down by the injector bases.
Good luck!
Senior User
Joined: Dec 2006
Posts: 164
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From: Gray, TN
You may have a bad fuel pressure regulator. (the round thing on the fuel rail with the vacuum line on the top) Its supposed to let the right amount of fuel back out the return line to keep the pressure where it should be. Hook a fuel pressure gage up to the schrader valve on the fuel rail. It should have about 35-40 psi at idle. I worked on a '95 f150 w/ 302 that was barely running and blowing black smoke. It had a bad fuel pressure regulator and was running at 90 psi, just drowning it in gas! If there is gas leaking out of the regulator into the vacuum line that would also indicate a bad regulator.
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