Crazy Ford !
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Crazy Ford !
I have a 1993 F150 5.0 2wd supercab swb. When you start it up it high idles for a little over a minute then it finally subsides to a slower idle. When I back it out of the driveway and pull out it runs perfect shifts perfect for about 1/2 mile. Then the problem starts. First you notice a spark knock not violent but there on acceleration. The transmission will shift quickly from third to overdrive. As you accelerate the truck surges and continues to do so throughout the cruising speeds. its really noticiable aroud 40-45 and 60-65. Im getting really bad gas mileage around 12 hwy. So far Ive replaced the Fuel filter, IAC,plugs, plug wires, distrbutor cap rotor .A friend said it was probably a sticking injector so out came the injectors. they were individually cleaned flow tested by a very reputable injection shop. I reinstalled with new o-rings . At that time I cleaned the throttle body anticeptically clean installed a new tps. The fuel pressure is 40 psi regulator unplugged 29 plugged in to vaccum. Driving me crazy No codes in computer any ideas?
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Joined: Apr 2005
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From: Columbia,S.C.
going by what you've said you have done then as long as all that checks out , check for uneven or low compression pressures, manifold or vacuum leak, as long as the gas and ignition system check out.
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Im aware of that but it shouldnt vary up and down and stay at high idle so long. Thanks for the comment
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Joined: Oct 2004
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From: Wetaskiwin, Alberta
My first reaction to your post was that at 29lbs your fuel pressure seemed a bit low. I thought that the manual called for 40lbs at idle with the regulator all plugged in. I don't know if a 10lb drop would cause all of the problems that you are seeing though - it just struck me as being a bit low. Next up I would consider the possibility of a small vacum leak. Have you had a chance to hook up a vac. guage yet? - What were the results. You might try spritzing the vacum lines with a WD40 or carb cleaner or some such and see if the idle fluctuates - if so you found the leak. There was no fule in the vacum line when you checked the fuel pressure regulator - right?
Just a few thoughts - keep us posted!
Cheers!
Mike
Just a few thoughts - keep us posted!
Cheers!
Mike
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I thought so too. The Haynes manual is all I have to go by its marginal. It says 30-45 running vacuum connected. Its a bit low providing my guage is correct. Ive had it in two independent shops. They tested the rail pressure and ruled it out. I think the Map sensor sounds promising. Ill check it out next . P.S. no fuel in line steady vacuum off tee on intake plenum. Patience and persistence ! l
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