EFI 300 advice needed
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Elder User
Joined: Oct 2007
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EFI 300 advice needed
My '91 300EFI has a bad stumbling problem except when you hammer it; and at idle (only in park) the RPMS drop to the point it almost stalls, then shoots up. You put her in drive, it doesnt do that.
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
Elder User
Joined: Jun 2010
Posts: 509
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From: Casper, Wyoming
My '91 300EFI has a bad stumbling problem except when you hammer it; and at idle (only in park) the RPMS drop to the point it almost stalls, then shoots up. You put her in drive, it doesnt do that.
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
I agree with AB, though. sounds a lot like a vacuum leak. check the intake manifold gasket and every place air can get into the intake.
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Elder User
Joined: Oct 2007
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If the folks at the parts store are agreeable, try a wiggle test. Plug in the scanner and follow the instructions for the test. Wiggling the wires on the sensors can sometimes reveal a bad connector.
I agree with AB, though. sounds a lot like a vacuum leak. check the intake manifold gasket and every place air can get into the intake.
I agree with AB, though. sounds a lot like a vacuum leak. check the intake manifold gasket and every place air can get into the intake.
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Joined: Apr 2008
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Have you tried disconnecting the battery overnight? sometimes the computer gets scrambled and it will reset when it's disconnected.
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Trailering
Joined: Nov 2010
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My '91 300EFI has a bad stumbling problem except when you hammer it; and at idle (only in park) the RPMS drop to the point it almost stalls, then shoots up. You put her in drive, it doesnt do that.
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
I have new fuel filter, put on a TPS (throttle positioning sensor) and a new MAP sensor. They plugged my van in at the auto parts store cant get a fault reading.
Any ideas ?
you can run your own diag test that will flash out engine check light codes look it up here how to do this wait here is the link to the thread
How-To: retrieve trouble codes- OBDI - Ford F150 Forum - Community of Ford Truck Fans
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Elder User
Joined: Oct 2007
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It seemed to run better but at idle it still fluctuates and stumbles when accelerating (though it seems to be doing better)
Any other ideas ? I really like this old van, but its pushing my patience
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Elder User
Joined: Oct 2007
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And I thank you all for your advice
Trailering
Joined: Nov 2010
Posts: 20
Likes: 1
pour 4 OZ of acetone /nail polish remover in the tank believe me it works makes the injectors like new in one tank i saw noticable performance in about 50 miles of driving
try a clifford 270 cam ...i have owned four f150s all with the 4.9 -6 and the one i just bought is the only one that does not stumble in the low end has this cam ....cam it.... if you read most all EFI f 150s have this problem ...the fuel mixture in the low end rpms it to rich the clifford cam corrects this other cams may also
try a clifford 270 cam ...i have owned four f150s all with the 4.9 -6 and the one i just bought is the only one that does not stumble in the low end has this cam ....cam it.... if you read most all EFI f 150s have this problem ...the fuel mixture in the low end rpms it to rich the clifford cam corrects this other cams may also
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Joined: May 2009
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From: Eastern Ky
Ok guys, here's a new one: my 94 stumbles and stalls until it finally dies unless you either give it fuel or put the transmission in P or N to let the engine s' rpms raise back up.....the kicker? It only does this occasionally when I stop at say, a stop sign, red light, etc.....And now it's developed into doing it every time I put it into reverse....Any info is appreciated