Mass Air Question....

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Apr 25, 2008 | 07:12 AM

bob1987f

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Mass Air Question....

hello, my 87 f150 with a 5.0 and the ford racing mass air conversion is acting up on me. i was driving the other day and at low rpms under a load i heard a backfiring (popping) noise from the engine.

well i didnt drive it for a couple days and yesterday i started it, and it was idleing rough and bogging and backfiring when i gave it some throttle.

while it was idleing i unplugged the maf and there was absolutely no change in how it ran. so common sense says that my maf is bad.......well i just so happened to have a 70mm motorcraft maf that i just bought to upgrade from my stock 55mm that comes with the maf conversion, so i just went ahead and swapped them......and same thing! so ive deduced that my maf is not getting a signal from the harness. ive checked my wiring and there is nothing wrong with it, nor has it moved or been touched by anything else.

could my computer be going bad and not sending a signal to my maf? thats all i can think of.....thanks

Apr 25, 2008 | 07:28 AM

bluesman2333

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The MAF is one of several sensors that control fuel. Why not start by eliminating the more common tuneup items that might cause drivability problems? Plugs, wires, cap, rotor, vac lines, fuel pressure including checking the vac line going to the FPR making sure that there is no fuel in it, plugged cats, etc...

Apr 29, 2008 | 04:03 PM

EPNCSU2006

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From: Concord, NC

Have you actually checked the MAF with a voltmeter to see what the actual output signal is? Simply unplugging and swapping a part you think is the problem won't get you very far on EFI. Are there any codes stored in the computer?

Apr 29, 2008 | 06:38 PM

Kemicalburns

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From: Bend,OR

gotta check codes before throwing parts at it. whats yoru fuel pressure at?

Apr 30, 2008 | 03:41 PM

bob1987f

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ok....yesterday i probed the maf on my 95 bronco with a 5.0. ground to power wire was like 13.5v. ground to each of the sensor (middle) wires was right at 1v at idle.

went to the 87, ground to power was 13v, ground to middle wires was nothing......when i put the 55mm maf on it, it definately runs better, but if i rip the throttle open real fast from idle it will still backfire here and there

when i do it with the 70mm maf its worse.....all my ignition is new, my timing is at 12 degrees btdc with the spout connector removed, and i also sprayed tb cleaner all around with it idleing yesterday and didnt notice any vaccuum leaks.

also i didnt change anything and then this happened, its ran great for like a month straight after i went through the motor, and it just developed this problem all the sudden.....thanks

Apr 30, 2008 | 04:12 PM

EPNCSU2006

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From: Concord, NC

Any trouble codes stored in the computer? I found these links through a google search. Maybe they will be of some help: http://www.allfordmustangs.com/forum...as-tests-1.jpg
http://www.allfordmustangs.com/forum...as-tests-2.jpg

Apr 30, 2008 | 04:53 PM

bob1987f

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thanks those help alot! if anyones noticed the haynes manual for the 80-96 f150 and bronco dont even mention the word mass air flow sensor in the whole book!

i need to retrieve any codes....will do this tomorrow (thurs) and report back. thanks