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MAF conversion Problem Help a college kid!

Old 03-08-2011, 11:42 PM
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Join Date: Mar 2011
Location: WA
Posts: 4
Unhappy MAF conversion Problem Help a college kid!

Hello everyone. I am in dire need of some information from the mustang crew.
I have a 1990 f250 with a 302 (Ya I know its a truck). I have recently done a mass air flow conversion using the A3M1 computer and MAF out of a 1993 Mustang GT HO. I bought a MAF conversion wiring harness to hook it all up. Roughly for motor specs its a 5.0 with Port and polished heads, Camshaft out of a later explorer (same HO firing order just more for low end torque), Bosch III 19lbs injectors, msd dizzy, wires, and coils. And a K&N Intake. Now for the dillemna. It doesnt want to idle. If I disconnect a vacuum line from the intake plenum, it idles fine right at 750. For obvious reasons this isnt good because air is entering the motor without being read by the MAF. I have checked the computer for codes and it has none. It seems to drive fine, however under load over 3000 rpms it wants to miss. I assume from the vacuum leak? Any ideas? If I plug the vacuum line up I need to hold the throttle open roughly an 1/8 inch or so. If I reset the base idle and the TPS sensor would this be a reasonable cure? Id like to get my motor running properly before i make my trip to WSU at the end of the month for orientation. Thanks for the help!
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Old 03-09-2011, 06:02 AM
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Location: West Virginia
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try base idle reset to start with
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Old 03-14-2011, 01:33 PM
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Join Date: Mar 2011
Location: WA
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Tried the base idle reset and made sure the TPS voltage was in spec and still the same problem. I have another question that may answer this problem. How do you know which MAF sensor you need? When I went to schucks to buy a new one, they offered three different kinds for the same 1993 Mustang HO. I tried one and it gave a code saying voltage was too high so i tried another one and it gave me no codes. However I dont know if that was the right problem.
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Old 03-14-2011, 03:32 PM
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IAC isn't functioning properly its a controlled vac leak. U removed a small line ex: fpr line and it idles fine?
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