MAF conversion Problem Help a college kid!
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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. 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!
I have a 1990 f250 with a 302. 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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Joined: Jun 2006
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From: Ottawa, Ontario
OK more info needed. What have you done with the stock truck wiring? Is the conversion harness an overlay or does it completely replace the stock harness? Is the MAP sensor still connected to manifold vacuum?
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Yes I did just use the overlay harness. The Map Sensor is disconnected from the vacuum like its supposed too. Id like to add another piece of information that when sitting at a stop light at idle it idles 'ok' then after 20-30 seconds it wants to start surging and want to die.
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