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Old 01-14-2013, 10:31 PM   #1
86GT40_TireShreader
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Default 86 Mustang GT will not idle

I have an 86 GT that will not idle until it warms up. It had the same problem before I did the mass air conversion. Ive replaced the tps, oxygen sensors, idle air motor, temp sensor, maniforl air temp sensor, all new vaccum lines, egr block off. It has GT40 heads and intakes, trick flow stage 1 cam. I set the timing at 18 deg, bc its high compression, it has good spark new plugs and Ford Racing 8mm wires. Runs perfect and tons of power once its at operating temp. The map sensor is still hooked in the system but the vaccum port is capped like the kit instructed. I dont know if the map sensor could be bad and still effecting it or not. Could it be the wiring? Im out of ideas after that. This thing is driving me nuts, any help at all would be awesome.
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Old 01-15-2013, 12:15 AM   #2
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Have you tried the KOEO - Key On Engine Off Self Test? It may help you pinpoint your problem
http://dfwmustangs.net/forums/showthread.php?t=7908
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Old 01-15-2013, 07:08 PM   #3
Mike T
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Quote:
Originally Posted by 86GT40_TireShreader View Post
I have an 86 GT that will not idle until it warms up. It had the same problem before I did the mass air conversion. Ive replaced the tps, oxygen sensors, idle air motor, temp sensor, maniforl air temp sensor, all new vaccum lines, egr block off. It has GT40 heads and intakes, trick flow stage 1 cam. I set the timing at 18 deg, bc its high compression, it has good spark new plugs and Ford Racing 8mm wires. Runs perfect and tons of power once its at operating temp. The map sensor is still hooked in the system but the vaccum port is capped like the kit instructed. I dont know if the map sensor could be bad and still effecting it or not. Could it be the wiring? Im out of ideas after that. This thing is driving me nuts, any help at all would be awesome.
Do this, the base idle reset...http://www.muscularmustangs.com/idlereset.php
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Old 01-16-2013, 11:26 PM   #4
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I have already done the idle reset and it had no effect. I haven't tried the KOEO test yet. Thanks tho. One thing I forgot about was the car is loading up on fuel bad, running super rich until it reaches operating temp too. Thanks for the input guys. I borrowed a running functional fuel rail with injectors and regulator. A friend told me I may have an injector stuck open may be causing my problem, so thats the next thing Im going to try.
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Old 01-17-2013, 04:07 AM   #5
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Quote:
Originally Posted by 86GT40_TireShreader View Post
I have already done the idle reset and it had no effect. I haven't tried the KOEO test yet. Thanks tho. One thing I forgot about was the car is loading up on fuel bad, running super rich until it reaches operating temp too. Thanks for the input guys. I borrowed a running functional fuel rail with injectors and regulator. A friend told me I may have an injector stuck open may be causing my problem, so thats the next thing Im going to try.
Coolant temp sensor could be the problem.{edit} seen your original post ,you already changed it.

Last edited by Mike T; 01-17-2013 at 04:12 AM.
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Old 01-17-2013, 11:25 PM   #6
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Things to consider after pulling codes and correcting any problems that it shows:

1. Fuel pressure regulator not set correctly.

2. Throttle position senser not set correctly.

3. Mass air meter dirty or not calibrated correctly for the size injectors you have.

4. Salt & pepper connectors at the center of the firewall need cleaned.

5. Vehicle speed sensor not wired properly to new ECU when you converted to mass air.

6. Poor ECU ground.

7. Vacuum leaks.

8. Bad EGR.
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Old 01-30-2013, 09:04 PM   #7
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The great mystery is finally solved!! I got a test light and pulled the codes and that led me in the right direction of which wires to check. Number46 from the ecm goes to the TPS, EGR, MAP, IAT, CTS, and the self test plug, and found that the MAP sensor was left out. I didnt think it would matter since I did a mass air conversion but it does. I skinned the wire and ran it the same sharred lug from the EGR and the SOB fired right up the idle smoothed out and it didnt load up on fuel. Thanks guys for the help.
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