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ive got an 86, 5.0, fuel injected, bone stock, automatic, mustang and im runnin rich. It idels rough sometimes (jumps from 500 up to 1000 and back down) but doesnt die and sometimes idles smooth. I know im running rich just by the way my exhaust smells. Also sometimes when im just idleing at a light, the rpm's jump up to around 1200 to 1500 and stay. When i let off the brake the car starts to go by itself, without me hitting the gas, and it will keep going, the rpms wont drop until i turn it off. can somebody please give me an idea about what it could be. i think it could be the automatic choke or an o2 sensor but i dont know how to check them. also it has no mass air flow
 

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88 was the first year for the maf right? does it even have o2 sensors?
 

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We worked on this car this weekend. It has two O2 sensors, one on each exhaust pipe. We pulled the codes and it was setting the ones for rich fuel high fuel pressure, and the idle air solenoid out of spec.

We replaced the fuel pressure regulator, both O2 sensors and the idle air control.

The Idle air code went away but it is still setting the rich fuel codes 42 and 92. I have read several places that this model has a cold start valve. Does anyone know where it is on the fuel rail, or is it connected to a hose off of the fuel rail ? The manual we have does not show it or talk about it that I remember seeing anyway. All of the injectors and the fuel rail are covered by the intake ram air tunnel.

How do you test the temp sensor ? It seems that the car is still running rich on all cyclinders. I need to rule this out also.
 
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