Need some help with my 302. Out of a 93 Mustang. The wiring in the truck was terrible since I got it, so I pulled an engine harness out of a 91 mustang last week. I spent two days wiring it up. Main wiring to do was EEC Relay, Fuel Pump Relay, and Neutral Safety Switch. So i get the harness in the truck, turn the key and it fires right up. Now comes the issue. The engine will not rev over about 3500 RPM. When the tach hits between 3500 and 4000 it bogs down hard, will not rev any higher.
Also once the truck warms up to temp, it idles from 1600 to 2000 RPM. It did this with the old harness and the new one.
I have two different PCM's and I have both these problems with both computers.
I have a feeling this might have something to do with the EGR valve but haven't found much help online.
Any suggestions? I'm running out of leads to follow to check that would cause this.
Last edited by My91Ranger; 01-04-2009 at 11:47 AM.
Timing just reset with the SPOUT Disconnected, set at 10*. Fuel pressure regulator is about 6 months old. I'm using both a A9L and an A9P. Its a t5 manual.
The IAC has been throughly cleaned, but when it is disconnected the idle does not change. Very odd, typically the idle drops when disconnected. I doubt there are any major vacuum leaks b/c it is pulling 20 PSI of vacuum at idle. The idle set screw is set as low as possible without the throttle vane sticking. This was adjusted off of the truck. The TPS is only a few weeks old and is set at .99 Volts at idle.
When first started and engine is cold, before the idle is absurd, and its sitting around 1100, disconnecting the IAC does have an effect. I have 3 I can try thanks to the junkyard and carb cleaner. I tried pulling the vacuum line off of the EGR when the idle was hanging and it had no affect, and the vacuum line seemed to have no vacuum, at least anything I could feel. I think something might be up with the EGR vacuum regulator solenoid. I think in the morning I will check that and pull the EGR off the intake so I can give it a good cleaning and check the plunger.
Well I have everything working now. The reason the truck wouldn't rev past 3500 was I had one wired connected incorrectly on the TFI Module on the Distributor so it was limiting the ignition. I also pulled off the EGR valve and cleaned it really good. Was pretty bad, alot of carbon build up. I rewired the EGR Vacuum regulator solenoid, and pulled the IAC off, checked to make sure it wasn't clogged and reinstalled it. So far that took care of everything. The truck is idling nicely at 900 RPMS like its supposed to.
The wiring harness was a royal pain but was worth it. The truck runs alot smoother, it doesn't shake, AND the best part is the engine mis is gone. I have a feeling the injectors wiring was bad and caused the mis. Truck feels much smoother and quick.