Won't Idle
 

I have a 92 LX street/strip mustang that I've been building. I assembled a 347 for it and after finally being able to start it up I found that it won't idle and is running very rich. It will run as long as it does not fall below 2000 RPM.

The motor has a Pro-M 80mm mass air meter calibrated for the 42# Bosch injectors I'm using. 70mm throttle body, Holley Systemax intakes, PCV is not used (blocked at intake), EGR is still hooked up but not being used, using air temp sensor and water temp sensor in lower intake, using Bosch O2 sensors, throttle position sensor at .985 Volts, using stock computer.

I plan on installing a supercharger eventually so I went with larger injectors than I currently need. All sensors are new.

I've been talking with Pro-M and have even sent the meter back to adjust the calibration but we haven't been able to solve the problem yet.

Please respond with any questions or recommendations.

Thank you,
J.T. Munk

JT, I feel your pain...my LX also has idle issues. I installed the air adjuster from Windsor-Fox. That helped a little.

On TP settings, I've set the voltage a little lower to fool the EECIV into giving less fuel. I believe this helps as long as you can get the necessary voltage for WOT...to that end, I use the Casper Electronics TP device which delivers full voltage to the EEC at 70% throttle range.

Another idea is an adjustable fpr. Some are adjustable for "gain" so you can turn down the fuel pressure when at idle, yet still get 38-40 psi at zero vacuum (basically during WOT). If you reduce fp at idle, you will reduce the fuel to the motor. I've done that also, and it's helped some.

Another idea (which also helps) is to rotate the MAF within it's hoses. Just loosen it, and rotate it 10-20 degrees toward the fender. Generally, when the sensor is rotated closer to fender, the MAF will receive a weaker air flow signal. When the MAF is rotated so the sensor is closer to the engine, the MAF will send a stronger air flow signal. Make sense?

There you have it, that's all I know.

Good luck!

Re: Won't Idle
 

JT,

Any other symptoms? A miss or backfire, bucking and stalling. Didn't see if you had actually driven it yet. Ensure you don't have a vacuum leak. I just spent a BUNCH of time tracking one down, and had similar symptoms. Unfortunately, mine was the lower intake gasket, so off it all came again. Once I got mine to pull 12inches at idle, the woes went away. Good Luck, let us know what you find.

joex