Aybody know what causes idle to drop precipitously when my 93RX gets hot & fans come on?

Car idles fine at 850 RPM and runs like a bandit but..after one or two runs down the strip, when it gets hot and the fans are blowing full blast, the car dies at idle & it requires lots of throttle to keep from stalling. After the point where the car cools & fans stop blowing, idle is no problem again so I don't think it's a compression problem.

Is there a solinoid or something that regulates idle when the fans are on high that could be sticking or simply bad?

 

The ISC solenoid is used by the ECU to control idle speed by regulating the amount of extra air flow. When the engine idle load is increased by electric load or the A/C, the ECU is suppose to increase the idle. If this is not happening, then something is hosed!

 

The solenoid is located on the UIM ... opposite the linkage that connects the throttle / cruise control cable. Two 10mm nuts will allow you to remove it (it's a tight fit) and check it out. Basically, air shouldn't pass through it unless you apply 12 volts. There's another solenoid on the UIM (underneath, in the center). Don't worry about this one ... it's only used briefly, when the car is started cold.

 

have you checked your battery?

if it is weak the extra load of the fans will be passed onto the alternator and drag the engine down

eric e

 

Eric I think you have identified the leading suspect. My battery was crappy.

In fact it went dead while I was in the line waiting to race last week. The car sits in the garage a lot lately.

I had the key on to run the fans, something I always to, when the battery gave up the ghost. A real pain in the *** since it was Mustang Day and all I heard were cries of "Shouda bought Ford" as I struggled to get the car out of the way.

I replaced the battery this week & also bought a trickle charger.

However I think I will replace the ISC solinoid just to be sure. 10 years old after all.

Thanks to cewrx7, James & Eric.

 

Let us know if that fixes it.