Idle Speed

[Memphis]

So, I now have a working A/C in my '94 with 2.3/5spd. When I trust the truck to drive it, anyway. It seems to me that turning on the A/C should increase the engine idle? Sitting still in a parking lot I can hardly turn the steering wheel unless I give it more gas. Is there a way to adjust the idle or is this normal? Thanks,Scott

 

[Hawk1339]

The Powertrain Control Module has an input that tells it when the AC is turned on. It should be controlling the idle speed. You could have a bad connection preventing that signal from reaching the PCM.

 

[v8318cid]

Weak engine maybe? Anyway, if the PCM acknowledges the A/C is capable of running based upon the pressure switch status, it should adjust the idle to compensate for the load when the A/C is selected. If the A/C pressure switch is bypassed for some reason, this would prevent the PCM from making the necessary adjustments since it would not have received the signal indicating that the A/C is safe to run (aka within the correct pressure range). Either way, the 2.3 litre is only rated at about 100hp in that year range and this assumes it is in optimal condition. The A/C adds a significant load to the engine (3-4 hp approximately) and can have a negative impact on the performance of an already strained/weak engine.

 

[Earl43P]

Clean or replace the IAC, it controls idle.

The 4 cyl models of this era also have a Power Steering Pressure Switch (its wire colors should be Y/LG and GY/R). WHen the PS press switch senses low pressure, the PCM should bump up the idle to compensate. When the A/C is selected on and the compressor clutch is engaged, the PCM should bump up the idle to compensate for that load too.

Both of those scenarios indicate that the IAC isn't functioning properly. Remove the IAC (2 8mm bolts) and clean it with a solvent. Remove the crud from its shaft with a brush.

An easy test for the IAC is turn on the AC. Each time the compressor clutch is engaged, the idle should increase. Remove the electrical connector from the AIC and see if any change in operation occurs. There should be a marked difference with the connector off. It may even stall when the compressor clutch engages or power steering is turned hard. If you don't get that result, your IAC may be inoperative. Try cleaning it before replacing it.

 

[kimcrwbr1]

Also take a small brush with some fuel and open the throttle plate and clean the throttle body and plate. If you pull the throttle body make sure you get new gaskets first to put it back together with.

 

[killj0y]

i second cleaning the IAC...