AC causing a hanging idle

[e30kawi]

Seems like an odd problem, but whenever I turn my air conditioner my rpm's hang where they were cruising at. Say I am cruising along at 3000 rpm's and shift and it stays right there. Any ideas on a fix for this?

[ELVA164]

Wait, what? Do you drive a manual or an automatic? It really shouldn't matter, because if you shift gears it's impossible for the engine to remain at 3000rpm (for example) in both gears. Do you just mean the tachometer stops working when you turn the A/C on? If so, common issues include the solders on the gauge cluster itself and/or the SI batteries in the gauge cluster.

[e30kawi]

Wait, what? Do you drive a manual or an automatic? It really shouldn't matter, because if you shift gears it's impossible for the engine to remain at 3000rpm (for example) in both gears. Do you just mean the tachometer stops working when you turn the A/C on? If so, common issues include the solders on the gauge cluster itself and/or the SI batteries in the gauge cluster.

Its a manual. Say I am coming up to a stop sign and push in the clutch at 3k, the revs hang there until I let the clutch back out at what would be a lower rpm, like pulling away from a stop. If I am cruising along at 3k and let off the gas pedal the the car kinda acts like the cruise is on, it will coast down but not as fast as it would if the ac weren't on.

[e30kawi]

bump. Anyone?

[ELVA164]

I'm definitely a bit stumped. It sounds like a sticking throttle cable at first, but the a/c thing throws a wrench into that. It's almost like the wiring for the a/c has somehow crossed into wiring from the ECU that controls idle or the wiring for the TPS or something...have you dug into the wiring under the gauges or around the ECU? Is anything sketchy-looking?

Aaaactually, it's almost like the cruise control is being activated when you turn on the a/c. Can you cause it to stop by touching the throttle and/or brake or with the cruise control stalk?

[e30kawi]

have you dug into the wiring under the gauges or around the ECU? Is anything sketchy-looking?

Aaaactually, it's almost like the cruise control is being activated when you turn on the a/c. Can you cause it to stop by touching the throttle and/or brake or with the cruise control stalk?

I have not "dug" into the wiring, but I have seen it, it looks to be stock and unmolested.

The revs hang whether I hit the brakes or push in the clutch. The only way to get them down is to turn off the AC or to lug the motor in a high gear. It seems super weird but I know I can't be the only one who has had this happen.

[mojo_monkey]

My 1990 5spd kind of did this too when the charge was low. I have not converted my AC system at all, so it's still r12. I found a guy that still had some r12 and he dumped in a little over 1lb if I recall correctly. Once I had more refrigerant the car behaved much better with the AC on.

My car was doing stuff similar to what you describe. It seemed that if the AC was on it was almost like having cruise control on. Specifically, if I lifted off while driving down the freeway, the car would barely decelerate.

[jlevie]

When AC is engaged the DME (or ICM on an ETA) will raise idle to compensate for the additional load. But nowhere near as much as you are seeing. My suspicion would be a problem in the ICV probably aggravated by intakes and perhaps a bit of binding in the throttle body or cable.

[CW325]

Weird I had the same problem but it was happening without the AC on. I haven't noticed it lately but if it act up I'll try swapping my ICV and see what happens.

[AlphaE]

When AC is engaged the DME (or ICM on an ETA) will raise idle to compensate for the additional load. But nowhere near as much as you are seeing. My suspicion would be a problem in the ICV probably aggravated by intakes and perhaps a bit of binding in the throttle body or cable.

^^^ this.. if its stuck at 3k and you turn off the ac do the rpms drop down?? thats the load circuit.. could be DME related or hopefully the ICV as stated above.. either way check the ICV 1st. its easy and cheaper than a DME.