Air conditioner kills engine. Any ideas?
 

I have a 1995 Nissan Sunny (Sentra to those not in Japan). When I turn on the A/C, the engine dies. If I turn it off and start it again, it runs a bit rough at first, then everything is normal. Until I try the A/C again. I can push the button for the air if the fan is off, and there is no problem. It only happens when the fan is on. If I rev the engine while I do this, it will stay on until I let up the gas. If the A/C button is off, the fan works fine (defog, etc.).

I knew about this when I bought the car. The guy I bought it from had taken it to the Nissan dealer here, and they told him it was probably the fuel injectors- either the seals or the injectors themselves were cracked.

It seems to me that if the fuel system was involved, it would be a more constant problem regardless of the A/C. It sounds to me like a vacuum leak somewhere that is only present when the A/C is actually trying to pump.

It's a '95, 1.5 liter, manual trans, 110,000 km (about 65k miles?) on the clock. After I bought it I had to get the inspection where they check everything, had all the filters replaced (including the A/C filter). There were no problems with the basics systems, no oil or fuel leaks, good spark, etc. It gets about 10k/liter (25mpg) in town.

Any ideas? I'm about to take it in to get it fixed before the truly brutal part of the Japanese summer hits.

could be what you think. Could also be that the idle is not being increased when the AC is turned on. Does it die when you're driving and you hit the AC, or just when you're idling?

If I'm driving and hit it, it's ok, as long as the revs are up. For example, in the freeway, no problem. In town, as soon as I put in the clutch and take off the gas to downshift for a turn or a light, it dies. Would the idle increase be part of the computer? I'm not that familiar with A/C, how does the idle get boosted?

Idle is controlled by the idle air control valve. There's a list of how different ones work here. If it's vacuum controlled you should check that line or if it's electric, check the wiring. It might be possible to clean it to restore function or it might have to be replaced as well. It's possible to troubleshoot and check that is the problem, procedure varies on the type.

Thanks for the link, fiatguy! I'll check that out, and give it a cleaning. If anyone else has an idea, I'm all ears. Thanx in advance...

I posted my problem on a Nissan repair forum, and someone said it's the a/c clutch as the clutch doesn't engage until the fan turns on. I don't know... the a/c blows cold air when it's on. If the a/c clutch was seized, would it still blow cold air? Would that affect the idle?

Could be the clutch but that doesn't sound quite right to me.
Yes if the clutch was seized it would blow cold air. And yes it COULD affect the idle but the idle control should still boost the idle with a seized clutch at least when you first turn the A/C on I'm thinking.
Just how high do the revs have to be so you don't stall out?

AC is a huge draw on the engine, and accounts for decreased MPG as well as poor performance.

I had a car where you turned on the AC while it was in gear, it would start to roll backwards because it didn't have enough power to keep it in place. :)

I don't have a tach in the car, but I would guess it's around 3000 going by ear. Everything seem to work fine if I'm on the freeway with steady RPMs and no stoplights. I really appreciate your thoughts everyone. I didn't see how it could be the fuel injectors and you've pointed me in what seem like a much more realistic direction.

I took the car to the shop today, and they are replacing the idle air control valve. Thanks for the tip!

In the end, they cleaned the IACV. They also charged the a/c gas, and replaced the battery. Total cost $100. Car runs like a champ with icy a/c. I love my mechanic!

Excellent, hope it keeps running long and well!