Idle problem when AC on

the-big-e

Registered User
I am having trouble with the idle on a few of my SCs when the AC is on.....

Idle will drop into the 450 rpm range when you pull up to a stop sign or stop light with the AC on and the compressor running......

Sometimes the engines will even stall....

What could be causing this problem.....
 
I think if it were the IAC, it would also affect it with the AC off. Is there a solenoid to increase idle speed when the AC is on or is it programmed into the eec or ircm?

Motor mounts huh? :confused:
 
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I have had 4 (89,90,90,95) SC's do this & to me its common, so I tried another brand of fuel & that did help with the Idle. Good Plugs & wires will help , or if they need replaced the 1st thing I noticed was a lousy Idle in gear. My 95 does it all the time & I am currently on the EGR system for that.
 
How would that cause my idle problem......:confused:
As many SC's as you have... as many years as you've been around.. as many squashed engine mounts as you've replaced... and you haven't run across this yet? :confused:

SuperCoupe owner rule # 3478: routinely check and replace collapsed hydraulic engine mounts. Collapsed mounts, especially on the passenger side, cause metal-on-metal vibration to feedback to the knock sensor. The EEC will retard the timing thus affecting idle speed under engine load. :cool:

SuperCoupe owner rule # 5663: All previously owned Supercoupes need new engine mounts.
 
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I did not know that.....

That makes sense.....

Just goes to show that you can learn something new every day.....:p
 
Check the A/C Compressor

I had a similar problem before and it ended up being the compressor pulley was starting to seize up and robbing power trying to turn it.But you might have checked that already?

Tom
 
I had a compressor pulley sieze up on Black Betty....:eek:

It sounded like she was spinning all of her mains out.....

One of the SCs in question had 2 new motor mounts installed about 2500 miles ago....

And I am pretty sure the other had the PS replaced.......
 
I've got the same problem with my SC as well. When I turn on the AC or Defrost on, I can hear the compressor kick in and the car does not want to idle. It dies on the spot. I'm going to try and replace the IAC. I thought it was the compressor or pressure switch acting up. I'm no AC expert. :mad:
 
Scoff if you wish.. I've pointed it out many times before. Next one who fixes a mount and fixes their idle problem will be about #10 on the list to say "I'll be darned.. he was right!" :rolleyes:
 
So your saying then that IAC's don't get old, plugged up, and lazy so to speak after 15 years or so of running?

Whats easier to replace... motor mounts or IAC?

Frit
 
Its motor mounts... You will be amazed how much bad mounts affect the entire car.They are a bitch to change and I need to do them again on my 89 XR-7...I guess thats OK it will only be the 3rd set in almost 20 years.The IAC is easy to change and they retail for around $100.00.I am SO not looking forward to doing the mounts,my hands are still healing after redoing the entire AC system
 
Mounts are easy to check. Crawl underneath and look up from the back of the engine. If you see/feel 1/8" of an air gap between the Lever arm and the bottom of the bracket, they're fine. Well, not necessarily fine, but OK. If the arm is resting on the bracket, they're collapsed. Mounts degrade gradually. It isn't until you remove them and set side by side with a new one that you can see just how much. Solid rubber mounts last much longer. And, as others have noted, I can't tell the difference as far as smoothness. If the mounts are holding the engine up off the brackets, then they aren't the cause of an idle problem. :)
 
So again I ask, your recommending the person to ignore the IAC and go throug the pain of changing the motor mounts?

You are 100% sure its the motor mounts? and not the IAC?

Again I ask, is it possible the IAC does wear out and can cause a problem, or are you 100% sure its the motor mounts? Are you saying the IAC doesn't wear out and won't cause a problem?

Frit
 
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