larry_c4

I picked up a '92 lt1 Auto with 68k miles on it recently and I am noticing the idle is lower than other cars that I own. I had the ecm rebuilt because it crashed 2 days after I bought it Now I am noticing that the idle is steady at 500-550 rpm in drive when it is fully warmed up. It stays smooth right at 500 at a stop and does not feel like it is going to stall at traffic lights, it just feels too low(maybe the muffler eliminaters make it sound off, like it's gonna stall). The car also runs about 215°-225° fully warmed up on a 80° day in city traffic with the AC off. So is this idle speed and temp normal for a 92?

Christi@n

Try to remove the IAC and clean it, even clean the TB with TB cleaner

larry_c4

I'm gonna clean the TB. I mean The car has never stalled or stumbled , but sitting at a light when its around 500-50 is a bit scary. You can really hear it drop down because its got eliminators. Maybe its normal and I'm making a big deal out of it?

Tom400CFI

Idle is a bit low, but not hurting anything. Cleaning the TB and IAC is good advice.

Operating temps are normal for the circumstances you described. Fans don't come on until ~230*F.

Christi@n

IMHO muffler eliminator should not modify idle (I think no, wait for some other opinions), once you have cleaned TB and IAC, you can always pull up idle by TB screw.

I've a 1995 manual, ZF. I was on opposite situation than your: high idle, I've tried to do a lot of things without result, clean TB, replacing IAC, try to set TPS, no result. Finally I've pulled it down with screw, its work.

I've readed somewhere, don't remember where, corvette with AT should have idle little bit lower than corvette MT, so mine is about 850-900 your should be 800-850

larry_c4

I tried to get to the Screw but there is a cap that I can't get off. Is there any way to get to that screw?

92ragtop

Don't touch it.

Just do a good TB and IAC cleaning.

Christi@n

Mine was without cap, my only cap is TB gasket, can you post a cap pic?perhaps my pre owner had already mess with my idle screw

Cap is in place in order to not permit to touch screw...

Christi@n

Why no touch? 1/2 turn to raise up idle don't think happen anything,

In case he always can 1/2 turn down

Pa'svette

Does the idle speed change with the A/C off?
Bob

larry_c4

Not really, no idle surges when the AC is on. Im steady at 550rpm.

Pa'svette

Just wondering. The pressure switch on mine went bad and wouldn't send a signal to the ECM to adjust the RPM.
Bob

92ragtop

Not in front of my FSM right now, but IIRC, the throttle position sensor and the IAC work together to set the idle. Messing with a screw that is not intended be be adjusted (hence the cap) is asking for other problems. Find the real reason for the low idle, and then deal with that.
On my 92, I had a number of seemingly unrelated symptoms, including low or high idle. In my case it turned out to be the ECM, and a rebuild fixed all those issues.

larry_c4

I hope it's not the ECM, I Just had it compleatly rebuilt by Cardone they said they used different components so it wouldn't fail.

Christi@n

Mmmm this case, could be a good idea to chech TPS with a multimeter in order to see if it has 0,54 v, as factory specs? If not, than is possible someone else had mess with screw in the past...if instead 0,54 v idle reason is another

larry_c4

The vette has been broken for quite a while. And with the PA winter I didn't drive it much. But now I got it back up and running again with a new opti and injectors. I have cleaned the TB and IAC with cleaner, wiped it down, and it still runs at 550rpm? What now?

Benny42

550 warm in drive is normal. Just drive it, the tach is not exactly a precision instrument in
these cars. If its not stalling or surging at stop lights, don't worry over it.

aklim

Now you get a scanner that can read the ECM and see what the command idle is for the given conditions. Also you can see what the RPM reading is and not what the tach, which is often inaccurate says.

AJT84

Can I ask where you had your ECM rebuilt?

Cliff Harris

I had problems with the engine stalling when I came to a stop. I drove with one foot on the brake and the other on the accelerator so I could catch it and keep the RPMs up. I did a minimum idle adjustment (had to remove the plug) and everything has been fine for the last few years.

I think the linkage bends over time and goes out of adjustment. Plus I see that the idle screw made a slight depression in the throttle linkage tab, which would throw it out of adjustment: