HELLLLLPPPPPP ME LT5 Brothers!!!

[C4Fanatic]

Drove the Z to Eureka Springs, trouble free, hasn't missed a lick. Today on a road tour the car suddenly won't idle down, wants to idle between 1500-2000 rpm. Check everything under the hood we can see, no tools, haven't pulled anything off yet. Throttle cable seems free, I hear the throttle body butterflies clicking shut , so I don't think it's failing to close all the way. Check every vacuum line we can get a hand onto. Try pinching them off to see if any change the idle speed. Nothing...no change.

Just remembered this...car is showing NO SES indication, so apparently no codes.

Tonight I'm walking up to the car from the passenger side and notice something hanging down from the fender area behind the passenger side rear tire and it appears to be trapped between the body work and the tail pipe. Reach down to grab it and find some kind of vacuum canister I believe.

Question...IS this indeed a vacuum canister that is mounted back there? Could it have come out of its mount and dropped resulting in a disconnected vacuum line? And could it possibly be causing my issue?
Any other ideas as to what may be causing my high idle speed?
I'm going to guess that to get at it, I'll have to remove the rear tire and inner fender to see it back there.

I'm headed to the tech section sticky of "Been there, Done that's" but thought I would throw this out to the experts in the mean time.

Thanks for any help in advance guys.

David

[A26B]

David,

On the passenger side of the engine, just in front of the rear pair of plenum runners, is a black plastic tube abt 1/4" dia, coming from under the plenum. Unplug the line at the connection there and put you finger over the open end of the plastic tube.

I think it's the vacuum source for the charcoal cannister that is located behind the RR wheel. If putting your finger over the now open end of the black plastic pipe restores the idle, just cap or plug the plastic pipe until you can get home to fix the cannister & loose vacuum piping or whatever is causing the vacuum leak.

[C4Fanatic]

I'll check that first thing in the morning. Thanks Jerry!

I also need to double check how the vacuum pump is acting. I read in one of the tech threads that with key on, engine off it should run for approx. 5 secs or so as it builds vacuum in the system, then shut off and stay off. If I read correctly, if it keeps cycling on and off, I am for sure to have a loss of vacuum somewhere...makes sense even to a bonehead like me...so I have a coupe directions to go.

Other than the high idle the car is running fine on the road, just make loping around town a bit of a challenge to say the least!

[gbmidyear66]

I have a similar issue, my engine has suddenly decided it wants to hang, at about the same RPM as yours. After many hours of chasing the problem, I'm convinced mine is the throttle body. One thing you might want to do is to place a STIFF book over the airhorn, see if that stalls the engine - if it does - your issue is likely not a vacuum leak (TPS, IAC, Throttle body would be next places to check).

Good luck, and let us know what you find

Glenn

[LGAFF]

IAC? Reset procedure is to start the car with pedal 3/4 depressed and then immediately turn the car off, then restart. Worth a shot

[Ccmano]

Originally Posted by C4Fanatic

Tonight I'm walking up to the car from the passenger side and notice something hanging down from the fender area behind the passenger side rear tire and it appears to be trapped between the body work and the tail pipe. Reach down to grab it and find some kind of vacuum canister I believe.
David

I'm betting on a vacuum leak...


H

[C4Fanatic]

Well guys it's still not solved. Thought we had found it this morning at the car show, we found that the MAP sensor hose was indeed off...strange as it wasn't throwing a code, no SES light. Even had Gordon Killebrew climb all over the car with me today. Replaced the MAP hose and it still wants to idle between 1500 and 2000rpm. Checked every hose we could get a hand on, no luck. Disconnected power to see if we had any codes that needed cleared, still no luck. Gordon says it's acting like a vacuum leak, but we didn't find anything. Going to check a few things when I get it home, if I have time, have to fly to Vegas Monday for a week, then when I get home, it's off to Texas. I had planned to take it to Texas and go to the gathering at Cory's, but I'm just not sure right now. It runs fine on the road, so who knows, I'm still up in the air on that. Maybe someone down there will find something I've overlooked between now and then. I am going to try the IAC reset that LGAFF suggested in the morning. It's bed time.

Thanks again for all the input guys, I'll keep digging, but tomorrow it just has to get me and mama home.

[Paul Workman]

It'll be something silly, like the time a little sliver of that rubber seal they put on those circular air filters (4-bbl carburetor) somehow came off and wedged the secondary throttle plate open just a weee bit. Suddenly my idle was around 3000 rpm...SAY WHAT???

Well, I'm intrigued. Do let us know what you find!

P.

[gbrtng]

I had a charcoal canister fail - it's in the right rear fender - so you might try replacing it and check the two vacuum lines to the engine compartment very carefully.

[C4Fanatic]

I was able to climb under it yesterday and slip the canister back into the bracket it rides in and also re-attach the plastic cover that keeps debris out of that area. Both lines were on the canister and it looked fine, but I'll probably give it a closer look now that the car is home and in the garage.
Made it home with no issues today, she runs fine down the highway, but just doesn't seem quite right as far as a "seat of the pants" assessment goes, I'm sure most of you have been in that situation with your cars. She just ain't quite right.
Oh well, I'll find it, fix and be good to go again soon.