Higher rev when at stop light or stop.

[joe912/62]

Having an issue recently with the rpm's going higher when at a stop light. If I step on the clutch and advance forward for a few feet the idle goes back down to 950+-.
Could it be a slipping clutch or something to do with the CIS?
Any help would be appreciated.
Joe

[Rodsrsr]

Sounds like your throttle rod is getting hung up. Possibly the bushings in the tunnel are shot, but the rod is rubbing against the clutch cable which is why the idle drops down when you press in the clutch.

[rwest]

I’ll add that you can do a quick test of this by pulling back the throttle pedal with the edge of your foot or hand- if you can do it safely to see if the idle drops.

[joe912/62]

I'll try these suggestions, but when I release the clutch to creep forward I'm not applying any Throttle on the pedal and the idle sets back down to normal.

[jac1976]

Originally Posted by joe912/62

I'll try these suggestions, but when I release the clutch to creep forward I'm not applying any Throttle on the pedal and the idle sets back down to normal.

By “release the clutch,” do you mean taking your foot off the pedal? Not being pedantic, but that is engaging clutch. And I would think this normal as you’re now loading motor.

[proporsche]

check you distributor advance plate, if it is not frozen..
Ivan

[joe912/62]

This is a 82SC and yes and slowly take my foot off the clutch pedal to creep forward.

[B_El]

I had the exactly same problem after the manifolds were rebuilt and Permatune added. My mechanic suggested issues with the distributor and sent it to Jerry Woods Enterprises in Campbell, CA for rebuild and "recurving". The recurving is to set the dizzy to work better with modern fuels (?). Well... the increased rpms at idle are gone and my car has never run better in the 22 years I've had it. The difference is night vs day. Cost was ~$800 2 years ago.

[EC900]

I recall you had some issue a while back with the throttle linkage “ticking” near the engine which is normal.

But did you ever remove your floorboard and examine the pedal cluster and related bushings? The one to inspect is the two nylon bushings on the bell crank lever.

The linkage can be binding, may just need lube - But if you manipulate the clutch pedal it will affect the throttle cable inside the tunnel as there’s are three bushing in there too that break causing cables to slop around and bind. Depressing the clutch pedal will cause the throttle linkage to hang up and not return - at the worse time - it happened to me at a downshift at highway speed.

[joe912/62]

Thanks I'll look into this.

[joe912/62]

Look into the throttle rod linkage and it doesn't seem to be hung up on anything and still getting the same thing happening.
Would someone have a loner distributor that I can try before getting a rebuild or maybe purchasing a 123 ignition distributor. I'll pay for shipping here and back. It's an 82 SC

[ahh911]

I think my springs are worn as well. Advance starts to catch around 950 rpm and rpms rise to ~ 1050 especially with a warm car (I've had my timing light on to verify this), any small additional load (lights, or clutch engaged vs disengaged) will bring the rpms down. Currently rpm is set to ~ 850 warm, it's rock stable but it means the rpms can get low while the car warms up. Too bad someone has stripped my allen heads in the distributor, I'll have to dremmel the heads off or something.

Phil

[edjrbashian]

I have the same problem on my '75. Switched from CIS to EFI, then even a new motor/clutch. Brand new pedal cluster. Still have the issue come up from time to time. I am convinced it is something in the tunnel. Pulling back the throttle pedal doesn't solve it either.

Ed

[ahh911]

Ed,

EFI, does it have idle speed control capability through advance/delay timing adjustment?

Phil

[Schulisco]

Originally Posted by joe912/62

Having an issue recently with the rpm's going higher when at a stop light. If I step on the clutch and advance forward for a few feet the idle goes back down to 950+-.
Could it be a slipping clutch or something to do with the CIS?
Any help would be appreciated.
Joe

Check the vacuum limiter valve / deacceleration valve. Its the pneumatic valve with three vacuum connections, two thicker hoses and a control hose. Depending on the model year it resides left next to the throttle housing or on the right side of the motor, close to the fuel distributor. Part. no. 911 110 220 00 or 930 110 190 00.

Its operated by vacuum from the throttle. When releasing the throttle pedal it opens up to let flow metered air offside the throttle to prevent banging in the exhaust and to improve smog emissions. A high hanging idle leads me to this valve.

Thomas

[joe912/62]

I'll disconnect it to see if it helps. Mine would be the one above #6 cylinder on my 82SC. Would I have to block the hose end also?

[Schulisco]

Originally Posted by joe912/62

I'll disconnect it to see if it helps. Mine would be the one above #6 cylinder on my 82SC. Would I have to block the hose end also?

Yes. Otherwise there is additional vacuum leak...

[joe912/62]

Disconnect the vacuum line and went for a test drive. Seems to have worked. So is it the decel valve? Can I test it in the car?
Thanks

[pmax]

Congrats !

That's CIS and its gizmos.

In my 80SC, the PO or PM already had a golf tee stuffed into the "nipple".

[Schulisco]

Originally Posted by joe912/62

Disconnect the vacuum line and went for a test drive. Seems to have worked. So is it the decel valve? Can I test it in the car?
Thanks

Great outcome!
I would give it a shot of silicone spray in every of the three outputs to get the rubber diaphragm work again...and additionally moving it manually several times by using a vacuum pump on the thin control input...don't use WD40 or similar, they will damage the diaphragm for sure sooner or later. Only pure silicone spray! Repeat this several times if necessary.

Thomas