Car acts like it has cruise, but doesn't

[Chas Henderson #28127]

My 71 sm auto was giving me trouble with the carb, so a few weeks ago I (after I consulted the board) I bought the choke pull off, new mounting gasket, cleaned the carb up so it look like new, and installed them. Car ran great. Two weeks later, When I drive the car, the accelerator acts like it sticking. So I checked the pedal and cable, and thats not the problem. It mostly happens when I am slowing down. The engine will not return to 600-700 rpms. so I have to brake harder and some times I have to goose the gas pedal. If the light goose doesn't work, I have to put it in neutral (the engine then goes to 1500prm) and give it a bigger goose. I thought it might be the C.E.C. switch, so I screwed it in so it couldn't make contact, but it still does it. On a level road, the car will creep up to about 39mph from about 35mph. I tuned up the car and its all up to spects. Timing is right on and so is the dwell. Idle is set to 600-700 and that what it idles at. The only other thing I have noticed is that befor this happened, when I reinstalled the carb and tuned it up was that the AC was working and now the AC clutch wont engage. So I am going to jump a hot wire to it just to check it out. I also had the car up on ramps to clean the underside of the car. I clean it about four times a year, and I did wipe around the wires going in to the auto tranny. They seem to be on tightly. I dont think there are any vacuum leaks.
Sorry this is so long, but I wanted to give you as much info as I could. Any ideals are welcomed.

Chasman

[Richard W.]

Re: Car acts like it has cruise, but doesn't

I had a similar thing happen once. It turned out to be the throttle return spring. Who knows?

[Chas Henderson #28127]

Re: Car acts like it has cruise, but doesn't

I thought of that, and I checked it out as much as I could. It seems to be strong enough. I do have a second spring, I could try and doubling them up. I keep thinking vacuum - tranny conection, but don't know how that would work.

I found out my AC clutch finally bit the big one. Some rubber piece thats part of the clutch has been shredding it self, so I took the belt off. Its the original compressor. So I need to buy a clutch, or ship it out for a rebuild. I wonder if I could fix it?

Chasman

[Larry S.]

Re: Car acts like it has cruise, but doesn't

I would not drive it untill you know for sure its not a linkage problem.If you think its over your head enlist the help of mecanic.Sometime and extra set of eye find it right away.

Good Luck

[adam schorr]

Re: Car acts like it has cruise, but doesn't

the throttle plate on my '70 LT1 got egg shaped & slightly worn. It causes the idle to be higher than normal sometimes. This may be unique to the Holley on carb the LT1. Just my $.02

[Jack H.]

Re: Car acts like it has cruise, but doesn't

If your '71 car's CEC is functional, that could be part of the problem. The CEC solenoid does TWO things simultaneously when it fires: (1) mechanically increases the carb's curb idle RPM via the solenoid hitting/bumping the throttle linkage, and (2) ports vacuum to the distributor.

Now, the upper end of the CEC solenoid has a foam filter surrounding the solenoid shaft. That's the mechanism that vents vac stored in the line to the distributor's advance. If it's plugged with dirt grease, it'll increase the time it takes for the distributor to vent vac and engine RPM's to die as a result.

Also, if prior owners have been 'tinkering' with the distributor to 'soup' the car up and they changed out the original vac advance mechanism, that could also have an effect. Since the '71 CEC system was intended to switch the distributor's vac advance in/out and give the car TWO idle profiles (one in low gear(s) the other in high gear(s)) the vac advance can for the distributor was intentionally designed to have a 'dead' at the bottom end. Earlier era distributors used a more aggressive vac advance that kicked in more quickly.

With manual transmission cars it's a bit easier to diagnose things. There, you take the car out, get it into high gear (3rd or 4th), then downshift to a stop and look for the idle RPM to return to where you set it during tune-up (about 700 RPM). If the engine is 'racing' at this point, you further test the system by putting the transmission in gear, keeping your foot on the brake and slowly letting out the clutch to load the engine and cause it to start to die...

But, before it dies, you push the clutch in and see if that caused the engine to return to the curb idle you set during tuneup. If so, you start looking for the problem:

(1) Dirty/defective CEC solenoid
(2) Incorrect vac advance can in the distributor
(3) Throttle linkage 'hanging'
(4) Weak throttle return spring
(5) Defective CEC solenoid control components including, transmission switch, thermal switch (RH cylinder head), bad CEC reversing relay, faulty interconnect wiring, Etc.

[Mike M.]

Re: Car acts like it has cruise, but doesn't

I recently fixed a Q-Jet on a '70 GTO with the same problem. The owner replaced the choke pull off and then had a case of sticking throttle. Problem turned out to be the fast idle screw. Because the choke pull-off was not working, "someone" screwed in on the fast idle screw to raise the idle to keep the car running. After installation of the pull off, the fast idle adjustment screw was in just far enough to catch the second step of the fast idle cam every now and then. Readjusted the screw by the proper procedure listed in the service manual and problem gone.
Mike

[Clem Z.]

check the fast idle cam

if the fast idle cam is plastic,some were, they are so light in weight that the air from the fan will move them into the fast idle mode. GM later put a metal weight into the plastic and even later went to a all metal fast idle cam. i am not sure of the year these changes happened

[Roger Legge]

Re: Car acts like it has cruise, but doesn't

There is probably a remote chance of this, but the idle will hang high and/or return slowly if the mechanical advance weights are not returning in a normal way. The advanced timing will raise the idle.

Roger

[Chas Henderson #28127]

Its fixed

Just a Short thank you to all that responded. I checked the fast idle screw and it was compensating for the failure of the choke pull off not working. I turned it down and reset the CEC valve ( I had tuened it down from touching the throttle) I had the car tuned up several years ago, And I believe it was set then. Anyway, it drives like it suppose to.

Chasman