blyth18md

well i just got the carb back from the rebuild and the car runs but the idle is pretty high while in park.

in park and nuetral the car idles around 2K
and
while in reverse or any foward gear the car idles a little less than 1K

whats the deal?

Any body have good clear directions on how to adjust the idle, i know where the screw is, it just didnt seem to be doing much for me when i tried adjusting it.

AM Racer

If the idle screw isn't lowering the idle , then check that the choke fast idle cam isn't interfering.

Also, you could easily blow the trans by dropping it into gear while at a high rpm like that.

ronterry

I big rpm drop like that sounds like a vacuum leak assuming they didn't mess with the Idle A/F.

Ron

RB83L69

Sounds to me like your tach is screwed up.

2000 RPM is enough engine speed to run 60 mph on the freeway in your car. Is the engine really running that fast? Somehow I doubt it.

blyth18md

I was thinking the tach could be off too. but its definately alot faster than it should be. I mean when it drops to near 1K in gear it sounds to be alot closer to where it should idle. so im not really sure whats going on.

you said a vacuum leak could cause the big drop when changing gears, but would it be the initial cause of such high idle?

where is the most likely cause of a vacuum leak?

thanks guys, ill try to check all the vacuum lines, this is my first time really playing with the carb.

also with the idle screw, just for reference, how much should one full turn change the idle?

AM Racer

I'm thinking that something is holding the throttle open. To have a big enough vacuum leak to support 2000 rpm, it takes a bunch of fuel to compensate and the carb can't do it. The engine should stall first.

blyth18md

it could be.

this is my first time really playing with the carb.

took it off, myself.

Had it rebuilt

and put it back on myself.

but if sumthings holding the throttle open, why would it drop off by shifting into gear?

AM Racer

It drops because the trans is engaged in gear.

blyth18md

well i guess id better go play with the throttle cable and springs, make sure they arent kinked and are all set right.

anything specific i should look for?

know the little cylinder that sits in the from of the engine with the 3 lines that come off of it. (i forget the name right now). but could i cap off all those lines and the inlets on the carb to eliminate the vacuum issue? will the carb function the same without these lines connected?

AM Racer

I'd say turn the idle screw all the way out, look down the throttle with a flashlight and see if the blades are shut.
Remove the cables from the carb and see that they can extend enough manually not to pull the throttle lever.
Check the fast idle for the choke and see if it's holding the throttle shaft open.

blyth18md

screwed the idle stop all the way out.
blades are closed.
cables fit without pulling the throttle

how do i check fast idle?

also when i got the carb back i was givin TWO different mounting gaskets, was i supposed to use both?

-thanks
blyth

Madddog

I'm having the EXACT same problem. I actually have to shut the car off in D or R so that it won't "run on" and stumble like it does if I turn it off in P.

I suspect that my Fast Idle cam is missing, I just can't seem to find anything that looks like it...the screw is there but is ineffective. The cam itself was probably never put back on after a previous rebuild, but I've never worked on a Q-jet before this one so I don't know what the he!! I'm looking for

Can anyone post some close-up pics ?

Thanks !

blyth18md

sorry to hear about your situation, but glad im not in this boat alone.

If you figure anything out make shure you post up your results

thanks

slinkh

I had a similar problem about a year ago after my rebuild. Stumped me for about a week then I realized the throttle bracket wasn't resting on the idle screw when my foot was off the throttle. Turns out the bracket that actually holds the throttle cable was bent. I replaced it and it solved the problem.

Set your idle between 750 and 800 in park. When the car is in gear it should drop down to about 550 rpm.

To put your car on fast idle take off your air cleaner and use the throttle control to bring the rpms to about 1500. Then press the throttle plate so that it's closed while you release the throttle. as the throttle is falling release the throttle plate. RPM's will drop dramatically and then will come back up and stay on fast idle.

Hope that makes sense to you.

blyth18md

so the part of the bracket is supposed to rest against the idle screw? and when you move the idle screw the bracket should still remain against screw? If i were to back it all the way out the bracket would (should) rest against the piece of the carb where the screw is threaded through?

this is a CC quadrajet

slinkh

It shouldn't matter whether it's cc or not. That's the idea, by backing out the idle screw you're allowing the throttle control to come farther back. Theoretically if you backed the idle screw all the way out the return spring would pull the bracket all the way back.