Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

'81 Long/Random High Idle(s)

<< < (3/3)

MP81:
All right, so I had a chance to start it yesterday.

Of course, it didn't do the typical thing. As I let it idle, I noticed it was sitting around 1k-1100 or so, until I pushed the lever (arrow in pic) down, and the idle dropped right down to about 700 or wherever it is supposed to idle (did not take much effort, just a light touch).

It also seemed, at least in this instance, that revs "sticking" or being slow to drop was solved just by making sure the throttle linkage was pushed all the way back to closed, maybe a little sticky (though I thought I did lube that last year).

I'd still like to see it jump up to 2k while I'm underhood though and see what flips like a switch when that does happen. Maybe it is related, though...

MP81:
Playing around with this yesterday, that same "arm" basically stayed stuck up, until I pushed on it, and it dropped past whatever was holding it up. Was holding idle about 1000-1200 or so. Once it dropped down, she sat an idled at about 750 for the whole rest of the time - aside from when the throttle would stick it up higher, but that was easy enough to unstick (and diagnose).

As far as the super-high 2k rpm idle that came on like a switch...haven't seen it the past two times. Got me thinking - what if the vacuum solenoid that opens the flap in the air cleaner for the heat riser has been the culprit, causing a big vac leak all of a sudden - the past two times I've run the car, I've had the air cleaner off, and that vacuum port plugged. I don't need it, as I have headers, so I think I will maintain that and see.

Cliff Ruggles:
Once the fast idle cam drops to the lowest position it should stay there until the choke raises it again.  If it's coming back up while driving around with a hot engine the choke is defective......Cliff

MP81:
I have to confirm, but I don't think it's popping back up - I think it is getting hung up, rather than dropping down. When I pushed on it, you could tell it was under pressure to drop down, but wasn't able to because it was stuck up, though I'm not sure on what.

Choke is brand new (ordered from here), and it did this with the old choke, as well.

Cliff Ruggles:
If it's never dropping to the lowest position and getting hung up, then remove the housing and clean/polish/lubricate all the associated parts.  Make sure nothing is bent and touching or rubbing on something it's not supposed to.

Put it back together, make sure the pull-off isn't hitting anything it's not supposed to, and if it is bend the linkage or at the bracket to get the clearance you need (common practice here).

I'd remove the lock-out and discard it, just another thing that can hang things up and isn't needed.  Make sure the parts on the primary throttle shaft are installed correctly and intersecting the choke parts correctly when they need to.

Once all that is done it will work flawlessly, or it should assuming all the parts are correct on that side of the carb.....Cliff

Navigation

[0] Message Index

[*] Previous page