I've experienced this problem once before and it stopped on its own until recently. This morning after starting the car (after it was sitting for 3 days with the weather around 60F degrees) I had to pump the gas pedal 5-7 times to get it started but once it started it started at a high idle which has happened before but I was able to tap the pedal to drop the idle speed. This morning, no matter how many times I tapped the pedal it continues to idle fast. So fast when I put it in drive I don't even have to give it gas to take off. It warmed up to about 180F and I put it in drive and floored it. That seemed to do the trick. It started idling fine after that. What is going on here? I have a 68 Cutlass Supreme with a Quadrajet that has a divorced choke. I recent had a leak issue with my fuel inlet which I sealed up. Before I sealed it up the car would not start at a fast idle. It would start at a low idle speed and I would hold down the gas pedal until it warmed up a bit. The car also surges once up to 45-50MPH after holding the gas pedal down about half way continuously. Once it gets over 50-55MPH it stops surging. I also have issue starting the car when its hot after its been sitting for over 45min-1 hour. The car is sometimes be very jerky when first accellrating or when slowing down. This only happens when the car is cold after being started up for the second+ time for the day usually after four hours of the first drive.

I know this is a lot of problems at once and I figure the right direction would be rebuilding the carb which I planning on doing in about a month. I have never rebuilt a carb before but am pretty mechanically inclined as long as I have good direction/pictures/diagrams to follow and it seems like there are a couple really detailed rebuild books for QJet. Thanks.

 

This morning, I tapped the pedal once to set the choke for cold start since it was sprinkling a little bit. The same thing happened. It was idling very very high and I waited until it got to 190F and tapped the pedal a few times with no luck. Once again, I had to put it in drive and floor it for it to knock down to normal idle. Whats going on here.

 

It sounds like the linkage is sticking. The carb may need more than a standard rebuild. The shafts could be loose in the base plate causing a misalignment and vacuum leaks. You may want to send the carb to a reputable builder to have it gone through instead of doing it yourself.

 

I would start by making sure the choke is set properly.

 

Thanks for the reply. Honestly, I know there is a pinhole leak somewhere around the fuel inlet because it was JB Welded back in there instead of being heli-coiled like it should have been. It was a quick fix to be able to use the car to commute to work and back when it failed last month. I am getting another 68 QJet which the seller claims just needs a basic rebuild. That way I can at least use the car while cleaning/rebuilding. I called my local carb guy when I needed to get the fuel inlet heli-coiled last month. The guy wanted $400 for a rebuild and $250 for the heli-coil. That sounds a bit ridiculous to me so I went another route. I attempted a self-tapping inlet fitting and it did not fit properly. At last, I didnt have much of a choice but to cover the threads with JB Weld and permanently put it in there.

This being said, if a vacuum leak is the issue, wouldnt it stay at a high idle at all times? Like I mentioned earlier, it will kick down but only after I put it in drive and floor it for a second or two.

 

The vacuum leak will cause the surging issues, but the misalignment could cause the fast idle cam not to have enough room to kick down properly.

 

Sometimes the plastic weighted fast idle cam just gets gummed up with grease and stuff and doesn't want to fall back down when you kick it down. A good blast of GumOut usually does the trick pronto.

As for surging, don't forget the possibility that could be a timing issue (basic timing, sticking mechanical advance, hole in advance diaphragm).

- Eric