Author Topic: QJet High Idle wont kick down  (Read 7903 times)

Offline Joed1191

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QJet High Idle wont kick down
« on: October 24, 2016, 06:23:17 AM »
Just bought a 1978 Cutlass Supreme with a Chevy 305 and a Rochester Quadrajet with hot air choke. First disclaimer, I am only 24yrs old and a Carburetor "newbie" so I'll do my best. Bought the car a couple weeks ago and drove it a few times since then; about 60 miles total. Drove and ran perfectly fine, smooth idle and no smoke. Last time I drove it, it started up fine and idle was ideal. Put it in drive and got on the trottle (basically to the floor) for about 5 seconds and then let off, car continued to accelerate and had to work the brakes home. Now, every time i start it up, it runs higher than supposed to (my guess would be 1000-1200 rpms, and also very rich, strong gas smell with some white smoke from exhaust). I have checked for vacuum leaks, sprayed down all linkage (throttle, choke, fast idle), throttle cable is not sticking, return springs have enough tension. Another note is the throttle linkage is not making contact with the idle adjustment screw on the driver side carburetor. I can force it down (pulling towards the grill) but it is tough. My guess the throttle plates are sticking? Like I said before I am new to carburetors and appreciate the help!

Offline carmantx

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Re: QJet High Idle wont kick down
« Reply #1 on: October 24, 2016, 06:06:01 PM »
Make sure your choke is completely open so the fast idle cam is not engaged.
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Offline Joed1191

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Re: QJet High Idle wont kick down
« Reply #2 on: October 24, 2016, 06:30:48 PM »
So after messing around with it I noticed that if I push down on the fast idle cam linkage, it opens the choke butterfly and the throttle plate returns to the idle screw. As soon as I pull on the throttle plate (as if I pushed on the gas pedal) the choke plate closes and the throttle plate won't make contact with the idle screw anymore. What does that mean?

Offline omaha

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Re: QJet High Idle wont kick down
« Reply #3 on: October 24, 2016, 07:17:28 PM »
could be a choke adjustment. try disconnecting the choke linkage temporarily and see what happens.

Offline Joed1191

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Re: QJet High Idle wont kick down
« Reply #4 on: October 24, 2016, 07:39:19 PM »
My only question is if it was running perfectly fine before, why not now? Just to reiterate, started the car idled fine, put it in drive, after 10 seconds, basically floored it and now it won't kick down.

Offline Mudsport96

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Re: QJet High Idle wont kick down
« Reply #5 on: October 25, 2016, 03:50:47 AM »
Did the vacuum line for the hot air choke pop loose? Maybe the bimetal spring popped off the choke actuator in the housing.

Offline Joed1191

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Re: QJet High Idle wont kick down
« Reply #6 on: October 25, 2016, 07:49:16 AM »
I double checked the vacuum ports and lines to make sure they were all hooked up and they are good. i will check the choke spring. Can someone explain the high idle cam and choke mechanism (in layman's terms). I push down on the high idle cam linkage and the choke plate opens and throttle plate returns to the idle spring. I open the throttle plate and the choke closes and the throttle plate wont return to the idle screw

Offline Mudsport96

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Re: QJet High Idle wont kick down
« Reply #7 on: October 25, 2016, 09:11:48 AM »