Why does the idle keep increasing?
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Le Mans Master
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From: Westfield Indiana
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Why does the idle keep increasing?
I started up the 79 today after letting it sit for a week and it would not idle below 1500. Last week (and the previous few months) the idle would not go below 1000. It doesn't get driven too often but it does get driven in the winter. I don't want to drive it today since the roads are terrible, but I did let it run for about 20 minutes and the idle would not drop down, no matter what. I tried adjusting the idle and it would neither increase or decrease. :confused: It seems as though it has been slowly increasing over the past few months. It even diesled after shut off today. It's never done that before. I checked the timing a couple weeks ago and it was fine. 14 at idle, 34 full mechanical, all in by 2500. Could I have an ignition problem that's slowly creeping in? If so, how do I check it out? Any other suggestions?
Le Mans Master
Joined: Sep 2000
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From: Orlando Floriduh
Re: Why does the idle keep increasing? (sharklover)
It is probably on the fast idle cam... On the choke side of the carb there is a small screw buried in the maze of linkages near the bottom. This is the adjustment for fast idle and there is a stepped cam that it rides on. Check it out. :yesnod:
Safety Car
Joined: Jun 2001
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From: Severna Park Md
Re: Why does the idle keep increasing? (sharklover)
I think the choke is just hangin in longer with the colder weather. Did you try a quick punch of the pedal down to the floor to help it drop down. Is it an electric choke?
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Le Mans Master
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From: Westfield Indiana
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Re: Why does the idle keep increasing? (Jvette73)
Yes, it's an electric choke and I tried many punches of the throttle to try and get it to idle down after it had sufficient time to warm up. Water temp was at 200 but it simply would not idle down.
Safety Car
Joined: Jun 2001
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From: Severna Park Md
Re: Why does the idle keep increasing? (sharklover)
Got 12v to the choke housing when the key is turned on? If so, one thing you can do is rotate the choke housing to take tension off the butterfly. This will make it open up sooner. Gumed up linkage behind the choke housing could be a culprit too.
or the electric choke itself could be bad
[Modified by Jvette73, 11:41 AM 1/21/2002]
or the electric choke itself could be bad
[Modified by Jvette73, 11:41 AM 1/21/2002]
Drifting
Joined: Mar 2001
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From: St. Louis, Missouri
Re: Why does the idle keep increasing? (sharklover)
If it's a stock '79, chances are is that it does NOT have an electric choke. I'd check for a vacuum leak. Check every hose. My '79 had a high idle when I bought it. Turned out Bubba sliced two vacuum lines to the charcoal cannister and didn't bother plugging them.
Team Owner
Joined: Jul 1999
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From: Huntersville NC
Re: Why does the idle keep increasing? (sharklover)
One other easy thing to check. Remove air cleaner and base and make sure the accelerator cable and linkage is not binding. I had this very simple problem which caused the engine to race - anywhere from 2k to 2500 rpm. Horrible dieseling when I turned the engine off. It would run on, cough, spit, and smoke for 5 seconds before it would die. All kinds of carb problems were diagnosed until some kind soul showed me the scrape marks on the bottom of the air cleaner base where my throttle linkage was scraping. Bubba fix was to add a 3rd accelerator spring which forced the throttle closed. Later I simply bent the linkage out of the way so it cleared the base. MJ
Racer
Joined: Jun 2000
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From: new mexico
Re: Why does the idle keep increasing? (sharklover)
After reading all those fixes I have yet another thing to look at. My 79 did the same thing. Traced it back to sticking springs on the centrifical weights. They were rubbing on the top of the rotor cap!! Anit vettes fun? Jim
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Le Mans Master
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From: Westfield Indiana
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Re: Why does the idle keep increasing? (jvm)
Lots of good ideas. It is not a stock 79. It has an Edelbrock Performer RPM manifold and it has been modified and has an electric choke. I have been very busy today since I posted this topic and have not had time to further research the problem. I will be moving the vette to another garage tomorrow(it's great to have a selection but it sucks when all the apartments are rented), and I'll look into it more then. The weather is also supposed to be great tomorrow (58) so I'll probably go for a short drive and see if I notice any other problems.
Thanks
Thanks