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#26 |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
untill now that didnt help. Will try again 2night!
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#27 |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
checked 2nite and the fast idle cam is clear as far as I can judge. I tested it and the fast idle cam is not keeping the linkage from going to full idle...
I did notice something else. I made a bracket to change the springs into pulling opposit to the throttle cable, so the throttle shaft is relieved of stress... here are some pics of the setup sofar: the thing is....I drilled several holes to be able to adjust the spring tension...but even the biggest tension will not pull it back to the idle screw...al the way.. I did notice this evening that when the engine is warm and not running, the linkage runs free and very easy...when I start the engine...the last bit of the linkage seems to move less smooth... man...what can this be....
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#28 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
Where's your vacuum advance hooked up to?
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#29 |
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Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
manifold vacuum, because I have all the pollution stuff taken of.
why? do you think there is a connection?
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#30 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
Hook it back up to a ported source. Idle will slow down.
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#31 |
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Join Date: Apr 2011
Location: corpus christi, tx - america's fattest city
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Second. Distributor advance and the transmission modulator need to be fed from the carb, know this from experience.
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#32 | |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
okay, thanks, did just that and indeed idle slowed down...
but it did not solve the problem, that the last piece of my linkage feels heavy and it does not return all the way easily when the engine is warm and running. The only thing it changes is that it wil not advance as much in idle, wich causes less efficient burning of fuel...better would be to have it hooked up the right way and reduce fuel consumption by dropping the idle down by adjusting the screw for it. So I am gonna reconnect it to manifold and continu my search for the problem....solution... heres some info on type of vacuum too choose: Quote:
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#33 |
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Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,359
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Re: Quadrajet, high idle with warm engine
Hi kikkegek,
I think someone might have mentioned this earlier, but have you checked the throttle shaft to see if it's loose? It's a common problem for the throttle shaft holes in the baseplate to get worn ... especially on high mileage Q-Jets. That creates a vacuum leak and I believe it can also allow the throttle shaft to get out of alignment just enough for the throttle plates to catch a little bit. I had this happen with the Q-Jet on my Nova. I had to tap the throttle to get it to idle down. I did some checking and ruled out a sticking cable, fast idle cam, and so on, but noticed that the throttle shaft was rather loose. Fixing the worn holes in the baseplate with some home-made teflon bushings solved the problem. I picked up the home-made teflon bushing trick from Dave Ray (IgnitionMan) on another forum ... he describes it in post #9 ---> http://www.hotrodders.com/forum/weir...ems-78607.html |
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#34 | |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
Quote:
The shaft can move just a little from side to side...but I dont really notice any serious wear...I think... problem is, if I take of the carb, the engine wont be running, and the linkage would run free, so how am I gonna find the the cause of it not returning to full idle... I contacted ignitionman, maybe he can help me with the teflon mad...I dont really understand it. Do you have any pics of how you did it?
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#35 |
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Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
So know we've found your problem. Due to throttle shaft bushing wear the side to side movement causes the primary throttle plates to hang up on the bore. It can be fixed but you'll need to find an expert that's done it before.
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#36 |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
I am not 100% sure, because when the engine is off and cold I have no problem...but it could be...how can I check this?
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#37 |
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Location: Bowser
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Re: Quadrajet, high idle with warm engine
Pull off the carb, flip it over and see how the throttle plates fit in the bore. Move the throttle shaft back and forth and see where it hangs up.
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#38 |
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Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
I'll probably do just that...just need to find some time for it, since we drive it daily...
I'll be back!
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My dreamride / project:1977 GMC C15 Suburban In storage: Monster - 1974 GMC Suburban 25hundred Sold : Chevrolet Suburban K20 Silverado 1986 Guide: real HID projectors for 4x6 headlights link: DIY LED TAILLIGHTS |
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#39 |
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Location: Maumelle, AR
Posts: 478
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Re: Quadrajet, high idle with warm engine
Have you tried adjusting the choke thermostat one or two clicks to LEAN? Might want to give that a try, if it doesn't help you can return it to where it is now.
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#40 |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
Hi PRattenbury,
I checked 2nite and it is already in the leanest position I think: look at this pic. Is the silver stip on the black cover the indicator? ![]() I turned even a little further, lets hope it helps. I need to take it for a drive. Because with the engine now cold and off...the linkage is just fine..
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#41 | |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
Quote:
I guess there is nothing left, but removing the carb and doing some reasearch on it!
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#42 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
Or just enjoy it the way it is. Experimenting with your carb throttle plate could leave you with nothing to drive. When I worked on mine I had several spares. You probably don't or have access to any.
Or find a rebuilt and put that on. |
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#43 |
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Join Date: Mar 2011
Location: Dallas, Texas
Posts: 920
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Re: Quadrajet, high idle with warm engine
Is your electric choke working?
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#44 |
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Join Date: Aug 2010
Location: Netherlands, The Hague
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Re: Quadrajet, high idle with warm engine
No. i think it is disabled. Since you need one when driving LPG.
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#45 |
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Join Date: Jul 2007
Location: Tucson, AZ
Posts: 3,188
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Re: Quadrajet, high idle with warm engine
I am wondering about the loose throttle shaft/bad bushing theory. If jabbing the accelerator causes the engine to idle normally, how would a loose throttle shaft (and associated vacuum leak) cause the high idle? Isn't the throttle shaft still loose after you jab the accelerator? Wouldn't it still have a high idle after jabbing the accelerator? Makes me think some kind of mechanical linkage problem is the issue.
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#46 |
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Join Date: Mar 2011
Location: Dallas, Texas
Posts: 920
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Re: Quadrajet, high idle with warm engine
I personally gauruntee you that if you turn that choke on your problems will dissapear. The high idle of the electric choke will only go off when the choke has power and is functioming correctly.
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#47 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
With a loose throttle shaft the throttle plate hangs up on the bore. If you stab it hard it slams shut. More closing force puts it back where it belongs. Gentle throttle movement allows it to hang up.
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#48 |
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Join Date: Jul 2007
Location: Tucson, AZ
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Re: Quadrajet, high idle with warm engine
OK, thanks geeser- play in throttle shaft causes hangup - nothing to do with vacuum. I detect no play in the throttle shaft from up top inspection, and it did this since it was "professionally" rebuilt" about 2 years ago.
MadManAndrew - I have a manual choke on mine, and I can physically verify that it is wide open when the high idle occurs. So what do you think would be my problem? (I mean my truck's problem, not me personally. ![]() |
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#49 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,600
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Re: Quadrajet, high idle with warm engine
The hang up isn't consistent either. When I fixed mine I found where the plate was hanging up and used a dremel to provide a little clearance. Bushing kits and plate screws wheren't readily available then back in the 80's so I didn't go that route for a fix.
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#50 | |
Custom Sport W/T
Join Date: Nov 2010
Location: Tarpon Springs,Fl & Annapolis,Md. ....................Quaint drinking villages with a fishing problem
Posts: 898
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Re: Quadrajet, high idle with warm engine
Quote:
Last edited by CaptRMW; 04-24-2011 at 11:32 AM. |
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