71MonteCarloMD Posted July 29, 2013 Share Posted July 29, 2013 I need your help in troubleshooting my carb as it starts up quite well - idle very well at beginning but idle gets rough when engine gets warmed up. I took pictures of before starting engine and after engine warmed up - not sure if that's normal? I pulled the switch back assuming it's the choke, the idle improved - here's the picture of switch with yellow circle that I pulled back. How do I fix this issue? Rick Quote Link to comment Share on other sites More sharing options...
Murphy Posted July 30, 2013 Share Posted July 30, 2013 Rick, get it rebuilt! I have the same carb as you (divorced choke) with similar issues. The linkage just didn't work smoothly. After the rebuild by an expert Q-Jet guy, this carb operates beautifully. Read the post under "General tab - Qjets & Doug Roe". My cost has $140. Quote Link to comment Share on other sites More sharing options...
Mike Brichta Posted July 30, 2013 Share Posted July 30, 2013 Hey Rick, When you say "idle improved" do you mean the issue was resolved at that point? It sounds like your choke is not opening when the engine warms up. On your style carb that is controlled by a spring coil in the intake. It's right next to where you drew the yellow circle. The spring expands as the engine warms up and pushes a rod which opens the choke. It is hard to explain what it looks like. If you remove the screw which holds on the cover you can inspect it to see if it is working correctly. Hope that helps. Quote Link to comment Share on other sites More sharing options...
tom71 Posted July 30, 2013 Share Posted July 30, 2013 I think the rod that comes out of the coil spring should be perpendicular to the carb. The picture shows it at a rather severe angle. Are you sure that coil spring is installed correctly? It looks backwards to what mine looks like on my '71. If that coil is not working properly it will choke the carb and cause problems. Hope this helps. Tom Quote Link to comment Share on other sites More sharing options...
wallaby Posted July 30, 2013 Share Posted July 30, 2013 I see the linkage arm binding where it comes out of the cover also, but in the photo it looks like the choke is fully open when the engine is warm. The photo of cold engine shows a less than fully closed choke, but a touch of the throttle may let it close fully, and the problem of poor running isn't when the engine is cold anyway. So we need to know when the poor running problem really happens. Is it when the engine is fully warm, or somewhere in the transition between cold & warm? From your post, it sounds as if the problem is after the engine is fully warm only. If that's true, and the photo shows the choke plate fully open, then the problem could be as simple as adjusting the idle mixture screws to get a smooth idle....probably turning them out to richen the mixture. Try to adjust them both about the same. Here is a photo showing where the mixture screws are located: Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted July 30, 2013 Share Posted July 30, 2013 that choke coil cover is in backwards for a start and probably some of the problem the choke coil is 90 degrees off what mine is on my '70 small block? Quote Link to comment Share on other sites More sharing options...
Murphy Posted July 30, 2013 Share Posted July 30, 2013 Mark, looks like an 800cfm from an Olds....right? Any clearance issues with the fuel inlet? Quote Link to comment Share on other sites More sharing options...
wallaby Posted July 30, 2013 Share Posted July 30, 2013 That's not my carb, but just a photo I grabbed to show where the mixture screws are found. Chevy and Olds, Pontiac, etc had different fuel inlet locations but the idle screws are all the same. Quote Link to comment Share on other sites More sharing options...
tom71 Posted July 31, 2013 Share Posted July 31, 2013 Sam is right in observing the coil cover is on backwards. That would fix the severe angle of the arm. I purchased a new coil spring thinking that was the cause of my cold choke problems. I recieved a coil that was opposite of what I wanted. I put the coil in the freezer and verified it coiled opposite of what our cars needed. Put the old coil back in and set the choke. All OK. I suggest checking the coil spring and making sure it is not working opposite of what you want. It could be choking off the carb. Good luck. Tom Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted July 31, 2013 Author Share Posted July 31, 2013 Mike/Mark/Sam/Tom - thanks for the tips, I took the coil cover off and changed the arm to go from angle to "straight" but it didn't help with idling, it kept stopping running - see picture I took without coil cover - does this means that I need new coil? [img:center]https://plus.google.com/u/0/photos/11600...184843726948689[/img] Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted July 31, 2013 Share Posted July 31, 2013 is the choke completely opened when warmed up? yes...then there is other problems how far are your idle jets open? Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted July 31, 2013 Author Share Posted July 31, 2013 Sam, with arm modified, the choke is nearly closed when warmed up - haven't checked when cold yet. If you are referring to adjustment that Mark posted picture of carb? If so, they both are equally opened 3/4 way out - I tried to adjust them equally all way to end which didn't make any difference. What am I doing wrong? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted July 31, 2013 Share Posted July 31, 2013 3/4 of a 1 turn? that has to be the wrong choke coil then, I'd wire the choke open and see if it idles first, worry about the choke after you get it running correctly Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted July 31, 2013 Share Posted July 31, 2013 Have you tried checking the engine vacuum? From the first post it seems as if the closing of the choke plate makes it idle well, although when it starts to open the carb starts to fail? Does it idle at all? Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted July 31, 2013 Author Share Posted July 31, 2013 Sam - it was late in the day for me yesterday that I didn't quite read your question correctly, I did not touch the idle-mixture screw if you are referring as idle jets (see link below for picutre)? If yes, I will try again with the idle mixture screw (not the ones that Mark pointed out). Idle Mixutre screw-Rochester Q-jet Rick Quote Link to comment Share on other sites More sharing options...
stangeba Posted July 31, 2013 Share Posted July 31, 2013 I found several vacuum leaks from items attached to small rubber hoses from my 71 Quadrajet, like the vacuum door on the air cleaner and the evaporative emissions canister on the driver side ft radiator support. I suggest you unhook them, plug the opening and see if there is an improvement. A better way would be to use a vacuum hand pump with a gauge to test these items but few people have them. Other vacuum leaks may be at the brake booster or it's hose, the PCV valve hose or the intake manifold gasket itself. Evap Emissions canister picture Several vac hoses 71 350 4BBL pic Carb picture carb picture PCV hose pic Quote Link to comment Share on other sites More sharing options...
Murphy Posted July 31, 2013 Share Posted July 31, 2013 Rick comparing some of your pictures it appears that the vacuum advance is connected to the wrong port. Bruces picture is correct. But possibly it doesn't make a difference?? Hopefully someone will confirm...... Quote Link to comment Share on other sites More sharing options...
stangeba Posted August 1, 2013 Share Posted August 1, 2013 Ported spark, like my picture, does not allow vacuum to the dist vac advance till you step on the gas. From the factory, my car used ported spark BUT there was a solenoid (I removed it in 1971) that closed off the ported spark till the trans was in high gear or reverse for testing purposes. This is an emissions related set up most have now bypassed. With full intake manifold vacuum, you may have an idle that is a bit too fast and not controlled with the idle speed screw. If someone were to set their timing with the hose hooked up to full intake vacuum, the setting is wrong where ported shouldn't matter since there isn't any at idle. Lot's of places for a vacuum leak, look carefully for several of them. I was surprised how many I had and the car still ran OK with a bit of a rough idle. Bruce Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 1, 2013 Share Posted August 1, 2013 That last photo is a good angle. Do us a favor and shoot that twice again: A: engine cold before starting. And B: fully warm with engine running. From that we should be able to cut through some of the confusing guesswork. I'm wondering if the choke pull-off is working. The job of the choke coil is to CLOSE the choke when the engine is cold. Once you start the engine the choke pull-off tries to OPEN the choke, and the two play tug-o-war until the choke coil relaxes and the pull-off wins out. The choke coil is not designed to open the choke by itself. Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted August 15, 2013 Author Share Posted August 15, 2013 Mark - was on vacation and don't think I'll have chance to work on my Monte til Sept so will upload photos when I can. I am curious if I have the choke coil in right place? Thanks again, Rick Quote Link to comment Share on other sites More sharing options...
71MonteCarloMD Posted April 20, 2014 Author Share Posted April 20, 2014 Thanks guys - a friend helped yesterday, choke was not the issue as he tweaked the carb little which idled better. My son and I plan to work on the coil by putting it in right place at another time as it's running fine Quote Link to comment Share on other sites More sharing options...
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