Question: Possible Choke Problem

[Dunzvett81]

Hi all, Have an 81 and think there is a choke problem. Here is the situation: When I start the engine cold the choke comes on with the blade almost closed, open about quater of inch. Seems to work ok with rmps increasing up to 2000. Now my problem, I can't get the rmp's to come down even with tapping the gas pedal. (the choke blae is fully open straight up and down) I have to manually touch the top cam with my finger to kick down, then again to get to normal idle speed. If I drive the car is seems the top cam comes down but never all the way. When engine is warm, curb side idle is about 1000 unless I touch the cam again to make it go down to normal about 700. It seems to be sticking. Any ideas, thought or solutions?? thanks Jay

 

[GerryLP]

Jay,

The most simple and quick way to get rid of sticky mechanism is to clean them with a carburetor cleaner (spray, O2 sensor safe type). It sounds like the stepped-lever maybe a little sticky. It is not the only thing that can cause the condition, but it is the most common.

GerryLP:cool

 

[Dunzvett81]

Gerry: Once again you came to my rescue! I sprayed the hell out of the linkages and the step-lever mechanisms with a good carb spray. This has seemed to help and appears to be working. I also sprayed the carb and it too seems to be running even more smoother. Thanks a lot! now only if you can help with my engine tick!! when i rev you can hear this (only way to describe it is a ticking noise from front of the car) I checked all the vacums and exhaust for leaks. I actually found a small leak being a very little hole in the pipe by the cat convt. I ordered a new one. The rest of the exhaust is A1. When I listen to the valve covers it sounds like it is coming from that area.
Thanks Jay

 

[GerryLP]

Gerry: Once again you came to my rescue! I sprayed the hell out of the linkages and the step-lever mechanisms with a good carb spray. This has seemed to help and appears to be working. I also sprayed the carb and it too seems to be running even more smoother. Thanks a lot! now only if you can help with my engine tick!! when i rev you can hear this (only way to describe it is a ticking noise from front of the car) I checked all the vacums and exhaust for leaks. I actually found a small leak being a very little hole in the pipe by the cat convt. I ordered a new one. The rest of the exhaust is A1. When I listen to the valve covers it sounds like it is coming from that area.
Thanks Jay

Jay, if you get a 1/2" diameter rubber hose and pop a very small funnel at one end, you have a make-shift stethoscope. This can help you make sure it comes from a specific area. However, If you are hearing the "ticking" sound while having the air cleaner removed, then the ticking noise is most likely the mixture control solenoid. Place the air cleaner back on, and it should muffle a lot of it down.

If you are still hearing a loud ticking sound after placing the air cleaner back on the engine, then the ticking sound could be coming from one of the lifters "sticking" semi-collapsed (<---this word actually sounds worse that it actually is)and the ticking noise is the slop between the lifter and the push-rod and the valve rockers.

GerryLP:cool

 

[dmdodd]

Gerry: ... I sprayed the hell out of the linkages and the step-lever mechanisms with a good carb spray.

Jay - what good carb cleaner did you use? GUNK or something better?

I've just noticed that the secondaries on my '79 L-48 Rochester don't open at all, and am thinking I'll try some cleaner first to make sure the linkages aren't stuck. It also seems like the choke is sticking a little too (as wouldn't idle lower than 1200 rpm earlier).

I wonder if spraying the hell out of the engine with brake cleaner spray (as recommended by my mechanic) this weekend during my valve cover change removed some vital lubricants.

GerryLP - I'll try this carb spray first, but any other problems associated with secondary paddles not opening?

Cheers!
~Dan

 

[Dunzvett81]

I used KLEEN Carb & Choke cleaner. It took a few times before it loosened up. Like I said I spray the hell out of it and then worked the cams by hand. I also had a slight hesitation (bog) at acceleration. Once again I sprayed the hell out of the carb and I the bog was gone. smooth as silk!! What I thought was going to be a painful carb re-build turned into about $8.99 fix (for now!! there is always something!) good luck

 

[Vettehead Mikey]

Jay
I've just noticed that the secondaries on my '79 L-48 Rochester don't open at all, and am thinking I'll try some cleaner first to make sure the linkages aren't stuck. It also seems like the choke is sticking a little too (as wouldn't idle lower than 1200 rpm earlier).

What makes you say that they're not opening? They do NOT open with the car revving in neutral.

 

[GerryLP]

... but any other problems associated with secondary paddles not opening?
Cheers!
~Dan

Dan,

What makes you suspect the secondaries not opening? They open as a function of load -not RPM.

But when they open, one can tell. 1st, listen for that low range sound when you stomp on the gas pedal, and 2nd, you'll see the gas gage needle move toward empty...:L

GerryLP:cool

 

[dmdodd]

Well I had a car-knowledgable friend over today to look at the engine as I'd just changed the valve covers for the first time and was seeing a lot of oil smoke from both sides of the engine, though he informed me it wasn't as bad as I'd thought and would go in 30 mins of driving.

Whilst he was looking at the carb he was asking me to rev it hard, punch it etc, and said the secondaries weren't moving a budge.
Personally I didn't realize that secondaries didn't open from RPM alone (this is my first Vette and first carb-operating car, so my knowledge is thin on the ground to say the least!), but even punching the throttle had little effect.

The friend played around for a few minutes and got them to open a small amount under high load (may be 1/4" at most), but said they should open way more than that.
What should the secondaries open to, should I actually be seeing a 45-90 degree lift in the paddles/plates or something closer to 10-20 degrees?

Thanks again for all the help guys, again, Vette is 3 weeks old (to me) and I have no previous knowledge of carburetor'd cars. :W

~Dan

 

[JohnZ]

Whilst he was looking at the carb he was asking me to rev it hard, punch it etc, and said the secondaries weren't moving a budge.~Dan

The secondaries will only open under load, while driving the car; they won't open just revving it up in the driveway.

 

[dmdodd]

Ah ha, we're getting somewhere. So you shouldn't see even a little flicker of secondaries whilst in "park" and revving?

My mechanically-minded friend needs updating then!
Just bought some carb cleaner from NAPA so will blast the carb for good measure all the same, as choke seems to be sticking even after tapping the gas pedal.
Thanks JohnZ and all who've posted - I've a lot of learning to do!


~Dan

 

[Vettehead Mikey]

Ah ha, we're getting somewhere. So you shouldn't see even a little flicker of secondaries whilst in "park" and revving?

My mechanically-minded friend needs updating then!

Having them 'flicker' under those conditions will most probably make them open far too often and too soon under actual driving conditions, inducing the dreaded Quadrabog stumble that follows bubba around most of his life.

Best have your friend step away from the car till you get a shop manual.