Chris@VetteFinders

Title should read WHEN COLD, not WHEN ROUGH. Geez.

My car runs terribly rough and belches tons of white smoke when I start it up cold. Almost feels like it is running on 6 cylinders. After about 5 minutes it runs perfectly smooth. Is it the choke? If so, how do I adjust that? Q-Jet


[Modified by Rhys, 6:08 PM 1/10/2002]

john's '81 mouse

Black smoke is fuel, usually too much.

Blue smoke is oil. (motor oil)

White smoke is usually anit-freeze/coolant, although I understand it sometimes might indicate automatic transmission fluid.

Sounds like you may have a leaking head gasket or worse, cracked head or block.

Are you loosing coolant?

Can have coolant tested for CO2 , which would confirm one of the coolant related problems detailed above.

Chris@VetteFinders

Nah, I am sure it is fuel related. I was just seeing it through my mirror. I check it again and it is not white. It is only when cold.

jvm

I also had white smoke at idle and when runing through the gears. on my 79 L82. Fixed it one day when looking at the centrifical weights that were all rusty. Except in two places. turned the rotor over and underneath was the missing rust. When the weights stuck it shot the timing . New distributor cap, rotor no more problemo. Check the easyisest first. Jim

Chris@VetteFinders

All distrib parts are new. I think that the fact it misses and idles rough until it warms up, then runs perfect points to the carb, don't you?

paso

Oh! yah how cold was it mid 80"s :D

Another thing to check is that the choke pull off is working .If it was working good before it could be that little diagham. It pulls the choke open just a little so it doesn't choke too much as it warms. You can check it with a hose and your mouth. When you suck it should pull the choke linkage. It's called a choke pull off Diapham. How cold again I want to hear it. :D


[Modified by paso, 6:14 PM 1/10/2002]

Chris@VetteFinders

I didn't say IT was cold, the car's engine was cold. It was "only" in the high 60's today though. :D

topless68

Rhys,

Definitely a choke pull-off problem. Remember, on cold start-ups, the chokes purpose is to raise fuel/air ratio to approx 5:1 b/c so little of the fuel makes it to the cylinder as vapor. It sounds as though your choke is not opening properly (possibly) and you are not getting any air, just fuel. That would explain the rich smoke. You will have to determine what kind of choke you have in order to adjust linkage.

Scenario #2 is just the opposite, the choke flap opens wide letting cold air rush the manifold with the cold fuel, and when the manifold heats, your idle smooths, (your choke is already wide open) and everything returns to normal.

Good luck!

Shutdown1

rhys,

Try manually choking your engine. Just take the air cleaner off and put a wet towell over the carb and crank it and see if it starts or runs better. I can't tell you how to adjust a '78 model, but at least this might tell you if the problem is in the choke or not. The first thing I would try it emptying a can of carb cleaner into the carburetor. I bet you don't drive that car much and the plugs could be fouled too, (if they're not brand new, knowing you!). Regards, and regards to all others who posted.


Also, while the engine is idling rough, try pulling the plug wires one by one to see if the problem could be isolated to one cylinder. I had a bad spark plug wire once that did fine when things warmed up inside the hood.


'74 Turbocharged 350 "Molested to Perfection," class of '71


[Modified by Shutdown1, 1:40 AM 1/11/2002]

Chris@VetteFinders

Thanks shutdown, I'll try that.

I don't think anything is gummed up. Just had the carb rebuilt by Lars, and basically everything is new on the top end including heads. Plugs look fine.


[Modified by Rhys, 10:03 PM 1/10/2002]

Nomad78SA

Hummm, looking in the mirror
Sounds like you need to drive it more often :seeya and look out the windshield. ok ok You just had the carb worked over not to long ago didn't ya? I would look at the choke myself.
Neil in Tenn

Chris@VetteFinders

I know you are kidding. I have driven it several days a week now that I'm "done".

Chris@VetteFinders

Lars emailed me this and I am posting it here in case it would help someone else:

Rough idle when cold, and then normal idle when warmed up, is usually a choke issue. Here's what you should do to check it out:

First, pull the little short vacuum hose off the choke pulloff diaphragm. Put a long vacuum hose on it that you can suck on. Suck on it, and verify that the pulloff doesm, in fact, operate (the lever should pull all the way in until seated). Also verify that it holds a vacuum - it should not leak. If it either does not pull in or does not hold a vacuum when you suck on it, you need to replace the choke pulloff. They run about $20-25 from NAPA. If you give me your carb number, I can give you a part number for the pulloff.

Once you have verified that it operates, or you have replaced it with a working unit, you need to verify its adjustment. To do this, either have the engine completely cold so the choke is fully closed (move the throttle open a crack to allow the choke to "set"), or push up on the choke intermediate lever to manually close the choke (this is the shaft and lever coming out of the back side of the round choke housing). With the choke fully closed, suck on the hose. The choke should pull open so there is 1/4" of clearance between the lower (forward) edge of the choke plate and the choke air horn wall. To adjust, turn the screw at the end of the choke pulloff linkage.
Let me know if you need further assistance.

Lars

Shutdown1

Very useful information. Thanks Rhys,Lars.