I have a 72 chevelle mild 350.

There are times when I turn off my car and it will do something like, "..putt..putt..puttt..then like a sound of air comin out, like taking a last breath, when it does that, I have trouble starting it up. It will do this out of nowhere so I cant really tell why its doing so. Checkd gas, it was full. so not running out of gas..Im thinking maybe a new carb but not really sure.

When shes sits for about a couple days or say, specially in cold weather, pump pupmp gas turn key she start up, but takes awhile for here to warm up. (10-15min) once idle goes down then I know whes warm to go.

I have a 72 chevelle mild 350.

There are times when I turn off my car and it will do something like, "..putt..putt..puttt..then like a sound of air comin out, like taking a last breath, when it does that, I have trouble starting it up. It will do this out of nowhere so I cant really tell why its doing so. Checkd gas, it was full. so not running out of gas..Im thinking maybe a new carb but not really sure.
Run-on (sometimes called "Dieseling") is usually caused by too-high idle speed.

Secondary issues would be too-hot engine temperature; too-low octane rating; or a bunch of carbon in the chamber. Basically, anything that causes hot-spots in the combustion chamber that can ignite the fuel without having a spark at the spark plug.

When shes sits for about a couple days or say, specially in cold weather, pump pupmp gas turn key she start up, but takes awhile for here to warm up. (10-15min) once idle goes down then I know whes warm to go.
Verify that there's fuel in the bowl before starting; and if so--time to adjust the choke. There's NO need for a 10 minute warm up before driving the car--although--you do want to be easy on the ol' girl until the WHOLE DRIVETRAIN is at normal operating temperature.

I had the same issue that would happen at random times. It ended up being the pins that hold the weights in the distributor had come lose and caused the timing to move around at random. I replaced alot of parts before I figured that one out. So if you check the timing, don't just check it at idle but rev it some also. Pins can get a groove worn into them as well as the hole in the weights can get ovaled out.

Run-on (sometimes called "Dieseling") is usually caused by too-high idle speed.

Secondary issues would be too-hot engine temperature; too-low octane rating; or a bunch of carbon in the chamber. Basically, anything that causes hot-spots in the combustion chamber that can ignite the fuel without having a spark at the spark plug.


Verify that there's fuel in the bowl before starting; and if so--time to adjust the choke. There's NO need for a 10 minute warm up before driving the car--although--you do want to be easy on the ol' girl until the WHOLE DRIVETRAIN is at normal operating temperature.



sorry to be so clueless but fuel in the bowl means? heh and anywhere I can find out how to adjust the choke on a edelbrock ?

what would help with having too much carbon in the chamber? would buying a new carb do? I would rather try anything else besides buying one but If I was force to then I guess I will.

I got stuck at the store 1 time and it sucked bad! what would be the best way to get er started up again when it "Deiseling" on me.?

Oh, ya, thanks for the help so far guys! greatley appreciate it!!

A new carb won't clean the carbon from valves or combustion chamber. Using something like "sea foam" or other cleaning products will help. But that is not your problem. And the problem sounds too eratic for just a carb issue. Carbs can run bad, but they don't usually change from good to bad randomly back and forth. Give that distributor a good check.

As for getting it started when acting up. Try pushing the throttle to the floor to give it a good splash of gas. Then hold the throttle half way down. It may take 15 seconds or more of cranking like this but should fire up.

When mine had the same issue. It acted like that for several months. Then it progressed into an accerleration issue. Sometimes it would feel strong and others it would just feel gutless.

sorry to be so clueless but fuel in the bowl means?
Fuel IN the carburetor; so that the accelerator pump squirts when you whack the throttle open. You'll SEE the fuel squirt into the front two venturis if you take off the air cleaner and open the choke.

heh and anywhere I can find out how to adjust the choke on a edelbrock ?
The "official" procedure is available on the Edelbrock web site; the "unofficial" procedure is written and waiting for Al's (website owner's) final approval--if approved, it'll be posted on the Tech Reference section of this site.

what would help with having too much carbon in the chamber?
FIRST, you'd assure that the carb isn't too rich for whatever reason.

SECOND, you'd assure that the ignition system worked correctly,

THIRD, you'd run the engine at fast idle and drizzle a "urine stream" of water back and forth down each primary carb barrel; the water flashes to steam in the cylinder and does a WONDERFUL job of cleaning the carbon out. If you do this right--not too much water at one time--the engine will run SLIGHTLY rough but will not have a dead misfire. No harsh chemicals, no billowing clouds of poisonous exhaust smoke. Just be sure to change oil afterwards; 'cause you'll probably have a lot of moisture in the crank case!

Some folks figure that a quart of water is enough; but I say more is better. I use a garden hose and nozzle set up to just "mist" the water; and I probably put a couple of gallons into the carb over the course of ten or fifteen minutes.

would buying a new carb do? I would rather try anything else besides buying one but If I was force to then I guess I will.
Good attitude. Fix what you have before giving up and throwing money at it.

(I'm still betting on a too-fast idle speed...)

After trying a fuel cleaner like Chemtools B-12 or Cheveron Techron. If that does not clean the extra carbon. Pull out that ol timing light and reset or check yoour timing to make sure you do not have any timing issues.

I had a 67 deville. After I did a slight tune up (wires, plugs, cap, rotor, etc....) When I turned the car on and drive it, everything was kosher. When I would get to the grocery store, and turn the car off, put put, rat rat, put put. It would keep going. I had to use the old school way of putting the car in drive and turn the key off. When I did that, there was no dieseling. I called my buddy(old school guy) and he came to the house with the timing light. We set the timing, moved the distributor, and BAM that fixed it. The timing was off.:thumbsup:

Hey Mike, my car does it too. My car is running great with no issues and it still does it. It only happens on hotter days or after being stuck in stop-n-go traffic for a while. It'll "diesel" on for 1-3 secs. Then if I try to start her up withing 10 minutes it'll almost kill the battery. It only happens when then engine water temp gauge says it's well over 200 degrees. Once it cools down or during cooler seasons, I have no probs.

Shouldn't he check the spark plugs ain't fouled before anything?

no, he should verify the timing and idle speed.

no, he should verify the timing and idle speed.
Just making the point that he should be checking points and plugs before sqirting water down the carb! Cmon guys.

Just making the point that he should be checking points and plugs before sqirting water down the carb! Cmon guys.
You have a valid point, to check the plugs, but plugs alone don't usually keep your car running excessivily after you turn it off. It is usually the timing. I agree with Tom and all the other guys saying check the timing. My prob was timing was off. After we reset the timing, all of the dieseling stopped.

Aye, You all have helped me alot. If feels good to know Im not alone with this problem.

As always when on here, I appreciate everyones help with this and I will def check out those issues.

Mine's been doing this so far this year also. My idle speed is certainly high, my converter seems to lug it down when I put it in gear and the high idle is a necessity right now. Last year it did it a little bit, but I've made a few changes that seemed to bring it back, including the higher idle speed.

Can anyone explain WHY the higher idle speed does it?

Mine's been doing this so far this year also. My idle speed is certainly high, my converter seems to lug it down when I put it in gear and the high idle is a necessity right now. Last year it did it a little bit, but I've made a few changes that seemed to bring it back, including the higher idle speed.

Can anyone explain WHY the higher idle speed does it?
Throttle open far enough to allow plenty of air and fuel into the cylinders; and the piston is moving fast enough to provide lots of compression--and lots of flywheel inertia from the spinning rotating assembly. Ka-Bam! Spontaneous combustion which--even if it's not on all cylinders--continues because of the higher rotating energy.

Lower idle speed reduces amount of charge in the cylinder (greater throttling.)
Lower idle speed reduces piston speed which can reduce compression pressure.

Both together result in lower cylinder pressure; and less likelyhood of run-on.