mechanical help needed. my truck is "DIESELING"

[kustombuilder]

it just started all of a sudden yesterday morning when i got to work. on my 83 Chevy truck with the stock 350 4 barrel. i turned off the key and then it just kept chugging and sputtering. i finaly had to put it in gear and turn it off before it would stop. it did it several times last night too. i did look and found one disconnected and a couple cracked vacuum lines but even after fixing those it still does it once in a while. i've also noticed that the idle will be kind of high sometimes and these are the times that it "diesels".

any of you mechanical experts know the cause of this problem. i'm looking for specific answers here, not just "it's your carb". i know how tempting that is for some of you "WISEACRES" out there, afterall, i am your leader http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif.

any help will be greatly appreciated. i have to get a few more miles out of this motor before i can afford the cam, intake and carb i need for my slightly built 350 plus i need to find the time to put that motor together.

thanks...

[skipperman]

Check to see if you have an idle solenoid....should close the throttle plates when the key is off..... if it is not--it'll do just what is happening...also ..... some CHEAP gas can do the same thing...also carbon in the combustion chamber ......and TOO HOT of a plug......

jersey Skip

[G V Gordon]

Check to see if you have a fuel shut off solenoid. If it isn't working properly it will continue to trickle gas into the hot engine.

Another theing that causes it is carbon build up, but since it started all of a sudden I'm betting on fuel.

Looks like Skipperman beat me too it http://www.jalopyjournal.com/ubbthreads/images/graemlins/tongue.gif.

[Fat Hack]

Check your carb...there should be some sort of dashpot that shuts the throttle tight when you turn the key off. If it's not working, that could be your problem.

Also, sloppy throttle shafts, a vacuum leak somewhere or a needle and seat leaking slightly could contribute to that condition.

Common on Q-jet V8s of that vintage, My Monte Carlo SS used to pull that once in a while.

Better gas (higher octane) may help, too...it doesn't ignite as easily.

[BigDdy31]

If it just started, I would suspect the fuel. Did you either just fill it up or are you close to the bitter end of a tank? Maybe bad gas (if just filled) or contiminated fuel (if low or nearly empty).

Maybe not the whole issue but that's where I would start.

Big Daddy Eric

[loudpedal]

The problem is caused by the engine idle being too high when the ignition is turned off. The idle speed adjustment procedure and specifications can be found on the engine placard (it's a sticker), on the radiator support, or on the side of the air cleaner. It sticks in my mind that for an automatic transmission the idle speed spec is something like 750 rpm, manual trans at 650.

If it has happened all at once, check for reasons that would cause the engine idle to be too high; vacuum leaks, floor mat wedged in the accelerator pedal, worn throttle shaft, etc.

I've NEVER seen "bad gas" cause the type of problem you are describing, without causing some driveabilty problems also.

Check it out and let me know if you need any more help.

LP

Chevrolet Master Tech - 16 years

[kustombuilder]

i damn near ran it right out of gas the morning before then went and filled it up. i drove it to work that day then back home and it did'nt do it at all till the day after i filled up. it does'nt take long to go through a tank though so it'll need refillin before the end of the weekend i'm sure. thanks for the other tips too, i'll check into them...


Mike

[tinyelvis]

it's your carb
http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[loudpedal]

[ QUOTE ]

I've NEVER seen "bad gas" cause the type of problem you are describing, without causing some driveabilty problems also.


LP

Chevrolet Master Tech - 16 years

[/ QUOTE ]

If you are not experiencing any driveability problems, it's not the fuel causing your problem.

LP

[CherryBlossom]

[ QUOTE ]
it's your carb
http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

You're such a fag TinyE, good think I love the homo's.... http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/smile.gif