why does my motor keep running when i shut my truck off

[OlBlue85]

i have a 350 in my truck and when i shut it off it sounds like a diesel truck or tractor and runs for about10 seconds after you shut the truck off< ive took it to 2 different poeple and it still does it sick of getting ripped off any body have any idea what it could be i put new wires plugs distributer and cap timing chain and set the timing and thats what i get still any idea?

[rwhit57]

A few things can cause dieseling as it's called. Timing is one, low grade fuel, and carbon buildup. Try some fuel additive, mess with the timing, and there are a couple of ways to blow out carbon. My favorite is a little trans fluid down the carb keeping the rpms up, then go drive it till the smoke is gone.

[Dalaigh]

I'm going to guess you have an electric choke. Check the wires going to it, if they are fine then chances are the choke has gone bad.

[tucsonjwt]

High idle was my cause. When the truck is dieseling, remove the top of the air cleaner and see if the choke valve is partially closed or if jerking the throttle bracket back quickly stops the problem. You may need an assistant to do this. If you have a stuck choke you can replace your stock choke with a manual choke - I have done this to all my squares and is the best way to make sure your choke is open (or closed) when you want it to be - a $12 experiment. If your throttle is sticking, you will need someone familiar with Q-jets to fix it, unless you can spot the source of the hangup external to the carburetor and fix it yourself.

[bigwheel15]

Check for any vacuum leaks.

[383Chevy]

I had the same problem mine was timing

[BigRed76]

If the centrifugal advance in the distributor gets stuck it will cause the timing to stay advanced causing it to diesel...happened to me.

[kezark31]

ive seen a bad alt cause dieseling as well it back feeds in to the ignition.

[njlimbaugh]

You didn't mention if you had a fast idle solenoid connected to the throttle linkage. These were used on the pre-computer carbs. It's designed to hold the throttle plates slightly open when the ignition is on, but allow them to close completely when the ignition is cut off. If it's not closing all the way, it could be allowing your engine to diesel for a few seconds.

[texasfunk]

Mine was high idle as well at one point

[Dan1969]

Originally Posted by texasfunk

Mine was high idle as well at one point

this

[true74enduro]

vacume could cause it deffinetly. and that wouldnt shock me if all you guys and gals have one and dont know. gm made a mess of vacume lines on my 85 k10 350. ugh my machanic said i can aliminate atleast 99% of you vacume problem with outout effecting the emmisions. becuase basically as long as if you have an 85 and have a cat on it will pass. 84 no need for a cat. ill have to take pictures of all the vacume lines i removed. i could basically supply checker or autozone for years.