c3 350 Dieseling

[bradmart]

Hi all,

Finally have the old girl on the road in Oz. She used to attract attention on the LV Strip, but driving it in Oz gets more attention than walking through a shopping center naked.

Anyway, can someone explain in a way for the mechanically-inept the concept of dieseling? While 90% of the time, she switches off fine, had an issue once today after coasting down a hill in neutral for about 2 minutes, then switching off at the lights (drawbridge.... 5 minute wait), she didnt want to turn off. Turn the key, and she wouldnt shut down, just spluttering and coughing then refiring. After waiting for another 10 seconds, she shut down fine.

What causes this, and what can be done? The quadrajet needs some finetuning I know, as smells, looks and feels especially rich at idle. Would this be the issue?

Thanks
Brad

[bfit]

 Hi
A good tune up will sort  it out most of the time.

it will not run with  out something to burn  and heat
Some thing in the chamber  is to hot

start  by checking the plugs
while you have them out  have a good look  at them  
they can tell you a lot  about what is going on  in your engine.
 are they clean fouled ?
heat range correct and caped correctly   A starting point  

look up the exhaust and see what colour the  exhaust is
darkish gray is good

 does she use any oil

quadrajet carby. I have never liked them my self
 to many things to go wrong.
Holley carby are much easier to work  with,  its what you are familiar with  I guess.

Post what you find
 

[sirfixalot]

Can also be caused by low octane / crappy fuel

[bfit]

Dame
  I wrote caped  It should have been gaped
fingers and head not working to together
Bob

[gtc]

Agree with the tune up suggestion.

My 454 had a tendency to run-on until the idle speed was lowered.

Also, coke buildup in the heads can provide an unwanted heat source for ignition.