I have a beautiful 74 Swinger with low miles I use as my daily runner.

I'm in Southern California and it's been a little warm here recently.

Why is my engine sputtering after I shutoff the ignition when it's been running warm? It may be due for a tuneup, but this happens only when the car has been running warm or hot. I have also started using my A/C, which of course raises the engine temperature.

Bottom line is, it's darn annoying to have the engine stutter/splutter after shutoff and the engine sounds like it's in it's final death throes before it stops. Why is it doing this?

The engine heat is lighting off the fuel with out aid from the spark plugs. This is called "dieseling"

You could have carbon build up on the top of the cyls that is glowing red.

The engine could be running over heated

The idle may be to high.

The idle mix may be to rich.

For sort term you could just turn the car off with it in DRIVE. This will stop it. Once its off then shift in to park and remove the key.

My old ratbox GMC with a 250cui six would "diesel" on forever with the key off untill i dumped the clutch to stop it.

thanks for the advice. Hopefully I can have something done about it. Annoying!!

Actually, too lean a mixture (not too rich) causes or aggravates run-on. So does retarded ignition timing, retarded cam timing, improper spark plugs, poor fuel quality, and the other factors CrALT mentions. It was very common on '70s cars.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

wooo my 77 cherokee did that everytime i shut it off until i checked timming and replaced plugs. but then again there was enough carbon in it to seize a valve, i lost a cyl for about 2 weeks and it came back, ha.
if wutever you do doesnt stop it the shutoff in drive works, as well as holdin foot/floor to gas and flood it out... but then again that thing would start wit a bump of the key no matter wut, unless is was vapor lockin...

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder