My engine is dieseling when I shut it off. Sometimes it is only for a second and other times it is for 5 or 10 seconds. What causes this and what can I do about it?

 

Mine does the same. Try a higher grade of gas. Also a seafoam to get all the carbon out wouldnt hurt either.

- Excessive carbon build up in heads (hot spots)
- Idle speed too high
- Engine temp too high
- sparkplugs are wrong heat range for car
- bad tank of gas

 

Some common causes are, idle speed too high, running hot, carbon deposits in combustion chamber, and sometimes a good tune up will help.

 

anotrher possible (but unlikely) cause is the carb staying open a bit. spray it with a bit of cleaner if you have it lying around.

if the dieseling happens more sometimes than others, watch if it depends on distance. If longer (and therefore hotter) drives mean longer dieseling then it suggests a problem dependant heat, like carbon buildup (which glows enough to keep fuel burning), pitting cilynder walls, or vaporized oil seeping through the seals and burning. If it isnt dependant on the engine temp its prolly bad gas, plugs, or carb. I know those have been pointing out im just trying to help narrow it down

 

Excellent, thanks for all the suggestions. It does diesel more when it has been a longer trip. I think I am going to pick up a couple of cans of sea foam this payday and see if I can get some of the junk out of there.

 

Tell us how it goes!

 

I haven't tried the sea foam yet but I put a few gallons of premium in it this weekend. Lo and behold, no dieseling. I guess she needs a little better fuel.

 

b/c of the higher octane the gas is more resistant to ignition caused by pressure (which is what causes your dieseling).

but there is still something wrong with the engine