I have never been able to figure this one out, if my car is shut off at an idle higher then 750, it will diesel everytime. Luckily i have gotten my idle in park to be at 650-700. I know dieseling is helped by high idle, but none of my friends cars do this. Is something wrong with my egr? Perhaps i have too much carbon in my cylinder walls? What would be the diagnosis and repair?

 

check your timing, my NEW 305 (4,000 miles) did the same thing when I got the timing advanced too high trying to get some performance out of it, as soon as I backed it back down to normal it quit doing it.

 

Timing can make it worse--it gets the carbon in the combustion chamber red hot. The fix, get rid of the carbon. Some products exist that can do the job, however I prefer a spray bottle of water. Mist water down into the engine while its running and rev it a little bit to keep in running. It really cleans up the combustion chamber and doesn't hurt anything. If you have carbon build up you will see plenty of black crap coming out of the exhaust when you rev it.