1990 2.5 Dieseling Issue

NWI YJ Tyler

New Member
Joined
Nov 15, 2020
Messages
2
Location
Northwest Indiana
Hello, my 90 2.5 is dieseling after shutting down. It will only do it once after turning it off. It has a new Jasper Engines long block and dressings all replaced including water pump, alternator, etc. so I was told it could be a water in fuel/octane issue. Has anyone had these issues or have any suggestions?
 
Some ideas:

Run a carbon-cleaning solvent through your engine. Operate at higher RPM's for awhile. Regardless of its fuel source, a gasoline engine simply cannot diesel without something to ignite the fuel, such as combustion chamber carbon deposits.

Check for correct spark plugs. Replace the spark plugs with "colder" heat range rating.

Change your oil and replace it with a high-mileage full-synthetic. A new Jasper shouldn’t have much oil getting by the piston rings, but I once replaced a Jasper for spark plug oil fouling.

Using a higher octane fuel helps prevent detonation, but it will still diesel.