Diieseling problem

[malibu80]

I've been frustrated with a dieseling problem on my 83 Malibu. When the car is turned off, it runs on for a little most of the time. I'm afraid something will break one of these times. This is what I've done to the motor. Prior to a non computer control carb change (229 V6), the motor would diesel once in a while. After a carb change, dieseling more often.
Took out all computer related wiring and sensors. Rerouted all emission hoses to 1980 specs. Set timing a 6' BTDC (runs alot better than the computer controlled carb). I've played around with the timing, run colder plugs, checked my EGR valve and dumped a can of decarbonizer down the intake. I'm out of things to try, other than to take it into a shop.

Thanks in advance

Al

 

[HFX]

I've been frustrated with a dieseling problem on my 83 Malibu. When the car is turned off, it runs on for a little most of the time. I'm afraid something will break one of these times. This is what I've done to the motor. Prior to a non computer control carb change (229 V6), the motor would diesel once in a while. After a carb change, dieseling more often.
Took out all computer related wiring and sensors. Rerouted all emission hoses to 1980 specs. Set timing a 6' BTDC (runs alot better than the computer controlled carb). I've played around with the timing, run colder plugs, checked my EGR valve and dumped a can of decarbonizer down the intake. I'm out of things to try, other than to take it into a shop.

Thanks in advance

Al

On a few friends engines I've worked on that had this problem, I found these could be possible cause in order of probability: #1) Vacuum leaks. #2) Throttle not closing all the way on stop. #3) Overheat where the temperature sensor wasn't showing properly. #4) Really old ford, massive carbon that could only be cleaned by removing the heads.

 

[SBCregal]

carbon buildup will cause this problem as well. run some seafoam or KLEENS engine cleaner (a gm product...get the bottle, not the aerosol)
use either according to the instructions on the bottle and it SHOULD help

expect ALOT of smoke though 🙂

 

[megaladon6]

check the cab tuning and idle speed first. especially since it got worse after a carb change. if the idle is too high the throttle blades won't close fully, and a lean condition causes excessive cylinder temps. also check the throttle cable and braket for proper adjustment and binding.

 

[Uncletruck]

If all else fails, shut the car off with the transmission in drive, then shift to park. It won't diesel doing this. Using higher octane gas also most often eliminates it, but is a costly way to do so.

-UT-