My car is dieseling (1994 Lumina Z34)

Hello,
I just got the computer replaced because it had gone bad. The mechanic showed me, with the tap test (hitting the computer), the engine would stall out. I told him to go ahead and replace my computer, and everything seemed great. Now, sometimes, if I drive around for a while, my car will diesel for sometimes up to 30 seconds after I take the key out of the ignition. I know this is not good, and the people that replaced my computer said they don't know what it could be. Does anyone have an opinion on the problem? Should I change out my spark plugs? My car has 135 k miles on it.

Thank you.

could the timing be off? Does it run normally well when just driving it? I would say to just give it a week or two to let that new computer "relearn" all its parameters. Wait it out. Good luck

That IS wierd, since dieseling is caused by fuel being ignited by abnormal cylinder temps, coupled with unchecked fuel flow. In theory, a fuel-injected engine shouldn't be able to do it, since the injectors and fuel pump are dead once the key is off, therefore there would be no fuel present to run-on with. I can't even begin to have an answer for this.

maybe try instaed of 87 octane, try 89, or 91, thats what is said to help a carb car keep from dieseling, but, I dont know.

Maybe a leaking injector or injectors? After the key is off pressure will be slowly bled off...but I hooked up a tech2 to my car and disabled the fuel pump, it only ran maybe 5-7 seconds, not nearly 30. Check pump relay, ignition components...hm. That's quite weird.

Was the prom replaced with a new 1 or did they reuse the old prom from the old pcm. I would remove the neg battery cable for about 5 mins then reconnect it and take it for a long drive to help the pcm relearn. The 3.4 is a good engine but hard to work on and you dont want to break the timming chain tensioner by having engine after run

Deiseling?!?!?!? :eek7: How the...
Its a feul injected car, feul injected cars shouldnt deisel...
that is really weird. :eek7:
Thats beyond me. I dont see how it could do that unless there were some serious wiring problems under the dash and hood of that car.