240sx Dieseling

[bonestock240sx]

1991 240sx Ka24de
180,xxx miles
170 compression across the board
recently changed spark plugs... they had white deposites on them... consistent on all four. my car has also been dieseling. it seems to drive fine but once i turn it off it almost shuts off then starts back up for about 2 seconds. Then when i go back to start it up it takes about 3-5 seconds to get started. So question is... is it leaking fuel after i shut it off or is it so hot inside the cylinder that it continues running... i looked up dieseling on the forum but for some reason nothing came up like it used to..... so throw some ideas at me

[jbracy7]

check your compression

[sx moneypit]

Does the car ping (spark knock) under acceleration ?

[bonestock240sx]

like i said compression is still pretty good.... and no it doesnt sound like pinging... it seems to run very smooth. it idles slightly high between 1000-1300. ive ran sea foam through as well as amsoil's power foam. both worked for a bit but it came back. amsoil was ran through the intake manifold and the sea foam was ran through the brake booster line. and the fact that my spark plugs were white means im lean which means i probably have a vaccum leak somewhere... correct?

[sx moneypit]

That idle speed is a little high, it may be caused by a vacuum leak. That is probably why the car is dieseling .

[Biggins240sx]

i had the same problem on my car. I had a vacuum leak in the brake booster emission hose

[seang]

If I remember correctly, white deposits on the spark plugs are ash deposits. I'm not sure if that means lean or not, but there are charts all over Google if you want to look at one. NGK has a plug chart.

[bonestock240sx]

yeah it means lean..... im gonna go try and find that vaccum leak right now actually... cus its so simple and is causing so much trouble....

[bonestock240sx]

no luck i didnt find anything. i took off both brake booster lines and inspected them nothing there... and sprayed on all over the intake side with aerosol and still nothing. ideas?

[Biggins240sx]

Im not sure how well aerosol works for checking leaks, since i never used it before. I use silicone spray cause it coats nicely to find leaks. You'll have to check all emission line hoses. also having a stethescope helps. cause then its easier to find leaks, it will amplify the sound of the leak

[motoman399]

check timing, sounds like it could be really far off.

[bonestock240sx]

wow i never really even thought about timing.

[fredward1]

Reviving this thread. I'm having the same problem with little help from the blind world. Any body have a solution.
Stock rb25det
Only 5lbs boost at the moment. I think it's cause In using the stock exhaust for now with 3in down pipe, test pipe.
Wasn't dieseling in the skyline
Idle is high usually but will settle sometimes and be fine. Seems to be random