Merc 3.0 dieseling

[70mustang]

I bought a 1999 Maxum with a 3.0 I/O last summer. Most of the time when I shut off the engine it keeps running. I think they call it dieseling. I then turn the key back on and it runs. So I put it in gear and turn it off. This usually shuts it down. Is this a timing thing, a fuel/air mixture thing or just a 3.0 thing? My idle is not high - around 6-700. What is the concensus? Thanks in advance.

 

[jeff13601]

Re: Merc 3.0 dieseling

A lot of times it will do that if your timing is off. Someone said the other night that the motor full of carbon will do it also

 

[Richard Petersen]

Re: Merc 3.0 dieseling

I did. Try cleaning the engine with SEA FOAM from any good auto store. Do it thru the gas tank and to speed the job up. Thru the carb also. Use the amounts they tell you.

 

[kozman01]

Re: Merc 3.0 dieseling

What is your idle rpm? My 04' 3.0 was idling at 1050-100 rpms. The shop dropped it to 650-700 and now I have no dieseling whatsoever.

 

[vipzach]

Re: Merc 3.0 dieseling

The 3.0 is will diesel if the timing is wrong. If your timing isn't off, try switching to higher grade fuel and letting it idle for a minute or two before you turn it off.