Does this make any sense?

Mar 21, 2006 9 Replies

Well I towed my car to the mechanic and he looked at the car and started it up and stated that the reason why the car is running for a few minutes and cutting out is because there is a decent amount of gas mixed with the oil. Since I changed the oil last June, he said the rings are probably a little worn and to try letting the oil drain out overnight and put in some 20W50 with a new filter and to just keep on checking the smell from the crankcase to see if ther eis any fuel smell. He said the thicker the oil, the better. I did say that the car was used on a college campus for about



5 months and at times was never really heated up at times. He hooked it up to his testing equipment and said the gas in the oil was making the 02 sensor do some strange things. - Any other input?- Chuck , NJ

On the surface I'd say it doesn't make any sense BUT, its a cheap experiment that's worth trying, if only to humor the mechanic and dispose of as a possibility if it doesn't turn out to be the cause. I'd not expect too much to come of it.

Perhaps most amazing is if this was the problem, why didn't the mechanic just change the oil and filter, instead of telling you to do it overnight? Whatever gas there is in there, most of it has to come out with the oil and I can't see letting it drain for more than say 20 mins, making much difference.

He called me up at first, then twop hours later, i called him up to have him change the oil to a higher viscosity. He was only diagnosing to begin with...

Sounds like another crazy fishing expedition. Might indicate that the stalling is caused by massively over rich mixture?

Well it worked. He said the rings are probably worn and some fuel got in the oil.

| | Sounds like another crazy fishing expedition. Might indicate that the | stalling is caused by massively over rich mixture?

That's allot more likely, and with those symptoms, on any other car I'd be checking the mass airflow sensor first. Not knowing what year 300E that is I cant even tell you if it has one. Is it the Motronic, LH-jetronic or KE-jetronic injection version?

If its the KE jetronic, disregard this. If either of the other 2, its a high possibility and probably just requires the hot wire and pickup cleaning with aerosol circuit board cleaner from any electronics hobby shop. However, intermittent extremely rich running would indicate bad solder joints on the board of the sensor itself.

Sure does make sense.....I am not sure how MB handles this but on a 1992 LT! Corvette with Optispark ignition problems that I had I experienced a similar problem. Once I fixed the Optispark the computer would set a flood state condition and shut down the optispark ignition system due to the fuel vapors in the crankcase from the time it was misfiring. This condition is not documented very well. The flood state condition can be cleared manually, the engine would run for a while and then shut down again. It finally dawned on me what was going on when I checked the oil and got a whiff of gasoline. I promptly changed the oil and this time it ran for almost a minute before it shut down. Changed the oil again and the problem was history. Peter

Of course the mixture is over rich, he stated that he is driving the car only for short distances and not heating it up, which means that the car is runnning on choke all the time. That would lead to an overrich condition right there without any actual problems with the fuel injetion.

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required