fkong777

I have a 2000 ML55 with 161K mile. For the last 2000 miles, its been running idling rough with hesitations and actually stalled 2 times. It is most noticeable when the AC is on.

It seem to happen after I change oil with Mobil 1 10W-40 high mileage. I have changed the Air Mass sensor, check all vacuum lines. Cleaned out the EGR valve pipe. Still the same.. actually it seem to be getting worse.

Pulled codes from my indy. Stored and Active codes are Air Mass sensor (changed to new Bosch unit) and Secondary air pump. My indy said the secondary air pump will have no effect to the idle and drive quality. it is only use for the starting the engine.

Please give me some insights. Thanks.

davidbho

we're in California...our cars never really get that cold.

It's gotta be one of the sensors. I have 135k miles now, and haven't had this issue, knock on wood.

fkong777

I lived in so cal most of my life. Always hear that oil grade dont matter much in so cal.
I can keep throwing in new sensors. let see. CPS, O2, EGR valve sensor.. I think I will leave it with my Indy.

mihir_d

I am at 146k miles on my 2000 ML320 - had replaced the spark plugs at 100k miles, but decided to extend the coil/wires to 150k mikes. Off late, it has been occasionally hesitating to start - mechanic thinks, ignition coil/wires will solve it

fkong777

Wires and Plugs changed 25K miles ago. just about 1 yr ago.

lkchris

You can't find a 10W-40 Mercedes-approved oil.

Stop looking for numbers like "10W-40" and start looking for "Mercedes 229.5" on the bottle.

gsfent

The only way the oil is causing a problem is if you switched from dino to synth at that mileage.

Good synthetic oil is known to dislodge sludge buildup and that could be affecting the motor. And it could be attacking old seals in the motor if a recent switch. But absent that, I would say any issues are coincidental.

229.5 is the spec, but any good oil in the proper range will do an adequate job in daily driviing.

My personal preference on all my street cars is M1 0w-40, but note that is simply a personal preference.

Regards,
Jerry

fkong777

I just couldnt get it idle one day, now at the shop, Looks like it is the Trottle body. over $1500 for a new part. Indy is going to swap the part with his own and test to see if it is indeed the TB that is having problem.

I wll prob get a bosch compatible or a used part.

idahombz

which indy do you use in So Cal?

fkong777

It was the Throttle body. got a used parts for $250. Run great now. There is no codes for the Throttle Body. It just trip the Maf sensor as the fault which I changed to a new one.

My Indy is M-star automotive in city of industry / la puente.

55fanatic

for future reference the engine oil in SoCal prolly never gets cold enough for you to see the cold weight of oil(0W40 or 10W40 is the same weight when its warm)

having said that, its good to see you got it running again