Just got the car yesterday, very clean with 144K miles and 9 pages of service history in the past couple years. Seemed to run fine. Got a CEL after detailing the car which included an engine detailer (foaming degreaser) that was hosed off with a garden hose and nozzle. Not much water pressure. I have cleaned others with 1500psi washers without issue.

Anyway, ran to the store, couple blocks away, on the way back got into the gas a little and it faltered. When I got home I noticed the check engine light had come on.

Hoping someone has had the misfortune of experiencing this before and I can get away with a reset or maybe not LOL....

TIA

Doug

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6

You probably got water down in the spark plug wells. Pull the fault codes. My guess is that you will find misfires on one or more cylinders.


Don't ask me how I know.

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"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles

OK pulled the code, P0505 Idle Air Control. Any more help? I am searching now.

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1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6

These cars can be really sensitive to getting wet. In my experience, the spark plug boots are likely the cause of a misfire when the engine gets wet. Mine used to do that when it'd get wet, either driving in heavy rain or washing the engine. New plugs and boots seems to have solved it.

Obviously, this has nothing to do with the idle air control motor, just something to be aware of.

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Brian Rogers
'96 E320 traded in at 292,000 miles
'09 C350

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If you were aware of the Electronic Modules in this car, you would not go near it with a hose....
The car is Hot Film Mass with Full Electrnic Sequential Fuel Injection with computer Engine Management.

Would you wash your computer with a garden hose????

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A Dalton

I'm not sure that's a valid point. Cars have to be designed and built with exposure to the elements in mind. If you drive in even moderate rain, the engine is likely to get soaked. If they didn't harden the underhood electronics against water, no one could drive in the rain. Now, a pressure washer may go beyond what they designed it for.

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Brian Rogers
'96 E320 traded in at 292,000 miles
'09 C350

You may be surprised how much thought goes into the placement of underhood-components.
I've had engineers show me & explain why things are where they are.
I was absolutely amazed!
Also, if you open the hood after driving for hours in a torrential downpour, you will see very little actually wet, in the engine compartment.
My car has 2 trays at the bulkhead ( near the bottom of the windshield ), where most of the water, after a carwash, is funneled away.

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2007 C 230 Sport.

Ever see a car come in with electrical problems b/c the owner has taken the lower engine compartment shield off for an oil change and never put it back on..I have many times.. and washing an engine from on top is the same as running the car w/o the bottom encapsulation shield.
..and have you ever seen the cavity that the plugs sit in on the head...pour some water on the top of the engine and that is where it winds up..right on the plug connectors with NO WAY out. , shorting the high tension leads right to ground..the ECU really likes that...
Take my word for it..don't wash these type engine like you used to do to the old Chevy...you are looking for trouble.

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A Dalton

Still no solution. I replaced the plugs even though they looked fine and there was no water at all all in the wells or the boots.

I reset the CEL and while the problem persists, the CEL has not returned.

It must be a sensor or something minor cause the motor will at times pull through the rev range in its typical robust fashion but it is sporadically cutting out and dropping down to approx 900 rpms before it will fire again.

I have one of the scanners that can monitor the car while its running, not sure if any of that info helps and hell if I know what most of it means.

It is idling very high, maybe 1200 rpms.

Definitely needed the plugs though.

__________________
1981 300TD
2005 C55
2004 E500
1999 ML430
1992 400E
1998 C43
2001 SL500
1988 300SEL
1986 190E 16V
1991 190E 2.6