dacatz

anyone have this experience? i have notice that when car wash machine performing high pressure rinse in the front (grill area), my car will start to rough idle....rpm drop below 500 then stall...when i start the car again....rpm will go above the 500 rpm line a bit..and the needle start going up and down (rough idle)....when i rev the engine once.....everything goes normal again... the only thing i did to the intake is install k&n and remove the extra filter inside the intake box!

it happens to me twice (2 wash) already!

Sheep

This is only a guess, but the high pressure rinse probably created a localize vacuum around the in take, so the engine stall at low rpms. But when you rev the engine, it try to suck more air in and the stall goes away. Just my 2 cents.

Sheep

JL_C63

Same thing happened to me in 2 or 3 washings, i think that the water enter through the intake when existing the high pressure rinse in the front, i suppose that this produce a MAF sensors misreading.

dacatz

make sense

cool....at least i am not the only one.....i thought there is something wrong with my car

Yuille36

Your got it It is rinse water being sucked into the air intake, and the cars MAF sensor trying to make sense of it all. Some water droplets (moisture) is getting past the filter and mixing with fuel and air into the intake stroke. This also happens when driving in heavy rain, but since your foot is is on the throttle at 2500-3000 rpm you don't notice it. But at idle you do. It will not hurt the engine, it is a concern but not a worry. If you really worried about it, contact to local Mercedes shop and talk to a tech.
Its the design of the air intake runners located in the grill, unlike other manufacturers that draw air through the fender well.

Mort

Why not turn the engine off until the wash is done? In the brush-less wash here you just sit and wait for it to finish so may as well turn off the engine and avoid the problem.
The manual also recommends putting the climate control on recirculate to avoid getting water in the cabin filter.

justthebest

Same thing happened to me a couple times. Jut fired it back up and ran it pretty hard to dry everything out.

dacatz

Yuille36

I have not personally experienced this phenomena, but I can see this happening due to the placement of the air intakes.

ZephyrAMG

Water in the intakes and potentially the engine is VERY BAD. We all know that...

Yuille36

yes, this can lead to hydrolock.

dacatz

but little bit of water will create some sort of water injection....and it can remove some carbon deposit inside the valvetrain......