[DONNA U]

I'm new to the forum, and have been reading a lot of helpful tips. Maybe you guys could help me with this one. I've been starting my '99 230 regularly while in winter storage and I've noticed when reved at around 4000 rpm I'm hearing a miss or something. It's always been a little sluggish on cold starts but this "miss" is new. Any ideas what or why this is??? It got it's 30,000 mile check up at the dealer last summer and all was ok then. I'm hoping it's nothing major!!!!


donna u

 

[quest4mike]

Its actually not a good idea to rev the engine without a load. I think mecedes did this on purpose. mine does this and when i drive it drives fine..scary huh? MIke

 

[Bruce R.]

At 4,000rpm it's not a miss, it's the fuel shut off cutting the engine...

If your not in gear, and just sitting in the garage revving the engine, there's no need to go over about 2,000 rpm. The alternator puts out it's peak power at well below 2K and without a load on the engine bad things can happen, so Benz put a limiter on it. There's nothing wrong, drive the car when weather permits.....[][]

 

[Kirill]

I believe i read it here before - in park ECU does that miss around 4000 rpm on purpose - so you wouldn't kill your engine\tyranny.

 

[DONNA U]

Thanks all of you!!! I can't wait to get it on the road..........whenever it stops snowing!!!![]

 

[Bruce R.]

Driving the SLK on the road is usually more fun then sitting behind the wheel, and driving it in your mind. [][][] Things will get better soon.[]

 

[430]

RE: At 4,000rpm it's not a miss, it's the fuel shut off cutting the engine...

Bruce R. - 3/15/2005 10:54 AM

If your not in gear, and just sitting in the garage revving the engine, there's no need to go over about 2,000 rpm. The alternator puts out it's peak power at well below 2K and without a load on the engine bad things can happen, so Benz put a limiter on it. There's nothing wrong, drive the car when weather permits.....[][]

Not that I ever do it, but why is revving in neutral bad? I can make some educated guessesbut...

 

[Bruce R.]

One of the prime reasons is that the bearings are not loaded "properly"...

The rod bearings can flop around (within the tiny parameters that they have), the rod bolts can be over stressed, and it's easy to over rev the engine which can lead to valve float. These are interference engines so valve float cannot be tolerated. With a new, tight engine, it's probably not that big a deal, but once the engine gets a few miles on it and the clearances and tolerances open up, it's easy to overstress assembly bolts.

 

[430]

Thanks Bruce.