1987 Mercedes 190 E 4000 rpm shaking

[Thomas G. Kovacs]

Car runs nice below 3000 rpm, although idles a little slow in gear.
In second gear (auto) the car does not rev over 4000 rpm and starts shaking violently at that time. Also in neutral engine can't rev over 4000 and starts shaking. It was just tuned, so it was assumed to be a plugged cat. It wasn't. $200 down the drain and problem is not cured. Can someone help?
Thank you. Tom

 

[television]

Hi Tom, you cant rev a MB past 4k in N as they have built in limiters to cut the fuel supply

 

[Thomas G. Kovacs]

Thank for the reply. But it does not go past 4000 in the first two gears either. Then why have a 6200 redline? Also in gear it idles at a very low 400 rpm, 650 in neautral and the idle speed is not adjustable. Thanks for your quick reply. regards, Tom

 

[television]

Some 190E cars have an idle adjustment under the air filter box, these are the ones without the rotary air valve, if you have a rotary air valve then it could be that at fault.

Have you looked to see if there is a large screw between the block and throttle body just at the front.

OK it should go to max revs in gear

 

[Thomas G. Kovacs]

Hi Malcolm, thank you for your help. Yes there is a screw there but the mechanic tells me that it is for the mixture adjustment and not the idle. Forgive me but what is a rotary air valve and how do I know if I have it? And what is the large screw that you are mentioning? Thanks again, waiting to hear from you, Tom

 

[philhoward]

This might sound like a strange question, but are your sure your rpm readings are correct? It almost sounds as if it is reading at 2/3rds the actual value - unless is really is idling at 400rpm in drive - at which point it would probably stall!

Is it a 4-cyl engine - in which case, could a clock set from a 6-cyl have been fitted at some point? 2/3rds of 6200 is just over 4000rpm...and also your idling speeds would be about right as well.

 

[Thomas G. Kovacs]

I think that you brought up something very interesting. In neutral the warm engine rpm is 650 velvety smooth. When I put it to drive it goes below 500 but does not stall. I thought that the engine sounds somewhat strained between 3-4000 rpm but again this is a big four without balanceshaft. Yes a cluster could have been fitted from a six but a tach is a tach, would it read differently for four and six cilinders? Thank you. Tom

 

[television]

You cant use a 6 cylinder tach from a 4 cylinder car as they work on ignition pulses

 

[Thomas G. Kovacs]

Thank you, it turned out that you were entirely correct. Wrong cluster. Regards, Tom

 

[Bolide]

Excellent catch, Phil Howard!!

Nick Froome
www.w124.co.uk