Reading many of the serious Engine misfire problems on the Forum, makes mine sound a little pathetic, but worth bringing up. Car is R129 500SL, year 2000, 113 eng. It has a very slight rough idle. Not sure if these engines should be silky smooth... Should I be able to put a Martini on the eng cover and have it not shaken or stirred?? Anyway, I was doing some general trouble shooting - running the car on the drive and I increase the revs, I get to about 4200 rpm and it starts serious hunting and very lumpy. Is a rev limiter kicking in,,, because when normal driving it really flies and will rev to the redline with ease.... pretty impressive. Many thanks for any input.