SLK 230 1999 wont rev out - massive flat spot any ideas ?

[srdtvr]

My old SLK won't rev past about 4000 rpm for some reason its like theres a rev limiter kicking in and the engine just wheezes - is it the limiter on the cruise control somehow kicking in ?
runs fine otherwise without any issues
Cheers
Steve

[Dog Star]

My old 230 did this once - believe it or not it was the plugs.

[srdtvr]

Interesting - not what I would have suspected but worth a shot
Many Thanks

[r129sl]

My guess is oil on the MAF.

Very, very common on this engine.

It is a result of the crank case ventilation system becoming blocked where at the nozzles below the inlet manifold. You or your man will need to clean the MAF (it may need replacing) and clean out the inlet manifold and pipework.

[Biglips]

^ this. MAF will be the issue.

[srdtvr]

Intersting - MAF was replaced fairly recently but worth checking
I put new pugs and its didnt help ufortunately.
Will check the MAF anyone got a link to a diagram for a MAF on an SLK ?
Thanks for replies Chaps

[r129sl]

You're not reading carefully enough. It is not the MAF that is the cause of the problem. Oil in the intake manifold and piping soils the MAF. The oil gets into the intake manifold because the crankcase breather system blocks. This is the cause. It will happen again and again and again until you clean out the crankcase breather nozzles, no matter how many times you change the MAF. There is an excellent DIY article about this in the Club's online archive (membership circa £40 per annum) but it is not the easiest job in the world.

[srdtvr]

OK Thanks

[srdtvr]

So I've cleaned the MAF sensor and its made no difference - there was a small amount of oil in the tubes not bad though. If it is a blocked crankcase breather do I need to remove the inlet manifold to clean it out?
Would a new MAF sensor be worth a try - are the ebay ones worth a pop or would it be money wasted ?
http://www.ebay.co.uk/itm/260890471488?ssPageName=...
Any info would a great help
steve

[lonny]

My 99 slk had a problem a few years back when I would rev to a certain level - perhaps 3-4000 rpm and would then die off.

I remember the engine dying and coasting to a halt on the hard shoulder of the m1. I gave it a few minutes, started again and all was ok, as long as I stayed under 3-4000rpm when problem would repeat. I took it into my local indie and they hooked it up to the computer and they said it wasn't reading as getting enough air that pointed at the maf. 450gbp late all was well.

If your is bouncing off this restriction then doesn't that point away from maf? Doesn't the super charger kick in around this point as well? Benzworld r170 forums are pretty good for detailed stuff like this.

[srdtvr]

Thanks Lonny - pretty similar symptoms but mine doesnt actually stop running so can drive on after the 4000 rpm dead spot just keep the revs down - it does sound like the MAF is the issue so need to start shopping I think.
cheers

[srdtvr]

So - over the Christmas break I took the inlet manifold off and de-coked the breather jets in the cylinder head inlet tracts which were blocked also the flexible breather tubes were hard and brittle so were replaced at the same time. The pipe work to the MAF sensor all cleaned out and the MAF as well - there was some oily residue in the lower sections of pipes.
All back together and the gears now change when they should and are some how "snappier" but theres still a flat spot if I floor the gas pedal before it picks up its skirts and gets going ?
Any ideas - could this be the MAF or do I need to look at other crankcase breather pipes ?

Cheers
Steve