akbro93704

hey!
I've noticed that all newer Mercedes models (except the V12's) have a noticeably rough sounding, almost diesel like idle. I've noticed this on some of my family members Mercedes (ML55, E320's, SL500, ML320, CLK320, CLK430,S500...)..has anyone else noticed this and do you know a reason why they sound like this?? Just curious thanks!

vraa

Are you sure? Maybe somethings wrong?

Every Mercedes I've been (various 500's, 55's, and two 600's but one doesn't count because it's RENNteched) have an almost silent idle. The r230 is a little raunchy, sure, but then again it's supposed to be a sports car. The w220 was absolutley silent at around 500rpms I believe. It's almost amazing how smooth these cars are.

akbro93704

ya im sure, as the miles were put on to these engines the idle got noticeable rougher...

BoSoxFan

This may seem like an off-the-wall response but since you are having the same problem on several vehicles: where do you buy your gas? I once had a rough idle on a Porsche and the dealer said, before you bring it in, try a can of injector cleaner since it might be dirty injectors. He recommended a product that was called something like CJ-44K (?). It worked wonders.

akbro93704

Shell or Texaco gas, 91 octane. Before 1999, the DOHC 4-valve per cylinder V8's were very smooth at idle, but once Mercedes introduced the SOHC 3-valve per cylinder V8's, the idle got pretty rough. It could be the engine needs to be cleaned out with what you suggested, I should try it...thanks!!

akbro93704

PS---I think granite grey is an awesome color , kinda irridescent

BoSoxFan

Thanks. I had a hard time deciding between the Pewter Silver and the Granite Grey but I'm really pleased with it. One of the things I really like is that it looks different under different lighting -- sometimes it seems to have some blue in it, other times green, or just grey. I've only had it a month and will put the first coat of wax on it this weekend. I'm curious to see how it shines up.

On the gas, supposedly all the majors use high quality detergents now. However, about 15 years ago, a dealer told me to use only Shell, Mobil, Exxon, and Amoco because of the quality of their detergents. Every time I used a different brand, the engine would run rough.

Another thing: here in the DC area, the daily commute is usually stop-and-go all the way. I would sometimes find that by Friday the car would be rough so I would take it out on the freeway on the weekend and run it at a lower gear than usual to blow all the crap out.

akbro93704

thanks for the info! The engines run great at all other speeds except the idle, so I guess it's not that big of a problem, going on the freeway in a lower gear is a good idea though

Hows the 7-speed in your E-500??Do you know how many MPH is redlines in first gear??I'm curious...thanks!!

BoSoxFan

The 7 speed is awesome. The comfort/sport settings are perfect for city vs highway driving. With all those gear ratios, you never get into one of those situations like when you're doing 10-15 mph and even second gear won't give you the acceleration you need. It's great on the freeway: when you get an opening in traffic, you can shoot ahead without even doing a kickdown. It's still under 1,000 miles so I haven't pushed it to the redline yet. 150 miles to go and then I'll let you know.

RJC

Most of the newer modular engines (MY99+) do have a rough idle when in park or nuetral but not when under load ie in drive. The condition is liked to a lean miss and I'm sure its due to emission concerns. These engines also have much npoisier valve trains compared to the 4valve DOHC previous versions. I'm sure MBtech208 can further enlighten us.

DavidNJ

Unless a mechanical failure is occuring, the only thing that can cause the problem is fuel delivery or ignition.

Check:

Injectors,
Fuel Pump,
fuel filter,
O2 sensor
knock sensor.
iat sensor,
maf/map sensor (I don't know what MB uses),
ignition wires,
plugs (actually, the plugs can go a long way to diagnosing this problem),
coils

It sounds like a knock at no load (diesel sound at idle). Too lean? Faulty info to the ECU? Inaccurate ignition timing?

Is it a hot only or cold only problem?

Remember the ECU is plotting sensor inputs against lookup tables, so if the engine isn't doing what the ECU commands (injectors, fuel filters, fuel pump), or the ECU misunderstands what the engine is telling it (bad sensors), you have a problem.

This isn't a clearence problem, busted cam lobe, bad valve seat or guide, bad lifter, etc.

akbro93704

thanks for all of the info, very helpful!! I don't think I am going to worry about it because the engine's run perfectly, just the idle is a bit crackly...thanks though!!

RJC

Right. As i mentioned it's normal. When I got my first clk 430 in 99 I noticed the same thing and the dealership checked most of what the previous posted recommened. All was normal and I've had 4 new CLK's since my 99 and they all have the lean mis without load on the engine.

akbro93704

ok cool...thanks everyone

akbro93704

RJC---this is a weird coincidence--there's a guy that lives down the street from me, and he has a 2004 CLK500 EXACTLY like yours, and his personalized license plate says "RJC" on it lol

RJC

That's pretty funny. Tell him the initials are copywritten and therefore protected for use on anything related to a clk500 :p

akbro93704

:p sure,ill tell him!!:p

tokomo

Well, if you want to know, I have CLK 320 2000 and you can barely hear the sound of the engine on idle.