210 idle problems
 

I have a 1997 E420 that has funny idle problems. It seems to be hunting for a steady idle. I have had the throttle body off and rebuilt by BBA and got it back. I reinstalled it but have the same issue with the idle. It has a new fuel filter, fuel pump, ignition modules, air mass sensor, new plugs and spark plug connects, etc.....no codes or check engine light.

Any ideas on what it could be?

Partially blocked cat can do that and cats are problems on the 210.

A nearly-out-of-range O2 sensor might also.

Have you checked the compression?

Have you checked/replaced *every* vacuum line (and "T" or line connector) that connects to the engine?

Hoping they would have looked at that! I took it to MR MB Motors...I will have to call.

Also, check the ERG lines for plugging. A tell-tale is to check the oil filler cap underside for evidence of moisture (ie beige gook).

Would the ASR module have anything to do with the idle problem I am having? The idle seems fluctuate between 1000 and 5000 when car is warm and in the drive position.

Bump!

I still need help. Even the dealer cannot seem to find the problem, they have narrowed it down to the #8 cylinder but don't know anything beyond that.

how can the dealer have the guts to say that they cannot seem to find the problem, they are equipped will all sorts of tools for this brand of vehicle and have technical references to assist them.

Just got off the phone with the stealership and they have moved plugs around and coils around and have narrowed it down to the #8 cylinder....could it have an oil ring for valve problem that would cause the idle to be off?

It only has 158K on it.

Valve yes.. Oil ring. I wouldnt think so. if your valve has something wrong with it, you are not getting the most compression possible, not to mention the gasses would be blown back out the intake or out the exhaust when that piston is on the up-stroke. you should have been able to tell something by the look of the spark plug possibly. but since they fiddle fuddled with them it's hard to say without driving it for awhile and then pulling a known good plug from another cyl and the number 8 and comparing the two.

Got my car back from the stealership. Wow, what a fiasco?? They wanted $150 to move some plugs around and coils around. Then wanted another $150 for a compression test and leak down test. All this after I told them what parts I had replaced. I even talked directly to the service manager. My last experience with them 4 years ago was a $70 oil change and they wanted $4200 worth of work. No wonder I don't take my car there.

So is that the next step...compression and leak down test?

What does a valve job cost? Would I have to do it on both heads or just the side that has a problem (#8)?

You really should find an independent shop....One that is Proficient with Mercedes and particularly your car model... They don't call them stealerships for nothing. As for the Compression/Leak-down you can do this as a DIY if you are handy. Testers are pretty cheap and even cheaper from Harbor freight. As for the valves... I dont know, I would do them both if it was me, Balance and both sides wearing the same would be the benefits of that, I dont know if you can do just one side or even just the one cyl. it's more of 'While you are here, you might as well' sort of thing..

Yeah, thanks. I will have to take it back to MR MB Motors again. Your are right I could do it as a DIY but I work in Las Vegas and it is my wife car (San Diego) with a 2 hour drive to LA to drop it off....etc...all about logistics.

ah. Too bad teleporters dont exist yet...