Rough running CLK - any mechanics in the house?

[SoCalCLKpilot]

I have a 1998 320 CLK that has been running rough for a few months. Basically, at idle it vibrates or shakes. The problem can be very subtle or very noticable. I had been using an independent mechanic (not a Mercedes dealership) here in Southern California. He told me it was the engine mounts. I had him replace them. Or at least I thought I did.

The problem felt like it went away and then it quickly came back, although it does not feel quite as pronounced as before. Then my check engine light came on. I decided to take it to the dealership after my independent mechanic could not give me answers as to why it was still running rough.

I did not tell the local Mercedes dealership about the new engine mounts. They told me the problem causing the check engine light to come on was a leaky air tube of some kind. Great.

But with respect to the annoying vibration at idle, they said that it was the engine mounts. When I told them they had been replaced two months earlier, they were surprised. They said that there was no sign under the vehicle that the engine mounts had been replaced. They even hoisted it up and showed me that the bolts under the car looked undisturbed and the mounts (what you can see with them on the car) looked old. The foreman (head mechanic) thought the engine mounts looked compressed, but could not (or did not) measure them. If they were two months old, they should not have been compressed.

The other possible problem would be the spark plugs and cables, according to Mercedes. This was also what my independent mechanic suggested when I brought the car back.

At this point, I need to decide what to do. Do I replace the plugs, the plugs and cables, or do I pay Mercedes to pull out the old/new engine mounts and see whether my independent mechanic committed fraud and did not really replace the mounts? Either option would be very expensive.

Anyone ever have this vibration problem on their Mercedes? Anyone have any advice? Thanks for any input.

 

[Fightgear]

I suppose its possible the independent got some mounts from a breakers or second hand which might explain the problem otherwise I would suggest telling him that because the vibration still occurs, you took it to a Merc dealership. They said it was the engine mounts and they needed replacing. BUT because you 'know' he had replaced them, you are going to another Merc dealership or mechanic to make sure. If he has conned you then the chances are he will come clean or offer to check them over himself (which will be him replacing them) rather than get caught out.
Changing the spark plugs is not going to harm it and isn't that expensive - it all depends on when they were last changed.
The leads though are not the cheapest of things so it might be worth getting them checked out at an auto-electricians. I think this might be a problem with my car as well but apparently there is a test they can do to check the condition. Best to do that before you spend good money.

 

[GSM1]

Hi, it sounds a bit similar to what I was experiencing, but there are better qualified people on here to advise you.
My garage changed the plugs which cured about 50% of the problem,it wasn't until they changed the leads that it was 100%.
Although they changed the MAF 1st and that had no effect.
best of luck.
Gary

 

[SoCalCLKpilot]

So the plugs and leads can...

cause such a problem. And Fightgear, there is a test you can do on the leads? Is this with a simple multimeter? Is there a test I can name for the dealership mechanic? Amazing that they cannot narrow the problem down between two very different problems.

The dealership is telling me that it would cost about $1,000 US to replace the plugs and leads. Wow! Is that about right? I am wondering if I can just buy them and disconnect the battery and install them myself if I decide to go that route! I have no experience working on a modern machine such as our autos. Don't know if the computer is very accepting of people messing with the electrics.

 

[jberks]

Does the egine shake at idle? Dodgy mounts or not, the idle should smooth and even. If it's not, then its one of the other items. Clearly, without trial and error replacement its going to hard to tell, but my experience is that I have had 2 ocurrences of rough idle on the v6 and cured it on both occasions with a new set of leads. They seemed to have a 3 year life span in my experience. If the plugs have done less than say 50k they are probably ok. The throtlle housing is known to cause poor ilde too, but I'd start with leads.

 

[Fightgear]

Well basically, the leads send a pulse down to the plug which causes the firing. Therefore there must be a fiarly easy way to pick up the value of that impulse. My car is an older 300CE but my roung start and power problem were suggested to be HT leads - because they are just a lead, then I can't see why an auto-electrician or if someone here has the method, a multi-meter way of testing the integrity of the leads. As for the plugs, try this link http://www.drivewire.com/mercedesparts/catalog/mercedesslksparkplug.html.

The leads for my 300CE 24 are about £65 (equiv $100~) so I can't imagine it being massively more unless there is some inbuilt complicated technology!!
Hope its some use!

 

[SoCalCLKpilot]

price of leads

That was 65 pounds for all of the leads? Seems as though $1,000 would be a lot to replace the plugs and leads.

If I could do this cheaply, I would leave the mounts untouched. I still am very curious whether the independent mechanic really did not put in fresh engine mounts - or rebuilt ones. Thanks.

 

[jberks]

Leads from MB are expensive. A full set (remember 2 per cyl so 12 required) set me back over £200. However, there are after mrket suppliers that will be a lot cheaper. Also, a decent idnie should be able to fit some as a test first. My indie fitted a throttle body (£400) and then removed it again when it failed to cure the problem. Thats one of the biggest advantages of an indie though a dealer should really be in a better position to do this.(but they don't)

 

[Uncle Benz]

CLK320 vibration

Have heard talk somewhere of front crankshaft pulley breaking up and causing vibration probs with this engine. Apparently it is of metal/rubber/metal construction and the rubber part has been known to fail. Maybe worth a visual check before spending money.....

 

[MB Novice]

SoCalCLKPilot

I have ther same problem now that you had in 2006 and am wondering what your outcome was. I have had the engine mounts replaced also and now the mechanic says "lets do the plugs and leads" but I notice the other post suggesting it could be the front crankshaft pulley breaking up.

Please let us know what happened with your car.

Thank you

 

[Autofix]

Mercedes ignition parts are expensive so there is no point in changing them unless actually faulty. What you need is to find a man who can read a secondary trace on an oscilloscope and tell 100% if the ignition is at fault. Such a man is likely to be able to tell a lot from exhaust gasses too.

 

[johno2004]

On my CLK320 the idle is rough when in drive or reverse, if you put it in neutral she idles perfect.

I have changed the plugs and still the same am now reluctant to change the leads as why does she idle perfect when not in drive.

Any ideas would be grateful as it is driving me nuts and the indie seems reluctant to find problem as it drives perfect.

Could it be the engine mounts as the engine is under more stress when in drive or reverse.

Any idea's or if there is a member who knows a good mech in leicester who would do a search and fix for me.

Thanks

 

[johno2004]

Any Ideas

Any Ideas please ?