CLK500 TWINS

Okay, so now that I have full power/ charging and the parasite is gone. Back to the original and only issues I thought I had. Just to recap for those who helped me through the dead phase, bought it with cel on, kid said it needed 02 sensor- cant confirm that. It had a very noticeable vibration in reverse and it idles rough. My tech told me to drive it and let the now fully charged systems throw codes.

Within a couple hours of errand running- still with same symptoms, the cel was back on. I don't have the exact code, but it was "running to rich at idle." He was gone, so one of his guys cleaned my MAF and reset the code. The car felt 10X better, idle only had a slight vibration, vibration in reverse was still noticeable and it drove better as opposed to feeling heavy and sluggish.

By the end of the day the cel was back on and the car seems to be running worse. Now we had a dip in temp here, it's 25 degrees, that might have something to do with it.

It drives okay, but with that heavy feel on acceleration. Idle is boggy, very noticeable vibration in reverse that doesn't smooth out when gear is switched into drive, as it used to. Vibration has intensified to the point where it is causing something in the cabin to rattle.

Based on my own research, MAF needs to be replaced, especially since cleaning it made such a difference, even if it was short lived. It's the second and possible third issue I have here.

Clean throttle body & ICV?
Clogged Exhaust- Possible? how to test for this?
Motor Mounts & Tranny Mount? I feel like this is a strong possibility, but everything I read said motor mounts can cause these terrible vibrations. I have watched the engine as the car was rev'd and the engine doesn't move at all. It also doesn't jump when started. Could this be tranny mounts only?
Harmonic Balancer?
Flex Disc?

I'm sure this list could grow if I keep looking, so I'd rather rely on the experienced opinions I get here. Where do I start and in your opinion, are any of these feasible possibilities.

As always, thanks in advance.

tusabes

Don't throw parts at it . If the maf made a big difference try a new one first , see if it solves the issue

CLK500 TWINS

Yea, I'm definitely going to do the MAF, but even the cleaning of the MAF didn't get rid of the obnoxious vibration in reverse. Could that be from the MAF as well, because even though it was clean, it was still failing?

In addition, do you know if this car can be driven with it disconnected? I saw that some models can and it's sometimes used as a way to confirm the MAF is faulty. Just to make the ride back to the shop less annoying.

CLK500 TWINS

Alright, part took a while to come in, but I got it today and had the new MAF installed. Car ran great, idled smooth, accelerated beautifully, it was really fun to drive for the entire 1/2 hour it took me to get home. Even in reverse, it vibrated some- but not nearly as obnoxious as it had been.

Two hours later, I go start her up and the CEL light is BACK! I drive it hopeful that it'll go off or maybe I'm just seeing things. =( Now it seems to be picking and choosing when it's going to idle rough. One stop light it's smooth, the next it's rough, the next it's moderate. WTH? Acceleration is still good, she doesn't feel sluggish and heavy like she did anymore. I do some shopping, bring her back home.

About 2 hours later I need to run and it feels just as rough as it did post-new-maf. Now this wasn't a long trip, so it may still be a sporadic thing, if I let her run longer it may have been smooth one minute and rough the next.

I need help fellas.

tusabes

You really need to see what the exact cel light code is before we suggest other things
And you may need a scan on a Mercedes SDS computer as a cheap code reader may not give enough detail

CLK500 TWINS

I'll have the code read again, assuming it's the same code as before it was "running to rich at idle." I'll make sure I take note of whatever the current code is.

Welwynnick

I would buy a cheap generic OBD-2 reader before trying to do anything else.


Nick

CLK500 TWINS

I have thought about buying one before, but I'm afraid I don't know too much about them, what's quality vs crap and how to really properly use one. Pretty sure I can figure out the latter though. Any suggestions?

Welwynnick

If its running too rich at idle, you have to find out the cause. It's down to diagnostics. I don't know much about code readers, I just bought one. It won't tell you everything, but its better than nothing. They're so cheap it doesn't matter if you get the wrong one. You're problem could be that the O2 sensors aren't working OK, and that's what OBD2 is really good at.


Nick

CLK500 TWINS

Well I went out and had the code read at an Advance Auto. My guy isn't in on weekends, so I figured knowing something is better than guessing until Monday.

The code it is throwing currently is "P0100 Mass Air Flow Circuit A." So the good news, I guess, is that the new MAF cleared up the "running too rich at idle" which would explain why the car is running better.

Now why is it sporadically reverting back to its post-new MAF roughness and throwing a new CEL code

tusabes

since your still getting a MAF code with a new MAF I suspect there is an air leak in one of the intake hoses , this entire system needs to be sealed

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Welwynnick

Yes it does, but an air leak would tend to cause lean running, rather than rich. And in any case, the ECU would apply compensation to bring it back to stoichiometric.

wallyp

Perhaps an intermittent electrical fault in the MAF Circuit A wire harness or connector, as the code indicates...

CLK500 TWINS

I think those are both very plausible possibilities. I'm no expert, obviously, but I believe I remember reading that if not enough air was getting into the system that it would cause a rich running condition. However; the maf seems to have cured the rich running condition and now it is an issue somewhere else in the system.

Someone somewhere else had mentioned AFR sensors, but that was prior to having the code read and I am not certain that this could still apply.

Googling the code brings you to a lot of faulty maf stories. I read plenty of those yesterday. Googling the term on the other hand brings you to a lot of wiring and connection possibilities.

Friday when it was replaced it went from almost perfect (way home) -to- perfect w/ an occasional rough idle and cel light back on(2 hours later) -to- complete regression (4 hours later, short trip to gas station). The weather here has been mild for winter but humidity and rain have seemingly replaced the normal snow. It had started raining fairly heavy prior to my trip to the gas station. Yesterday it felt great, no noticeable roughness at all - the weather was cool, sunny and dry.

I think I'm going to look at the wiring first, as it would make sense that a frayed or damaged connection would be effected negatively/positively by the amount of moisture that is in the air. At least it makes sense to me, but again- no expert. I know the cowling drain is clear and their is no water in the car because we established that when he hunted down the battery draw. I'll let you fellas know how I make out. As always, thank you!