Budget Baller

So far we've changed the fuel filter, all 12 spark plugs, gaskets, cleaned most of the vacuum lines, cleaned the IMF sensor, cleaned the throttle body changed the air filters, changed the oil and oil filter. What else could it be? Engine mounts are good. Tranny mount, not sure. Idle seems to be more jerky after driving the car hard. Which I don't often do.

The above maintenance definitely seems to have given the car more "oomph" but the rough idle...remains. I thought about kicking it, but decided against it

91RS

Are you sure the motor mounts have been replaced? They don't have to be "blown out" completely to cause th vibration at idle. Replace the trans mount too.

Budget Baller

*sigh* Not sure how easy of a job that is. Tranny mount should be easy. Not sure if it helps, but when the engine isn't under load, it's much better (in neutral) If it was the engine mounts would it not also shake while in neutral?

EDIT to the post above: wires have not been changed.

91RS

No, it will not vibrate in neutral because there is no load on the mounts. It will do it in reverse or drive.

Budget Baller

ah ok thanks. Well I'll order in the mounts and change them anyway but a hunch tells me that's not the issue. (won't hurt to change them) I don't have a hoist so I'm going to probably have to jack up the motor.

The car gets worse when it's warm outside. I can also feel a slight shudder every few seconds (though it's sporadic) It's not horrible but a member in an old thread with a similar issue (though he didn't post if it was resolved or not) explained it as the type of shaking from Jurassic Park ( you know when the water in the glass starts shaking ) That's about what it feels like in terms of extremity. It's frustrating to say the least.

C32vsU

I will preface this by saying I am in know way an expert on cars in general, never mind the C32. I bought my car in november and I immediately starting having similar idle issues, but I also had my car just not start a couple times. I also had some misfire codes thrown. I did plugs and coilovers, and CPS, still didn't fix the problem. I was noticing my coolant light was coming on every two weeks after I filled it. basically I had a faulty intercooler and coolant was being shot into the intake. I am assuming that the coolant was leaking from there onto the plugs and wires thus causing starting issues, rough idling etc.

I too was frustrated when I was looking to the forums on help because you will often see problems posted but no solutions. I think our problems are different, but I can say it sounds like a similar rough idle that I had as well. when the car trembles are you seeing a change in the tach as well? My only two cents is check your coolant level, if it is low then ensure to check under the AMG plenums for coolant build up. If you are have similar problems to my C32 you will have to swap out the intercooler and problem should be solved.

saer1one

I see your point.. Wouldn't he be able to see gunk on the plugs when removing them..? I am with the motor mounts.. had this issue before in the wife's car.. Changed motor and transmission mounts, problem fixed..

C32vsU

That is a good possibility about seeing gunk on the plugs, but I know I had my plugs and wires done first and my garage didn't notice it. Bottom line is that if he is not seeing any loss in coolant the problem is probably not the IC.

saer1one

Agree..

gt4awd

Engine and transmission mount improved the feel of idle on my car A LOT. The transmission mount was dried and cracked. The engine mounts had leaked out. Felt like the engine wanted to jump out and run away...

mgiannetto

There is a thread over on a competing forum where the owner of a C55 claimed to have a similar issue. He was able to solve it by changing his spark plugs and he says "ignition" wires. I'm not sure if he's talking about spark plug wires or the ignition coil wire or both. I'm just quoting what he said. The title to that thread is "C55 soft vibration when idle in gear".

Maybe it's helpful - I don't know, but thought I would throw it out there. Did not see mention of a change of spark plug wires in the list of actions you have taken so far.

Budget Baller

I guess I'm in denial. I REALLY don't wan to change my engine mounts because I know I don't have the right tools, which means it's going to be a PITA. I could take it to the dealer, but I'd rather not. The spark plugs done by the dealer last where all gapped wrong, the tanny fluid should have been changed, it wasn't. (You could tell) and believe or not when changing out the gaskets I found a burnt piece of 3M sand paper underneath the motor about the size of a baseball hat ha ha.

My coolant level is fine and I just had the plenum's off last week. It actually look very good inside for it's age.


I'm wondering though, is there a way to test if your mounts are going out? There must be. Perhaps something to look for visually?

rlddlr53

put your foot on the brake in drive and rev, and in reverse do the same. see if the engine jumps significantly. I believe the left mount is for drive and the right mount is for reverse, could be wrong.


Also when I first got my c32, there was a hose that plugs into the right intake tube after the right air filter housing that was disconnected and fixed this idle problem I had only after the car was warm and driving a bit. ( I did replace my engine mounts as those went bad as well later on)

Budget Baller

Did the test and the engine mounts seem fine. (Both ways) Not much movement. Also checked the hose and it's connected properly.

We also took off the EGR valves and cleaned them along with the hoses hoping it would help. Still nothing. If anything it's a bit worse. I'm really at a loss here.

JonMBZ

MB plugs come pre-gapped how could they have gapped them wrong?

Budget Baller

hmm I didn't know that. When we pulled the plugs they where gapped at around .45 (some where .42 and 2 where .39/40) I was under the impression they needed to be .39. I'm not sure it would make a huge difference but it was something I observed.

Budget Baller

By the way, is there a DIY on changing out the engine mounts?

gt4awd

Jack up the engine, and take off the bolts holding it in place. Thinking a nice calm, and not so windy day would be best... You would be looking around $800 for dealership to do the job and supply the mounts.

Budget Baller

lol thanks GT

Let's hope my brother is down for the job. I know my sister in law is getting sick of us working on the car. What is it with women and "personal time."

gt4awd

Ahh, almost forgot. The dealership unbolts the entire exhaust to clear up some room. Supposedly this might save you a lot of hassle and time.

Budget Baller

Good to know thanks. If it ends up being to much work I'll just take it in and fork out the 900 bucks. Though I'd rather spend that on other toys.

gt4awd

I didn't feel safe jacking up my engine, so yes, I took the price hit. Thinking back the mounts leaking out is probably how the 185MM cut my power steering line. Let the engine sage down some...

Budget Baller

Well I spoke with my brother today and he said it isn't hard, just a PITA. Parts are on their way. Will have them changed out by Wednesday/Thursday. Will post back with the results.

Mark.D

Could be a mis-fire? Sometimes this won't throw codes....

Budget Baller

We had wondered this as well. I took it into a shop today to see what they'd have to say.

They said 2 things. 1 the vibration is due to...bad engine mounts. So everyone here was correct. The slight misfiring feel was from a sensor. I don't have the paper in front of me but I believe he said it was the crank shaft sensor? Don't quote me on that. I'll post back later when I get the paper from the car. He reset it and indeed the weird jerk part of the idle is gone now. Engine mounts will be here Tuesday if Autohaus ships them out on Monday.