Quadcammer

52k miles
new engine mounts, tranny mounts, flex disks, harmonic dampner, plug wires.

The car drives weird. It doesn't feel like the transmission is transmitting 100% of the engine power to the wheels. It doesn't slip per say and the transmission generally shifts fine. There is a pretty wicked vibration through the brake pedal, little bit through the body. Worse when cold, worse when in gear vs. in park.

I'm starting to think its a jacked up torque converter. No obdII codes.

I'm about to head to the dealer for some diagnosis if no one has any other clues. Really ruins the experience of the car.

Any ideas would be great.

Thanks

Quadcammer

I should add the tranny fluid has been flushed within the past 3000 miles with an approved transmission fluid. No signs of coolant contamination.

Plugs have about 15k miles on them and look fine.

The vibration is primarily at idle. Under throttle, it seems fine, but the car does feel a bit lethargic.

kraut56

If you allow me a guess: at 52k miles engine and transmission mounts should be no issue, but: exhaust back pressure could do all kinds of symptoms like that.

What's the history on this car?

Cats etc.?

And, BTW: is the transfer case ok; you have a 4M?

Quadcammer

I've owned it since it came off lease and was still under warranty. I bought it with 26k miles and have owned it for 5.5 years. No major issues since my ownership.

No knocking from the cats, no check engine lights, and generally decent performance.

The only tough part is that I drive less than 2 miles a day (.8 miles to and from the train station)

Since the vibration occurs at idle, I don't think the TC is the cause. It was not part of the recall. There is no strange characteristics at low speed turns.

thanks for your help.

btw, is there anyway besides STAR to read transmission codes?

MB-Dude

Quadcammer - Does the vibration seem worst at ~2,300 RPM? And does it seem worse in 3rd gear? These are my symptoms and the Torque Convertor is highly suspect. Like you, have replaced just about everything else. Just as frustrated.

Kraut56 - interesting thought on exhaust back pressure. Wouldn't OBDII register a fault though, perhaps through the O2 sensors? Any thoughts on how to check/test? I'm willing to explore the possibility if it can be easily done.

Cheers,
Jeff

tusabes

I have a good torque converter for sale

mcguirja

I've been using this tool to monitor fuel trim levels on my SL63. It can give you a sense of when something isn't quite right but not throwing a code yet. The OBDII reader I purchased on Amazon for about $25 and the Torque application was under $5. There are a number of ways to get readings and monitor different systems. I'll try to post one of the videos I've done to give you a sense of how it works. This tool has been well worth it regardless, I've used it for both my S as well as the SL.

mcguirja

When I transferred it to youtube the readings weren't visible unfortunately.

You will also need the track recorder plug in for this to work. In my case I was trying to see what was happening with fuel trims, based on something else that had happened with my SL63. What I was able to see was Bank 1 Long Term Fuel Trim was in the -10% range, which is on the margin, not quite at a point of throwing a code, but not really where it should be. Bank 2 Long Term Fuel Trim was close to 0, which is ideally where it should be. The Torque application allows you to monitor quite a number of systems in real-time, including O2 sensors.

Quadcammer

Jeff,
No to both actually. It really only vibrates at idle or just off idle.

Car idles at between 530-580rpm in gear, between 550-600 in neutral.

exhaust is interesting idea. will have to check that out.

any other ideas are great.

thanks.

MwC_Class_S

Troubleshooting Rule #1 : START WITH THE EASY (& FREE) STUFF FIRST !

Vibrations can be tough to track down, but generally speaking, you need to isolate it to a specific group, ie. Engine, drive-train, wheels & suspension and body/chassis.

If the vibration can be felt when the car is stopped, then it is almost certainly engine related. If the vibration chnages with engine speed as well, then it's a safe bet it's engine related.

Now, one of the most common engine noise/vibration sources is the acessories -fan) belt and tensioner. The good news is that it's fairly easy to to check and just as easy to fix.

TEST: Open hood, remove engine covers. Start engine and listen carefully while an assistant works the throttle, listening closely to the noise/vibration. Now, stop the engine, remove the accessories (fan) belt and re-start the engine. Has the noise chnaged or dissappeared ? Ifso, then you found your smoking gun: one of the accessories and/or the belt is the problem.

Happy Trouble-shooting !

Quadcammer

generally agree with your post. The trouble is that the torque convertor is also spinning with the engine, and at least some of the transmission.

I do need to spend some time doing some more in depth diagnosis.

wallyp

A partially-plugged exhaust normally shows up as a limit on top-end performance, with little or no effect on idle.

You can check for a plugged exhaust by hooking a vacuum gauge to the intake manifold. At idle, you should see somewhere between 16 and 19 inches of vacuum. When you pop the throttle to perhaps 1/4 open and hold it there, the vacuum should momentarily drop to perhaps 10 - 12 inches, and then very quickly climb to 20 - 24 inches and stay there as long as you hold the throttle. If the exhaust is partially plugged, the vacuum should momentarily drop, then climb as above, but will then start slowly dropping as pressure builds in the exhaust system.

groves73

I have the same issue with mine. replaced a bunch of parts and had it in three different shops. Cant figure it out. vibration at idle gets much much better when you turn the ac on. almost goes away and is at same rpm as ac off.

Quadcammer

ok, so I pulled all the plugs. All looked ok.

One wire however had a connector that bent instead of clicking onto the coil. The coil pin was all corroded and the wire connector was screwed. Ordered a new wire and a new coil and hopefully that will fix the problem.

trombone

Did it??

Quadcammer

nope. I reached the end of my diagnostic abilities.

Dropping it at a shop known for its diagnosing abilities on december 3.

I'm betting its a bad torque converter.

trombone

I am sorry you did not yet find the source...
I was also experiencing some vibration recently, very much like the "big dog" growl caused by bad mounts last year, but this time not as strong and certainly did not effect the driving experience. But it came up in the typical range 1500-2000 rpm.
I checked what I could and usually cause the trouble, nothing...
And it was from the AC compressor. Our compressor runs even when we heat the car. Pushing the AC button switches it off but not completely. I pushed the button and the vibration was next to nil...
Switching on the AC again the vibration was back. All I can do to have an AC service, I was told that if the pressure in the compressor is low, the vibration effect is stronger.

Quadcammer

Yup, tried that. Also, below 35 degrees, I think the AC compressor automatically goes to the lowest possible load.

Quadcammer

dropped it off this morning. owner of the shop seems to think its a torque converter or something in the transmission, and I tend to agree.

will update as i find out.

Quadcammer

ok, shop ran diagnostics on it and found everything that is monitored electronically to be operating correctly. They are recommending a compression test as a first step.

I also ordered a new set of Bosch 7422 plugs since I'm gonna be removing plugs anyway for the compression test.

We also discussed the possibility that the corteco harmonic dampner that I installed is not quite right due to the bonding having possibly slipped. It was cheap ($80) and i have to say the casting was crappy compared to OEM. I may buy a new OEM unit (about $200) to see if that will fix the problem.

I'm really guessing the compression test will come out fine, but you never know.

trombone

Good luck Quadcammer.
I would put my money on the harmonic balancer...
And I hope you won't need to spend money for fixing a compression problem...

mb techman

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wallyp

I agree with techman. I taught a "Basic Tune-up" course for years, and one of the suggestions that I made to each class was to try for a short burst of full-throttle acceleration on each drive. After the car was warm, not high RPM, not high speed, not unsafe driving. Easiest way for most folks is full throttle on the entry lane of the Interstate/freeway/highway until you get to merging speed.

Quadcammer

been doing italian tune up as much as i can with seafoam and techron in the tank.

I'm gonna see what the compression and plugs do next week.

thanks guys

mb techman

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