ok, confused and a bit aggravated...vibration
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
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.
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.
What's the history on this car?
Cats etc.?
And, BTW: is the transfer case ok; you have a 4M?
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?
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



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
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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.
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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
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.
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 !
Last edited by MwC_Class_S; Oct 27, 2013 at 03:03 AM.
I do need to spend some time doing some more in depth diagnosis.


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.
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.
Dropping it at a shop known for its diagnosing abilities on december 3.
I'm betting its a bad torque converter.
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.
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.
will update as i find out.
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.


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



