Something Broke!!

[johnflight1]

While doing some heavy acceleration on to the highway,when the trans kicked down it sounded like something broke and now there is a vibration any time that you accelerate untill it gets above 1000rpm. It also does not matter if it is in drive or park neutral. It feels like a very bad miss that goes away above 1000rpm.
So I did a compression check and all is well,I also replaced plugs,cap rotor,and did the upper timing cover seals while I was in there and the timing chain looked good. The bad vibe miss is still there Any Ideas???
This is my 88 300E W124 It never idled good anyway but now its like a cement mixer!

[lsmalley]

Check the drive shaft components. could be center bearing or flex disc. Also check transmission mount

[johnflight1]

Thanx for the info I forgot about the center driveshaft mount I will have to check that also when I go to look at the trans mount and flex disc's. Its weird what ever it is goes away at above idle aprox 1000rpm

[pawoSD]

Is this vibration present with engine idling and car sitting in park? Or only when moving? If when moving I would be checking flex discs ASAP.

[johnflight1]

It happens when in neutral (park) also. It will shake till you get to about 1000rpm in neutral or drive

[97 SL320]

Originally Posted by johnflight1

It happens when in neutral (park) also. It will shake till you get to about 1000rpm in neutral or drive

It probably threw a fan blade, have a close look at the center.

Pulling the fan belt and running engine will take the accessories out of the picture.

With engine off, belt off, spin the fan by hand and let is coast to a stop, see if it stops in the same place every time. If it does, the missing blade area will be pointing up.

There is a small change the auto trans flex plate cracked, but they usually just make noise and don't vibe.

[pawoSD]

flex plate could vibrate if a piece broke off and made it unbalanced....but then it should vibrate at all rpms....

[johnflight1]

It smoothes out and runs great after initial acceleration.While searching posts I have seen some posts on motor mounts. Could this be possible that this horrible idle miss could be motor mounts? Anybody have info on testing the mounts to make sure they are shot

[pawoSD]

It would not be motor mounts. A smooth running/idling M103 practically doesn't need them.

Does the engine itself seem to be shaking or vibrating at idle?

[johnflight1]

yep it shakes at idle in neutral and also in gear during initial acceleration.
The car never did idle good.
Once you get past idle around 900 or 1000 rpm it smoothes right out.

[pawoSD]

Shaky idle is probably vacuum leaks or worn out injectors....maybe your high speed run cracked a dried out hose worse or something making a vacuum leak worse. At idle in park and in drive is the economy gauge all the way in the black or nearly all the way when in drive? If its not you have leaks. CIS engines hate leaks and will idle/run poorly until resolved.

[johnflight1]

Just tested and replaced some injectors.I will have a look at the economy gauge on the way home today and will do a check of the vac lines when it cools off

[pawoSD]

The things that like to leak are the CIS airflow meter boot, the idle air lines, and the injector holder O-rings and bushings.

[johnflight1]

While rolling along in drive at idle the econo gauge is pegged in the black till you start to accelerate. We also did a motor mount check in drive and also while in reverse we nailed the gas while holding the brake not much movement in either direction looked ok moved only about an inch or so the engine did not jump out

[pawoSD]

Rolling along in drive is different than sitting still or idling in park. Where is the economy gauge when it is in reverse or drive but sitting still? Where when idling in park?