1992 300ce heavy jerking while maintaing speed.

[mercmike32]

Hey guys,

Sorry if this post is up, I have searched for days now, but no luck finding a problem similiar to mine. Maybe I am using wrong keywords.

Anyways I have a 1992 300ce ~200k miles on it, and speeds above 45 it starts to jerk back and forth very heavily when I maintain a constant speed. If i accelerate or decelerate the car runs smooth. It also does heavy jerking right before 2nd to 3rd shifting (I am assuming it is a transmission issue).
This problem starting happening after I had my car smogged at a local shop.

The "jerking" is, as if someone where to step on the gas pedal quickly and then let go, very rapidly.

I have changed fuel filter maybe 3k miles ago (OES)
New ignition coil (OES)
New cam sensor (OES)
New crank sensor (OES)

Any advice will be greatly appreciated
Thank You.
Mike K.

[mercmike32]

I just took a second look at the car, and it seems to be misfiring even in Neutral when i hold the accelerator at a constant RPM.

Thank You
Mike K.

[Ferdman]

Mike, check the condition of the distributor cap, rotor, sparkplugs and ignition wires. When were they last replaced? What's the brand of the ignition coil? Since you mention the misfiring occurs even with no load on the engine the problem wouldn't appear to be fuel-related ... as in a faulty fuel pump.

[oldsinner111]

I guess it would have no mass to clean,test fuel pressure.There might be a big nut or cap one fuel rail test with air guage should be 55 psi.