Son's 1994 E320 won't rev over 4000 rpm
 

This all started after my son had a front end collision and i have replaced all of the damaged parts except for the headlights and the hood and grill
no check engine light no codes where do i start to look

Some things to check
 

With a front end collision, I would check vacuum advance to see if it is functioning properly. Maybe a vacuum line came loose or broke. Possibly another injury to spark advance. Otherwise, check the vacuum and see what it does at 4000 rpm. If it drops like a rock, you probably have back pressure from a plugged exhaust.

Maybe a replaced part was the wrong one for your car? Like an ignition unit for a four cylinder rather than a 6 cylinder, that would limit the revs. Someone more knowledgeable may be able to confirm this.

Gerard

If you are talking 4K lmit in "N" or "P", that is normal torque converter protection rpm limitation. Please specify...

Exactly. I discovered this years ago when I revved the motor while idling in the driveway. Rpm-limited at 4K...

rev limit
 

That could be it wastesting everyting in the shop checking for leaks
i didn't know about the rev limit in park thanks for the info. i thought
someone would know somithing. I still have not put it on the road yet
i will post back to let everyone know

<<That could be it wastesting everyting in the shop >>

Yeah , they have that limit for in the shop cuz they don't want you going more than 75 MPH in the garage ... :):)