W124 won't rev above 4000
 

My son replaced the plugs in his 94 E320 and now it acts as if it has a rev limiter at 4000 rpm, it just will not go above that rpm and coughs and sputters and surges until it falls below......Any ideas?

In N or P only ???????????????

It does have a 4k RPM rev limiter if not in gear.

Thanks guys, that was it. Runs fine in drive :eek:

The over-ride speed for this torque converter protection limiter system is 12 MPH.. so an easy test is to go 15/20 mph and then shift to N and the limiter circuit will be void and the rpm will excede the 4K.........this is a system road test only.

Also, advise him to use Bosch F8DC4 copper core plugs with that 104 engine..

Appreciate it! Though I'm thinking the way he drives maybe the rev limiter is not such a bad thing :D

Just a Question..... Why does he want to rev an engine that high or higher without a load on it?