Rough Idle in gear
 

I have a 1988 300TE with 48,000 miles on it. I have replaced the plugs, plug wires and injectors and still have a rough idle when the car is warmed up and in gear. Anyone have a solution?

I was about to suggest checking the motor mounts but you have pretty low mileage. I thought that 65K on my '91 was low!

Two thing I can suggest:

- Clean the throttle body bore.

- Check the egr valve to make sure the poppet is perfectly seated and no exhaust gases are getting by at idle.

Motor mounts,Motor mounts,Motor mounts must be the mounts

I had moisture in my fuel tank on my 89 300SEL. I used STP gas dry and it cleaned up my problem within a half of a tank. I tried various fixes for my idle, but nothing seemed to help. So I put everything back to factory spec and ran the STP and that fixed my problem.