The warm idle speed for my 1989 300TE drops from 700 rpm
to like 550rom when I shift from Park to drive gear.
Have changed the old injectors, new bosch copper plugs, also
cleaned out the idle stabilizer valve and replaced the two loose rubber
hoses that go to the valve.
The car does not die but shakes at such low idle speed.
What could be the possibilities and what should be checked?
Please e-mail me at bshah@satx.rr.com
Thanks for your help.
Barry

I would recommend troubleshooting the EZL (ignition) first. The manual recommends this as well, and I have spent lots of time troubleshooting the CIS when the problem was in the EZL.

I would do a quick pass at the cap, rotor, rotor driver, wires. Run it with a strobe timing light. After this all checks out OK then I would check the Lambda.

__________________
89 300te 222,222
92 300e 190,000

Changing the distributor cap, rotor, wires, plugsm injectors did not fix the idle speed. It appears that 550-650 rpm is within spec for warm idle speed.
But, I grounded the violet wire under the fuse box and it increased my idle speed to 750 rpm at warm.
Barry

Did you have the lambda checked and adjusted with the new injectors? If the engine is running a little lean, it will idle rough but smooth out when you give it gas.

Also, how are your engine mounts? If your mounts are worn, you'll get more engine vibration into the cabin. They usually last ~100k miles, give or take.

Yeah, checked the lamba control and also checked the air fuel mixture.
It checked out.
The idle speed was just too low but mind you, it is within spec.
The car shakes a bit at 550 rpm. The motor mounts are in good shape.
I think if one is stuck in traffic here in San Antonio, TX,and it is quite hot here right now +95-98, it takes a toll on the alternator and battery when
running the A/C, radio etc.at such low RPM.
Anyhow, now my idle speed is at 700-750 in gear.
I think the problem may lie with the hot wire that gets dirty.
Barry