Has anyone heard of adjusting the TPS on a 300 CE (88) in order to clean up a rough idle?
I am told this may be my problem but would like more opinions.

THX,

Julian.

Well luckily this IS a yes/no issue. If the throttle switch isn't closed at idle it needs to be. The adjustment isn't easy and is very seldom necessary. Since it's operation is off or on for your model its easy to test.

The reason it matters is that the computor goes to a fixed state in the off idle position. While in the idle position the controller is trying to control idle speed.

Basically I don't think this is the majic bullet here.

There is a very related issue that can play a big part here. That is the accumulation of carbon on the throttle plate and intake valves. The carbon changes the amount of air the idle controller handles. It also absorbs fuel in different quantities varying the mixture on a tightly controlled system.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Steve,
Thanks for your reply.
You say that the sensor is easy to test (since it is off or on). How is this done? I would like to verify all possible options at this point. The car runs well in its initial cold start up but after a short drive the idle RPM drops to just above 500 and the idle is eratic!
I cleaned up the throttle plate and Air intake housing - no results...

Julian.

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Julian.
88 300 CE
82 300 SD