Poor running W123 200 T - advice please!

[Dan the Man]

Hi, was just looking for a few pointers before I get involved with taking the car to bits. I have a 1985 carburated 200 T W123, 105 K. Until this morning it seemed to run fine but is now idling low and appeared to have a missfire at low RPM in traffic.

It has had another curious problem in that although running sweetly, there seemed to be excessive engine movement, allowing the exhaust to knock slightly and giving the feel of poor running when sitting at lights idling. It sounded fine when you lift the bonnet, but engine movement evident.

I'm thinking the two problems may be related and a part is about to pack up somewhere. The car has had a major service including new ignition parts from a main dealer. Engine mounts have been done in the last 18 months. It was also hooked up to some merc diagnostic kit in the summer because I was curious about the engine movement. Nothing undue showed up.

Anyone have any ideas? I thought about a valve on the way out so will do a compression check at the weekend, but have no other thoughts at the moment...

Any assistance would be welcome!

 

[television]

two points to check are the distributor cap for tracking or condensation, and the OVP relay, these can cause poor idle.

Malcolm

 

[Dan the Man]

two points to check are the distributor cap for tracking or condensation, and the OVP relay, these can cause poor idle.

Malcolm

Thank you. It does still run on all cylinders which is odd but will check the cap. Is the OVP relay fitted to non injection cars? Where is it located?

 

[television]

Is the OVP relay fitted to non injection cars? Where is it located?

You do have a good point,i thought about it before i posted,it was shown in the picture here,but not on the list

http://www.detali.ru/cat/oem_mb0.asp?TP=1

I take it that you have cleaned the jets, the choke,main and idle.

Just having taken a phone call,there was one other thing but its gone out of my head,I will come back later in the day

Malcolm

 

[TimN]

Check the HT leads for tracking. Replace the rotor arm as a matter of course if not done in your recent service. Also check any air hoses for splits. If you find and then clean off and seal with electricians tape.