misfiring and fast idling on w124, 1994 E200

[geoffj]

I've got a progressively developing fault on my W124 estate. It started in the colder weather when at start-up the engine sounded like it was firing on three cylinders for about 10 to seconds, then it would clear itself and run smoothly.
Now the weather has warmed up, the lumpy running at start-up has gone but it has developed a very strong tendency to tick-over at about 1500rpm. Blipping the throttle always brings it back down to a normal 8-900 tickover. Moving the car slowly when manoeuvring is pretty jerky as well. Normal running speeds seem fine.
Does anyone have any suggestions on the likely causes of these symptoms ?

 

[bolide]

My first thought would be a dirty throttle body. If you remove the input rubber hose you can clean the throat & butterfly with brake cleaner. I've had a few bad throttle bodies in the last couple of years so be prepared to replace it

If it's not the throttle body I think the fault will be in the ignition system

Nick Froome

 

[geoffj]

Thanks for your speedy reply.

Is the rubber hose all I need to remove, and do you have any specific recommendations for the brake cleaner product you mentioned ? Is this a spray of some kind ?

Thanks again.