hi there im new to this forum.
Ive got a 98 300td merc saloon!!!!!!
Its done 162,000 miles with full history. I!ve been driving it for 2 months and it started running rough once the engine got warm.When slowing down for traffic or stopping.While in traffic the car idles bad and the car shuttered all over the place.Once the car is moving it runs perfect.

So I took it to the mechanics and they said it was the injectors, so I changed all 6!!!!!!!. Picked the car up, it was driving perfect. 2/3 months later its started all over again!!!!!!

Also the car has a bad blow on the exhaust, I think from the down pipe. When still its a little fumey!!!!! So if any one has any ideas to what it could be I would be a very happy bunny many thanks chris!!!!

Air leaks can cause the rough running at idle. I think your year and model have the O-rings/Seals on the Fuel Supply Lines.

The Fuel Pressure Relief/Over Flow Valve can causer rough running at idle.

Check the top of the Fuel Injection Pump to see if it is wet. If so the Delivery Valve Oil Rings are shot; that can also cause rough idle.

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84 300D, 82 Volvo 244Gl Diesel