Good evening all,
I'm new to the forum and looking forward to having a good read through.
I have a problem with my 2004 (54) w203 c220 cdi auto saloon. The problem seems to be worse the colder the weather is. Once the engine is up to temperature the bucking goes away and the engine seems to be quite smooth. There are a few things I want to list as possible symptoms.
1. Intermittent fluctuating idle (needle moves +/- 50 rpm) when engine is under load I.e putting car in D with the brake applied.
2. Car bucks quite aggressively when cold (left overnight) between 1400 and 2500ish rpm up to around 80 degrees C
3. If I let the car change automatically when cold it doesn't seem to hold a high rpm before changing gears and changes down to 3rd at a low speed which puts the rpm down to around 1200 and a nasty groaning noise is made from the exhaust/gearbox area. Below and between the front seats.
4. There seems to be no fast idle on cold start it starts at around 900rpm then after a few seconds drops to about 670ish rpm (iirc) although it's been around 2-3c the last few mornings.
5. If I've just been out in the car and leave it for say 2 hours then drive it, the car runs as it should
6. MPG seems a little low at around 37mpg on a 20 mile round trip half of which is motorway travel.
7. Sometimes the engine note changes, usually after say 15-20 miles of driving, the engine becomes very smooth and much quieter than it normally sounds and there seems to be more throttle response.
So far I've replaced the 2 idler pulleys, alternator pulley, belt, new MAF, battery, belt tensioner, one injector, all injectors tested fine and have been cleaned and the injector seats have been cleaned and re cut and stretch bolts and copper washers were replaced and the injectors were coded.
STAR diagnostic showed no faults other than alternator over charging due to a seizing clutch pulley. My mechanic couldn't find any other obvious mechanical faults. Full service was done 5k miles ago (car was doing this before the service). Gearbox has been serviced. I removed and cleaned the EGR valve system but not the EGR cooler (seems hard to get at). New seals on high pressure fuel pump and new fuel lines and fuel return lines. New thermostat and coolant temp sensor.
I did notice the waterpump pulley seems a bit stiff and moves slightly if I wiggle it in and out.
its beginning to baffle me as I've quickly run out of ideas and can't seem to find anything online that relates to my cars symptoms.
Any ideas are welcome. I appreciate you taking the time to read this and I apologise for it not being a short introduction
James.
