ashutt

There appear to be 4 parts that when they go bad on a W208 can cause the car to idle rough or hunt up and down, stall, and eventually die. You most likely will experience a check engine light (CEL). Based on others comments and posts, I have narrowed the possible problems to the following items, though there are certainly others:

(2) Air Mass Sensor
It is possible that the AMS is dirty or bad. You can clean the Air Mass Sensor (Aka Mass Air Flow Meter or MAF) and see if that makes a difference. If it needs to be replaced I can get it from $191.00 at Importecparts.com as well. Install takes about 10 minutes. Do not pay the dealer for the part or to replace this item if you don't have to.

(1) Crankshaft Position Sensor
You may find it hard if not impossible to locate a "Crankshaft Position Sensor" online because it is refered to as a "Reference Sensor". The dealer wants for $125.80.00 or so for this part. I found a site http://www.importeccatalog.com/) that has it for $91.00.

(3) O2 Sensors
These are fairly easy to replace as well. The dealer wants around $225.00 for these parts. You can get them from Importecparts.com for around the prices below:

Oxygen Sensor: Left Front
Located before catalyst
Cost: $155.20

Oxygen Sensor: Right Front
Located before catalyst
Cost: $155.00

Oxygen Sensor: Left Rear
Located after catalyst
Cost: $143.90

Oxygen Sensor: Right Rear
Located after catalyst
Cost: $115.70

(4) Fuel Filter
It appears that you can replace this in about 20 minutes and the part is $32.30 from Importecparts.com.

krayzie_e99

that dam fuel filter took me longer than that, but it was a simple job. my car just hit 100k miles and its a 2000. so the hoses goin into the fuel filter were really stuck on there after loosening the clamps. i had to cut the hoses off and trim them about 1/2 inch. cost me 35 bucks for filter. dealer for sure woulda charged me over 150 for labor and part

Amir_AMG

you forgot the main culprit of rough idle...engine mounts...you can get them for about 60$ each on ebay (there are 2) i got quoted 300$ for parts and labor for both from an indy mechanic...it makes the engine rattle like crazy behind a light...it causes a VERY rough ride...

krayzie_e99

question for u... recently i have been noticing a rough idle. but there is NO check engine light. its a lot more rough when car is on park, when i put it in gear it decreases. the rpm needle doesnt move, its just the car that seems to shake from left to right a little. any suggestions?? by the way,my car has 100k miles

Idle Swede

Spark plugs & wires........

krayzie_e99

i just changed the spark plugs. not sure if u recall, but one of the plugs had broken off. so i had to get the cylinder head removed and machine shop fixed it. they had to rethread it. is it possible they didnt do the job right?

MarcusF

krayzie_e99, do you have the original motor mounts? If so, that may be it.