The idle speed dropped today and it keeps cutting out which is a pain as it's auto! It will sit there and run fine out of gear - but in gear it cuts our randomly at low revs (once going though is as normal)
I had a root around and can't see anything obvious to adjust it - anyone got any pointers?
TIA!
Rather than adjusting to the fault the fault should be found and corrected. The motor is "hunting" for its ideal air / fuel ratio but failing.
I'd look for a small vacuum leak between the mass air meter and the intake manifold - a loose or cracked boot - or a cracked or disconnected vacuum hose. Such a leak of unmetered air introduces a variable that confuses the motor's control system.
I would suspect the MAF... a failing MAF would not allow the engine to idle properly.
-->> T.G. Lambach wibbled:
I'll go have a root around - thanks!
Tiger wibbled:
Please excuse the ignorance - what's a MAF?
Cheers
Mass Air Flow Meter... it is that thing right after your airbox (where the air filter is). When this thing goes bad, idling problems, weak power, plugs may or may not foul out, O2 snesor errors, etc.
These thing does go bad.
Tiger wibbled:
Thanks for that - you beat me to it - should have googled for it in the first place!
New one sitting in the back of the car awaiting fitment in the morning
- GBP£72 - Merc wanted @ £460 + tax (17.5%) - I can only assume it's got a titanium case -but it did come with some 'hoses'!
Much appreciated
I agree with both Tom and Tiger, i.e. air mixture problem caused either by MAF or leakage. It could also be Oxygen Sensor (right, Tom and Tiger?).
Anyway, idle is not adjustable. It is adjusted by ECU, which controls the throttle by a servo cicuit on throttle body.
I'm only wondering why idle is smooth out of gear but stumbling in gear.
When in gear, the engine vibrates more. So I would look for something sensitive to vibration, which could be in the ignition, injection or as suggested in the vacuum lines to the intake manifold.
Jens wibbled:
Replaced the MAF - the car is going appreciably better but still stutters on occasion - I'll check the lines tommorrow. So many thanks for the recommendation.
As an aside - I thought I had all the necessary tools - but no - Merc's done it to me yet again, this time needing a star screwdriver bit with a hole up the middle. My Mk1 hacksaw came in useful again!
Are there any recommended manuals out there for the W210 series - Haynes in the UK haven't done one as yet.
Oxygen sensors are easy to determine if good or bad. On E320 and most MB 6,
8 and 12 cylinders has 4 ozygen sensors.The front sensors are A and using a scanner, the readings are rapid and all over the map... this is normal. The second sensor is after the cat and these are slow changing as with different throttle level.
When an O2 go bad, the reading is normally reads zero... that is really dead.
When you change these O2 sensor, you must replace in pair... front and back of each cat.
Mercedes Benz publishes W210 service manual on a DVD. This is the best source of information.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.