M276 intermittent shaking on idle
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Joined: Jul 2019
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c300
M276 intermittent shaking on idle
I know there are big shots here in this forum and I share this issue hoping to get some help from you guys.
2013 c300 4 matic. Since the first month i changed oil several symptoms came up.
1.intermittent shaking on idle. no dashboard code, no OBD2 code, no nothing. idle speed 610 - 630. gas smell on exhaust with not continuous air wave. Monitored the misfire of all 6 cylinders both city and highway, very few occasions 1or 2 misfire counts on cylinder 2 and 4. should be acceptable. purge line has vacuum. oil cap and dipstick seals fine. spark plugs all changed new BOSCH. ignition coils visually checked good.
2.I noticed the long term fuel trim stays high on both banks, especially when idle(-7% - -10%), can reach as low as close to 0 on highway. the highway gas mileage is about 7.8, not bad. but city one is 12, really bad.
3.rattling noise from engine during first minute of cold start . Purchased tensioners and check valves and about to replace it.
4. noticeable shaking on braking on highway from the front wheel somewhere. Once replaced CV boot suggested by mechanics because it leaks like hell. Might due to the play caused by the dry grinding without lubrication.
5.stiff steering wheel and not self centered. alignment feels like ok because no weird sound on highway from tires, no abnormal tire worn , tire pressure normal, power steering fluid at right level, steering pump no whining noise.
6.strange coolant temperature. dashboard gauge shows 90 c, but on OBD2, it fluctuates from 78 or sth to 100 plus on highway, sometimes it even drops during highway drive.
7. strange battery voltage. brand new battery, gives 12.4V with engine off. 11.4V - 14.9V fluctuations with engine on. oftentimes it drops almost 2V from high when accelerate on highway. and last time the mechanic told me the batter is under charge at 70%, but i have drove with it for 3 months by then with many highway drives.
my thoughts will be replace the alternator first and then see if some of other weird stuff will go away by some at least.
Any thoughts from your guys will be highly appreciated.
2013 c300 4 matic. Since the first month i changed oil several symptoms came up.
1.intermittent shaking on idle. no dashboard code, no OBD2 code, no nothing. idle speed 610 - 630. gas smell on exhaust with not continuous air wave. Monitored the misfire of all 6 cylinders both city and highway, very few occasions 1or 2 misfire counts on cylinder 2 and 4. should be acceptable. purge line has vacuum. oil cap and dipstick seals fine. spark plugs all changed new BOSCH. ignition coils visually checked good.
2.I noticed the long term fuel trim stays high on both banks, especially when idle(-7% - -10%), can reach as low as close to 0 on highway. the highway gas mileage is about 7.8, not bad. but city one is 12, really bad.
3.rattling noise from engine during first minute of cold start . Purchased tensioners and check valves and about to replace it.
4. noticeable shaking on braking on highway from the front wheel somewhere. Once replaced CV boot suggested by mechanics because it leaks like hell. Might due to the play caused by the dry grinding without lubrication.
5.stiff steering wheel and not self centered. alignment feels like ok because no weird sound on highway from tires, no abnormal tire worn , tire pressure normal, power steering fluid at right level, steering pump no whining noise.
6.strange coolant temperature. dashboard gauge shows 90 c, but on OBD2, it fluctuates from 78 or sth to 100 plus on highway, sometimes it even drops during highway drive.
7. strange battery voltage. brand new battery, gives 12.4V with engine off. 11.4V - 14.9V fluctuations with engine on. oftentimes it drops almost 2V from high when accelerate on highway. and last time the mechanic told me the batter is under charge at 70%, but i have drove with it for 3 months by then with many highway drives.
my thoughts will be replace the alternator first and then see if some of other weird stuff will go away by some at least.
Any thoughts from your guys will be highly appreciated.
Last edited by tripper80; Aug 7, 2019 at 04:42 PM.
