Rough Idle and misfire >4k rpm. 03' ML350
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Newbie
Joined: Sep 2011
Posts: 12
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From: ARLINGTON, VA
ML350
Rough Idle and misfire >4k rpm. 03' ML350
2003 ML350 with about 200k miles.
Changed the waterpump, tensioners and pulleys.
New NGK plugs, Bosch wires and Bosch MAF
I have had the ML for a couple of years. Previous owner had the Cats changed at dealer. I am unsure if the previous owner changed the fuel filter or any O2 sensors.
Running rough at idle in Park, neutral and especially drive.
Idle fluctuates between 650, 700 and 730. Above 1200 rpm truck runs good. Not great. Slight shaking between 15-40mph similar to symptoms that come with center shaft bearing/support. Engine/trans mounts seem OK. No significant movement, clunking or thumping.
Fuel trims bounce around.
STFT bounces between -1.8 and +3.7 on average. Always fluctuating.
LTFT has been pretty consistent at 3.7 and sometimes 0 and as high as 5 while driving it for a while.
Both O2sensor readings before cat bounce back/forth between high/low readings.
I did my best to check for any air leaks and i have cleaned the passenger side valve cover breather/vent. I did also spray throttle body with seafoam spray and have noticed these issues since the pass valve cover service and throttle body spray. Drivers side valve cover breather has not been done yet. I stopped after slightly disturbing the cracked breather hose.
I did also put regular seafoam in the fuel tank. Is it possible that either clogged up my fuel filter and/or injectors? I have a new OEM fuel filter, just seems like alot of work so I wanted to get your opinion on my next move. I have read how to remove IACV/Throttle to clean it correctly. I am just feeling burnt out dealing with this.
I have tried swapping the new wires and plugs with another cyl. with no change. I did the throttle service and seafoam additive after replacing the plugs, but before replacing the wires. I plan to change the plugs again after things are back to normal.
No CEL triggered until above 4k rpm. New Bosch coil on cyl 2. Misfire shows on that cylinder first usually. Sometimes to cyl 5,6 and random multiple if driven hard.
Power steering pulley has faint rattle and shake. I have the replacement pump and pulley, haven't replaced either yet. Prefer to address the misfire/rough idle first. (I am unsure if power steering pump would cause misfire)
Changed the waterpump, tensioners and pulleys.
New NGK plugs, Bosch wires and Bosch MAF
I have had the ML for a couple of years. Previous owner had the Cats changed at dealer. I am unsure if the previous owner changed the fuel filter or any O2 sensors.
Running rough at idle in Park, neutral and especially drive.
Idle fluctuates between 650, 700 and 730. Above 1200 rpm truck runs good. Not great. Slight shaking between 15-40mph similar to symptoms that come with center shaft bearing/support. Engine/trans mounts seem OK. No significant movement, clunking or thumping.
Fuel trims bounce around.
STFT bounces between -1.8 and +3.7 on average. Always fluctuating.
LTFT has been pretty consistent at 3.7 and sometimes 0 and as high as 5 while driving it for a while.
Both O2sensor readings before cat bounce back/forth between high/low readings.
I did my best to check for any air leaks and i have cleaned the passenger side valve cover breather/vent. I did also spray throttle body with seafoam spray and have noticed these issues since the pass valve cover service and throttle body spray. Drivers side valve cover breather has not been done yet. I stopped after slightly disturbing the cracked breather hose.
I did also put regular seafoam in the fuel tank. Is it possible that either clogged up my fuel filter and/or injectors? I have a new OEM fuel filter, just seems like alot of work so I wanted to get your opinion on my next move. I have read how to remove IACV/Throttle to clean it correctly. I am just feeling burnt out dealing with this.
I have tried swapping the new wires and plugs with another cyl. with no change. I did the throttle service and seafoam additive after replacing the plugs, but before replacing the wires. I plan to change the plugs again after things are back to normal.
No CEL triggered until above 4k rpm. New Bosch coil on cyl 2. Misfire shows on that cylinder first usually. Sometimes to cyl 5,6 and random multiple if driven hard.
Power steering pulley has faint rattle and shake. I have the replacement pump and pulley, haven't replaced either yet. Prefer to address the misfire/rough idle first. (I am unsure if power steering pump would cause misfire)
Senior Member
Joined: Dec 2007
Posts: 331
Likes: 51
From: Orange County, CA
'16 Jaguar F-Type R, '21 GLE63s
You will probably get a better response (and more visibility) to your question in the W163 section rather than this one which is dedicated to the ML55 and ML63 AMGs...
