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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3729
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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ML320: , GFs 2002 ml320 with 140k has started idling rough

Customer Question

Hi, GFs 2002 ml320 with 140k has started idling rough sometimes, better and worse, mainly in gear, got a few random misfire codes. Changed spark plugs which looked to be the original NKG "R" with the points on the electrodes burnt all the way down for the bosch 7422/FR8DPP33+ and it helped some but the problem is back, just doing some research.
plan to go over the vac system, clean maf and egr, check hoses including th eone by the fuel filter.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Lou P. master tech replied 1 year ago.
Hello my name is ***** ***** i will do my best to help you , i strive for EXCELLENT service and nothing less. Our coil packs can cause slight misfires. So if a cylinder shows up on the scan tool for a misfire then swap The coil to a cylinder that is not misfiring and see if the code switched also the purge valve can stick open causing a rich condition , or pull the small vacuum line off of the fuel filter and see if fuel comes out. The pressure regulator is internal to the fuel filter and can internally leak causing a rough idle or Stalling condition. Those are all the most common. Also spray around the intake and air filter housing while the neck is connected and see if there are any air leaks. Oh and one more thing lol as if that wasn't enough the egr can stick open slightly causing rough idle and make sure the catalytic converters are solid and don't make noise when hit with a rubber mallet. Sometimes the internals come loose and clog the exhaust , there is not just one common issue as you can see but if you go through my list you will come up with a fix and also brake torque the engine and see how much the engine moved in drive and reverse , you could have s bad motor mount that makes the ML feel
Like it is misfiring. Hope this information helps Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! 😉
Expert:  Lou P. master tech replied 1 year ago.
I have taken my time to answer your question the best i could and i will continue to help if you need follow up information , all i ask is that you PLEASE take a second to rate my service so i may recieve my credit for assisting you. Thank you.

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