CEL due to misfire - Ignition Coil Test
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Junior Member
Joined: Sep 2018
Posts: 71
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From: Sarnia, CA
2001 ML320
CEL due to misfire - Ignition Coil Test
I started my ml320 without any cranking trouble on one of these cold mornings a few weeks ago and it ran really rough right from the get-go, a puff of medium thick smoke came out of the tailpipe and the CEL stayed on so i decided to take my other car to work. I came home from work, started the ml320 without any trouble and it ran fine even though the CEL stayed on so i started driving it with the CEL on. The CEL went off after about 50 km driving and about 3-5 starts so i put on another 1200 km without triggering the CEL. I bought the ml320 with 155000 km on it and i managed to put on another 96K without replacing the spark plugs, wires or coils. I have no idea when the original owner replaced any of the ignition components.
I figured it's time to do a little tune-up just to make sure that bad mixture and/or un-burnt fuel does not plug up the catalytic converter and what better way than start with changing the spark plugs. I pulled the spark plugs out and they looked fine. I checked the spark plug wires' resistance and they all checked out (2K ohms) except one wire which clocked about 103K ohms. Unfortunately i have not found a retailer who would sell just one spark plug wire similar to this item in europe: https://www.fcpeuro.com/products/mer...ire-0356912948
Anyways, some of the coils look rough but mostly they look fine. Regardless of the visual inspection, i'd like to test the coils to make sure they are within specs. I searched this forum and did not find a procedure how to test coils for the w163. It appears that most people on mbworld pretty much just buy 6 new coils regardless if they are still good or not. However, i am old school. I check all the parts before i replace them... and i dont know how to check these particular coils. I have no idea which pins i should check to find out what the resistance on the primary and secondary windings is.
Frankly, i have no idea why people on here replace all coils just because "it's time" regardless if the coils are good or not. As i am searching this forum, the same goes for MAF sensors on here...replacing them because "it's time" instead of cleaning them first... i am not the type to be replacing parts which are still within spec just because "it's time".... i am hoping these coils are not one of those that have to be checked by an automotive oscilloscope in order to determine their performance, i.e. the output voltage etc. I do not remember if i ever had to replace a coil on my other cars. Coils either work or dont work irrespective of the age or miles; however, none of my other coils were positioned so close to the engine heat and vibrations as the ml320 so this might be different. Regardless, resistance on the primary and secondary windings would be a good indication if the coil is fine our out of spec.
hence my question: does anybody here know how to test w163 ignition coils?
-thank yiou
I figured it's time to do a little tune-up just to make sure that bad mixture and/or un-burnt fuel does not plug up the catalytic converter and what better way than start with changing the spark plugs. I pulled the spark plugs out and they looked fine. I checked the spark plug wires' resistance and they all checked out (2K ohms) except one wire which clocked about 103K ohms. Unfortunately i have not found a retailer who would sell just one spark plug wire similar to this item in europe: https://www.fcpeuro.com/products/mer...ire-0356912948
Anyways, some of the coils look rough but mostly they look fine. Regardless of the visual inspection, i'd like to test the coils to make sure they are within specs. I searched this forum and did not find a procedure how to test coils for the w163. It appears that most people on mbworld pretty much just buy 6 new coils regardless if they are still good or not. However, i am old school. I check all the parts before i replace them... and i dont know how to check these particular coils. I have no idea which pins i should check to find out what the resistance on the primary and secondary windings is.
Frankly, i have no idea why people on here replace all coils just because "it's time" regardless if the coils are good or not. As i am searching this forum, the same goes for MAF sensors on here...replacing them because "it's time" instead of cleaning them first... i am not the type to be replacing parts which are still within spec just because "it's time".... i am hoping these coils are not one of those that have to be checked by an automotive oscilloscope in order to determine their performance, i.e. the output voltage etc. I do not remember if i ever had to replace a coil on my other cars. Coils either work or dont work irrespective of the age or miles; however, none of my other coils were positioned so close to the engine heat and vibrations as the ml320 so this might be different. Regardless, resistance on the primary and secondary windings would be a good indication if the coil is fine our out of spec.
hence my question: does anybody here know how to test w163 ignition coils?
-thank yiou
