My 1997 W210 E420 has about 92K miles. The other day the engine started running a little rough during idling and exhibited a little hesitation during acceleration. There was a "engine eletronics" message on the dash. This same problem occured 4 months ago and my mechanic replaced one ignition coil pack at cylinder #5 and that solved the problems. The mechanic said the other 7 coil packs were okay and did not recommend replacement. Is it possible that another ignition coil pack has gone bad and needed replacement? My other questions is how often are we supposed to replace the ignition coil packs and are they expansive?

Thanks, Garry

There is no interval to replace the coils. If they aren't broken, no need to reaplce them. Have the fault codes pulled on the car first to start with the diagnosis of the problem.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

It must be just my luck with this car. The coil pack at cylinder #3 has gone bad and was replaced and she is runnung fine now. This is the second coil replacement in 4 months and I am guessing the typical life span for ignition coils on this engine (M119) must be around 90K miles only.

Garry

How do you diagnose the ignition coils?? My car has about 130k and sometimes is slightly uneven under hard acceleration.

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)

Not sure you can attribute coil pack failure with mileage. Pulled down a number 4 cyl coil pack fault at 124K, my first coil pack failure. Replaced it 4K ago with great results. I'm now experiencing other engine electrical fault problems on an intermittent basis. Recently pulled down P0335 Crankshaft position sensor A Circuit Malf, P0433 EVap Emiss Control Sys Purge Cont Valve Circuit Malf and P0204 Injector Circuit Malf Cyl 4. I cleared them and have driven a week with no repeats.

Some time ago I had a Knock Sensor code. Turned out to be a bad fuel pressure regulator. The engine ran rough at idle with poor top end performance. To check the pressure regulator, pull the small black vacuum line and check for wet fuel residue. If it's wet, it's bad...it was in my case. The reason the knock sensor code came up was due to a greater than 12 degree ignition retard episode...nothing to do with the knock sensor other than, the knock sensor was doing it's job.

Hope this helps

Col B