W124 missfire

[dickinsond]

I have become the owner of a 300TE petrol estate with auto transmission, the car has a problem when accelerating. As the car moves off there is a slight missfire which gets worse as the revs approach 3000. This makes gearchanges fierce and if I give the car more throttle it will suddenly surge forward, I can help the gearchange by lifting of the throttle but the car surges as I cruise at 40-50 mph. Also if I engage cruise control the surging is worse. I have changed the plugs which hasn't made any difference and the old ones looked fine all six having the some colour, no fouling or burning. Any suggestions would be appreciated as this is spoiling an otherwise great car.

Dave Dickinson

 

[Bolide]

If the ignition system is OK it must be fuel-related. But I suspect it'll be a bad coil or HT lead or a bad distributor cap or rotor arm

As you put the engine under load it's possible for the spark to "blow out" and cause a misfire

I'd start with the HT system then check the fuel pumps, relay & fuel system

Nick Froome
www.w124.co.uk

 

[DanF]

Hi Dave,

I sorted a possibly similar sounding problem on my 200e recently with a new set of HT leads - an intermittent misfire under load. I'd already recently replaced the plugs, rotor arm and distributor cap so there wasn't much else that hadn't been looked at on the ignition side. I was rather surprised when it worked. BTW Mercedes dealer wanted £30 per lead ?! but bought a set of 5 for about £35 from eurocarparts so not too much damage.

Good luck.

Dan