continuous engine misfires in a e220 1996

[mike1875]

Hi everyone...m new to this forum somught not b able to be that descriptive.I bought merc e220 petrol w124 1996...the prob frm the very first day is that that cars has very shaking engine.The mounts are ok but on gettin it checked at the workshop i got to knw that these were continuous misfires.Some say get the fuel filter checked..mught b choked..i already got it chkd.But recently a mechanic told me that there is a prob in the actuator(throttle body).The probs are that the car doesnt go beyond 4000 rpm...very low economy(4-5 kms per litre)...needs long self-starts quite often...keeps on shaking at idle due to engine misfire.Pls do guide me...m fed up n choked spending money like water but all in vain..I already got the injectors cleaned and got new three point spark plugs..got all oils changed too..pls help...

 

[Dieselman]

A continuous misfire is likely to be a coil pack, lead or connector. It could be an injector issue, but less likely.

Is it sparking properly?

 

[mike1875]

u mean the spark plug sir??And wat abt the prob of not going beyond 4000 revs...it sometimes used to do earlier..after some peps....but frm abt last 6 days it just isnt ready to do so...

 

[grober]

As Dieselman says- almost certainly coil packs or associated low tension wiring or the engine ECU ignition output transistors. There are specialist rebuilders out there who will repair ECUs on exchange if its that.
ps these engines don't like the 3 electrode plugs best to use the standard copper core NGK's BCP6E's from Halfords. and the HT extenders that go down to the plugs often go faulty internally so best renewed.

pps
if you remove the plugs you should be able to detect which one or two isn't firing. The ones that aren't firing will be dirty. Each coil fires 2 plugs

 

[mike1875]

But bro..wht abt the car not going beyond 4000 rpm and very low economy???pls do put some light on dat too....

 

[grober]

If its only firing on 2 cylinders you are only getting half the fuel burnt to produce energy the rest is going out the exhaust- you are still using fuel but its not being turned into energy. This will possibly limit engine rpms anyway. However if you tested the RPM's while stationary there is a safety rpm cutout to prevent over-reving the car if its not moving.

 

[mike1875]

i tried it both the ways out...it doesnt go beyond 4000,but when i go out for high speed peppy drive..it wont go beyond 4000 for 2-3 tries...but after that it does go upto 6000 easily..but m gettin ur point bro..i'll get it checked..so in other words..does it mean that the throttle body is ok and the prob is in the HT extenders or the coils etc????

 

[grober]

i tried it both the ways out...it doesnt go beyond 4000,but when i go out for high speed peppy drive..it wont go beyond 4000 for 2-3 tries...but after that it does go upto 6000 easily..but m gettin ur point bro..i'll get it checked..so in other words..does it mean that the throttle body is ok and the prob is in the HT extenders or the coils etc????

Don't think a throttle body would cause a misfire- almost certainly HT circuit. I guess its possible the "rev limit" might be down to a malfunctioning throttle body not opening the throttle plate completely. The throttle body has a potentiometer and limit switches built in which tell the injection ECU how wide open the throttle is so I guess this could be faulty. They aren't cheap so your best bet would be to find a substitute one in a breaker,s 'yard. Its just a straight swop but make sure you are getting exactly the same type of unit.

 

[mike1875]

Thanx bro..but usually after three or four peps on a road run it does go beyond 4000 upto 6000.....so wat do i do now?I mean pls do tell me abt the step by step inspection and alteration before i reach a conclusion that its indeed a faulty throttle body(fingers crossed)...mechanics here in india are real thieves..i dnt trust them at all..widout even checkin various things he is straightway sayin its a faulty throttle body and needs a replacement....and if it turns out to be a faulty throttle body..then whr wud i get a replacement(second hand)???

 

[neilrr]

I've seen quite a few W124 E220s which have had HFM ECU problems. It's usually an uncoded unit on a car of this age so if you can find the matching part number it'll be plug & play.

 

[mike1875]

I knw dat..but wud like to be sure abt that before i order one online...wat do i do now?i mean before i reach a conclusion.........???:-(

 

[Algoritmus]

Hi Mike,

I am in middle of an ECU repair (misfire on 2 cyl) and try to replace the ignition output transistors (seems pretty easy so far), so if you interested wait a few days to the result before spend a lot for the ECU as the transsitors cost 6 pounds each

Follow the project on:
http://www.mbclub.co.uk/forums/engine/102590-ecu-ignition-output-transistors.html

Attila