C200 ECU/Miss Fire Issues

[mbraf]

Hey Guys,

Ok where do I start. Well, it might be a good idea to say that im after some help here. Ive had a range of problems so please bare with me as I give you all the details lol

Ive got an Early C200 Auto Elegance I think its a W202 as you people call it. Its on the 1995/1995 plate, just in case its the one with the automatic areil at the back and with the rocking hazard light switch. But anyways,

All of a sudden at the traffic lights in London the car lost all its power, wouldnt do any more than 25-20mph and basically run like a lawn mower. At first I thought it was the MAF sensor however it turned out to be that the car doesnt have one, or it does its just a pressure sensor running from the ECU. But, after getting it towed back home in Wales, and getting a electrician, he proclaimed in was the ECU.

Now at this point it may be useful to tell you that when I first got the car, I noticed that when idle and I rev the engine to about 4k revs it flutters like miss fires. At the time I didnt think much of it as it was running fine. I also had a problem with the Fan coupling where the car was over heating but I also fixed that with a new one of those and a new Rad.

So anyway, after Mr Lekky tested the coils he found the car was running on 2 cylinders. He said that there was no open circuit from the ECU to the coils and therefore it was 99% the ECU.

I sent the ECU away and got it fixed (excellent company). The company sent some instructions saying the following:

"These types of units have often failed due to a problem with wiring between the Ignition Coil and the ECU. THe faulty may not be apparent when the wiring is tested with a multi-meter os even oscilloscope, the main cause of failure is due to the insulation of the trigger wires between the ECU and Ignition coil becoming brittle and shoting to the coil supply wires. THe only way to prove and cure this is to disassemble the wiring loom and trace the full length of wiring for damaged insulation. THe other alternative is to disconnect the related wiring at the ECU and Ignition Coil and run complete new wires"

Well, after doing these checks I couldnt find anything damaged. I installed the ECU started the car, and lone and behold its working fine on 4 cylinders back as normal. However still when I rev it to 4k revs ish it still flutters. Im wondering if this is an indication that the ECU will get damaged again? Obviously im not running it right now.

So now im thinking I will get a brand new cable that goes from the ECU to the coil and change that. If that doesnt make any difference then change the coil itself?

Is everyone in agreement here? Is there anything else that I can do?

thanks

 

[Iain the gadget]

As it's an auto,
the rev limiter is cutting in at 4000rpm to protect from over revving!

 

[mbraf]

Thanks for that. Ive had the idea to put in some new NGK spark plugs, even though when I serviced the car around 6 months ago I put some Denso ones.

I guess I loose nothing with new spark plugs.

How sure are you about the rev limiter theory?

 

[C220GJS]

The rev limiter is not a theory, it is fact, all MB automatics have this limiter to prevent overreving in Neutral or Park.

 

[mbraf]

thank you once again, I just doubled checked its fluttering at 4000 or 40 as it displays on the cluster.

I just phoned the people who repaired my ECU the techy there reconks the limiter is set at round about 6000.

what do you think?

 

[C220GJS]

There are 2 rev limiters in your system , the 4000rpm limit when in N or P , and another which controls the maximum engine revs when in drive , depending on your engine specification this will be set between 6000 and 7000 rpm.

 

[eric242340]

thank you once again, I just doubled checked its fluttering at 4000 or 40 as it displays on the cluster.

I just phoned the people who repaired my ECU the techy there reconks the limiter is set at round about 6000.

what do you think?

Mercedes Benz safety fuel shut off is normally 4000 rpm. When the engine reaches this speed it starts to stall and climbs again. with your foot on the accellerator, in neutral, it will only go to 4000 rpm and then fluctuate between 3500 and 4000 like its surging. ITS NORMAL:wink:

 

[mbraf]

you guys are great and indeed your right

while I was waiting for your much appreciated reply I phoned a Senior tecky in MB who verified all you said.

Just one more thing to go now. As per my first post, this all started when my ECU died. Its all working great now but im trying to make double sure that it wont die again as a result of a surge from the Coil or else where.

Do you guys have any tips on this? anything I can check and so on?

Apparantly its common for the ECU to die in this particular model, have you heard of such a thing?

 

[eric242340]

thank you once again, I just doubled checked its fluttering at 4000 or 40 as it displays on the cluster.

I just phoned the people who repaired my ECU the techy there reconks the limiter is set at round about 6000.

what do you think?

I think they are talking bull sh-t, the safety fuel shut off comes in at 4000 rpm

 

[jberks]

AFAIK - the brittle wiring issue only affected the W124s (same engine). I've not heard of new looms being fitted to W202s.

 

[eric242340]

AFAIK - the brittle wiring issue only affected the W124s (same engine). I've not heard of new looms being fitted to W202s.

I agree with you JB, there are no wiring issues with this model

 

[mbraf]

ok thats cool,

I mean looking at the coils the cable seems absolutly fine.

So let me put it another way. Is it un-heard of that an ECU just goes?

As previously I had heating problems in the car, ended up solving it by a new RAD and Viscous coupling in the mechnical fan. Im thinking that the heat may have affected the coil wiring or indeed the wire that goes from the ECU to the coil packs.

what do you think?

 

[eric242340]

ok thats cool,

I mean looking at the coils the cable seems absolutly fine.

So let me put it another way. Is it un-heard of that an ECU just goes?

As previously I had heating problems in the car, ended up solving it by a new RAD and Viscous coupling in the mechnical fan. Im thinking that the heat may have affected the coil wiring or indeed the wire that goes from the ECU to the coil packs.

what do you think?

Unheard of hey yes.

 

[mbraf]

cool

its turning out to be a good day I just discovered my OVP relay needs changing also. 80 pounds with Merc trying to find a cheaper place to get one

 

[C220GJS]

Try these people; http://www.eurocarparts.co.uk/ ; ovp relay for your car about £45.

 

[jibcl500]

www.eurocarparts.co.uk do them for about half the price.

jib

 

[C220GJS]

No we're not on comission from ECP.

 

[anyweb]

my c220 is a manual, and it too cuts out in neutral at 4000rpm, this is NORMAL and nothing to worry about.

 

[ALAN@ECUCLINIC]

"Unheard of hey yes." umm, hey NO!! i repair pms and hfm units by the shedload. misfiring on 2 cylinders even after the coils have been changed is commonplace hfm also suffer with non start issues too. siemans ecus on a non start generally means its "cattled"

www.ecuclinic.com