300ce-24 M104 with a misfire

[grober]

The alarms at that time usually disabled the fuel pump relay and the OVP relay supplies to immobilise the car via their own alarm relays. IF you can trace the non MB alarm wires back to the alarm unit then you can simply bridge them to restore fuel pump and OVP relay function no matter what the alarm state is.

 

[tvr tommy]

I found a blown fuse tucked under the main fuse box, which is taking a live feed so I'll replace that in the morning. Think it should sort the problem, as the sigma alarm is completely dead. Hopefully once all the faults are fixed I’ll have a nice car fingers crossed.

 

[tvr tommy]

Right I managed to get the car going again. The reason for it blowing fuses was there was a short over two wires on the alarm. I took it to the garage and they had a look but couldn't run the Bosch diagnostics on the car as it was to old or something like that. They did fiddle with it but they where doing most the things that I've already done. So I've now got it back and it does run a little better. They did say they taped the end of the HT leads up (spark plug side) as they where arking on the head. I'm not shore if this is true or not. And they also diagnosed a weak spark on cylinder 2 and 4 which I already knew. I think I need to get hold of a scope and see what firing signal the EZL is giving out. As if it's a weak signal for those two cylinders that could be the problem.

I also read that the spark plugs have to be non-resistance and copper cored. I have NKG fitted at the moment and they've done 1000miles these are BCP5ES which a lot of sites say are okay on the M104 engine as they are copper cored and also non-resistance type plugs. But I'm not 100% shore and the wrong plugs will give a misfire.

 

[grober]

Are your plugs gapped correctly. You could also have 2 faulty plugs?? Also logic would dictate that if 2 of your plugs are working correctly then the supply must be OK until its split up by the distributer cap? If you can get it on an old style oscilloscope engine analyser you can watch the individual firing lines for each cylinder and how they vary .

 

[tvr tommy]

I'm just posting so there's a conclusion to this tread.

The piece of plastic behind the rotor arm had some very small cracks in it and the rotor arm was arking on the head behind it. The plastic looked fine until I took it off and there where burn marks on the back. So check that yellow bit of plastic and it may solve your misfire. It's part 17 on the diagram http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=124031&M=104%2E980&GA=722%2E359501&GM=717%2E450&CT=M&cat=520&SID=15&SGR=060&SGN=03

Thanks to anyone who posted.

Tom