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Discussion Starter #1
Hi!

I have a C200 -96.

Yesterday my mom was driving it and all of a sudden the engine started having an erratic idle, lacked power and sounded like a tractor.
I took a look at it just a while ago and first made a compressiontest, all values were good so I checked the ignition with a testinglamp that I put between the plug and the wire.
The plugs from cylinder 2 and 3 did not get any spark, so I tried swapping the wire between cylinder 2 and 4 and there still were no spark. Lastly I swapped the plug between 2 and 4 and still no spark.
It leads me to think there is something wrong with the ignitioncoil, but the weird thing is that two cylinders die at the same.

Any ideas?

Thanks!
 

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Discussion Starter #2
I took a better look at it today after some research on the internet, the car has two ignition coils that give the spark to two cylinders each. Coil nr. 1 fires cylinder #1 and #4 the same time and coil nr. 2 fire cylinders #2 and #3 at the same time.
My problem is cylinder #2 and #3 hence it should be coil #2. I measured the voltage on the LT leads that go on the input side of the coil and they had 10 V when the ignition was on so the LT leads seeme to be working.
I removed the coil from the car and am about to order a new one, i'll keep you posted.
 

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It was not the coil. I got the new one today and it made no change to the engines behaviour, still no spark...

It is really weird because the LT cables show voltage as I turn the ignition on, when the engine is started the LT cables show a varying voltage.

Any ideas?
 

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2008 C200K (W204) & 1998 SL500 (R129) Imperial Red
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Did you replace the spark plugs while you were at it? Could be a bad plug or two..
 

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2008 C200K (W204) & 1998 SL500 (R129) Imperial Red
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3,373 Posts

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2008 C200K (W204) & 1998 SL500 (R129) Imperial Red
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3,373 Posts
Oh, right. My bad. lol I thought coils were used in place of spark plugs. Shows how inexperienced I am. :surrender:
Lol..

Its allgood buddy..

Coils only replaced the distributor. The coils are located right at the spark plugs. Each coil is used to power two cylinders..

So a 4 cylinder vehicle has two coils, while a 6 cylinder vehicle has 3 coils.

I'm no expert on the system, just had some experience with the coils just this week after taking the car to get the engine washed, it started backfiring and idleing rough..

I fixed it as far as I tested, but my one coil could have been damaged and might need to be replaced..will see if the car keeps driving fine..

All the best!
 

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Discussion Starter #9
I tried swapping the plugs between cyl. 1 and 2. I'll try to swap both from cyl. 2 and 3 in case it somehow affects the whole operation of the ignitioncoil if one of the plugs connected to it does not work.
 

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Now I have swapped both the plugs and cables between the cylinders that gets a spark and those who does'nt, it did'nt make any difference.
I found a resistance-table in the haynes manual and measured the coils, plug cables, crankshaft sensor and inlet air temperature sensor and they all seemed fine.

I have the earlier type of coils that is not attached to the plugs, they hang on the underside of the inlet manifold and are quite hard to get to. They both have two low-tension cables going to them and they both have a red/pink cable which seemes to be joined somewhere (both according to haynes cirrcuit diagram and my measurements).
The other cable on the one that fires cyl 1+4(which works) of them is black and on the one that fires cyl 2+3 (does'nt work) is black/white.

I assume nothing is wrong with the red cable because if there were I would'nt get any spark at all. I followed the black and black/white cables to the ECU and then measured the continuity between the ECU plug and the coil, the cables seemed fine (I thought the black/white cable going to the coil pack that fires cyl 2+3 could be broken) they had the same resistance and both had continuity from the ECU-plug.

I also measured the resistance between ground (from cylinderblock) and both of the black and black/white cables going to the coilpacks with the ECU plug connected to the ECU. I found that the resistance was about 550 ohm on the working coilpack and about 770 ohm on the non working.

Could the higher amount of resistance in the LT-cable going to the coil nr 2 (the one connected to plugs in cyl 2+3) lower the current and in that way prevent the spark from firing?

One weird thing occured, I tryed swapping the coils but then I got no spark at all, then I swapped them back and I was back at square one, that is no spark in cyl 2+3. It could probably be due to some cable being put back wrong but I was very carefull and tried to put everything in the right order. Anyhow I thought I should mention it.

So that is what I got so far, anybody got any ideas as to what it could be? Should I just give up on trying to fix it myself? I don't have any ODB2-plug either, it is some kind of round plug in the engine compartment.

I should also mention that a few months ago I changed the headgasket and got the head resurfaced and it worked good until now. I think the injection/ignition/ecu-system is called Bosch PMS, the ECU is Bosch anyhow.
 

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Discussion Starter #11
I have researched the problem on the net and I found several sources stating that the PMS type injection/ignition system has a design flaw in the ECU. There is some transistors in the outputstage that are glued to the board and the gluejoint can fail which in turn makes the transistors melt causing this sort of problem.

I don't know if it is worth spending any more money or time on this car since I recently got a company car but I still would like to get the W202 going because of the amount of time and money I have spent on it under my ownership. It has about 174000 miles on it and could still be sold to someone.
 
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