M119 Intermittent misfire - Defective brand new distributor cap

[tuttebenne]

A couple of months ago I posted what evolved into this thread related to an intermittent misfire and what I was doing to try and resolve it. I have finally resolved it but don't think the solution is best attached to that thread.

How to set up ETA to relearn its home postion | M119 Engine

Long story short, on my 500e I've had a misfire at idle after replacing everything in the ignition (Bosch coils, spark plug wires, Bosch caps, Beru rotors, Bosch insulator discs, correct plugs gapped to 1mm). I did a smoke check and found the vacuum line from the rear of the manifold to the EZL...

www.500eboard.co

The problem began a few weeks after I had installed new Bosch caps, Bosch rotors, and Bosch insulators. At an idle only when hot, there was an intermittent occasional misfire. It wasn't a dead cylinder and it didn't fail all the time. I could go for a drive and not have it happen only to have it fail after a few minutes of warming up the next time I drove the car. On more than one occasion I thought the problem was resolved only to have it come back. Dave and others were very helpful.

Other than the new caps, rotors and insulators the following was performed:
- new plugs
- new coils
- new wires
- new vacuum lines to the EZL and the evaporative system
- cooling system pressure test
- running fuel injector concentrate directly into the fuel rail

At wits end and although the caps and rotors only had 175 miles or so on them, I ordered another set of caps and rotors. After installing the caps the problem appears to be gone. Reinstalling one of the replaced caps, brought the problem back! Finally a solution. Here is what I found. Look at the defect 8mm or so to the left of the rotor contact. Other than that flaw, the cap looks perfect and exactly the same as the others yet it causes the intermittent misfire. I'm in the process of returning it to the vendor for a refund.

 

[gsxr]

Thanks for posting this! Your experience is nearly identical to the problem I had back in 2014 with a brand-new Bosch cap that was defective out of the box. Took me several months and several hundred miles to finally diagnose the problem. Same as your car, it would misfire only at idle, and only when hot. Replacing the new cap (with another new Bosch cap) cured it permanently. I could not see any visual defect in the cap though. I also returned it for warranty replacement.

 

[Trae]

Same here!

 

[J. M. van Swaay]

Same here, only it was a Bosch rotor….

 

[J. M. van Swaay]

Beginning to think Bosch ignition parts for the 119 are s**t.

 

[Joncf]

Beginning to think Bosch ignition parts for the 119 are s**t.

They’re not the best, but definitely not the worst. From what I’ve seen and experienced, Beru is the BEST in regards to quality/reliability. I would certainly use Bosch products over the cheaper options like Bremi, if Beru was NLA.

 

[JAB12]

Thanks for posting.

 

[rayhennig]

I have a Bosch cap that's working but I have my doubts about longevity. It was installed by some cowboys who had my car for a few days in 2019. I cleaned it after about 12 months from new and noted a crack around the centre electrode. Looks suspicious so that'll be replaced when the entire system gets MB originals before winter - plugs, leads, cap, rotor.

So much crap around.

RayH

 

[gsxr]

I have a Bosch cap that's working but I have my doubts about longevity. It was installed by some cowboys who had my car for a few days in 2019. I cleaned it after about 12 months from new and noted a crack around the centre electrode. Looks suspicious so that'll be replaced when the entire system gets MB originals before winter - plugs, leads, cap, rotor.

Note the MB original caps may be nearly identical to the aftermarket Bosch, except with the MB part number on it. The MB original rotors are Doduco and top quality IMO.

I'm not sure if the complete wire sets are still available from MB or not, and may not be worth the cost. MB sells the parts to build your own wire set but it requires a very expensive special crimp tool and many hours of work. Just buy the Beru set described at this link, if your wires are suspect.

Don't forget new insulators, AND to check for any sign of oil or oil vapor leaking from the seals behind the insulator.

 

[rayhennig]

I'm not sure if the complete wire sets are still available from MB or not, and may not be worth the cost. MB sells the parts to build your own wire set but it requires a very expensive special crimp tool and many hours of work. Just buy the Beru set described at this link, if your wires are suspect.

My wire set was made up by MB in Bochum - suppressors and other parts all with MB star. Suppressor cap is the same style as my 1991 originals, like this:


Just looked at the new rotor arm from MB and it's Bosch with the MB star.

Regarding Beru, 10 years ago I should have agreed but my 2019 Beru lead set has been junked in favour of the ancient Beru set that'll soon be replaced by the MB set - not impressed by latest Beru or NGK suppressor caps.

By the way, I was tempted by the crimp tool but 300€ and the team at Bochum persuaded me otherwise.

RayH
PS: All this on an M104.980, by the way.

 

[gsxr]

Interesting... although if your existing plug boots had orange plastic, they were probably not originals from 1991. I've never seen that style used until around 1994-95 on the M119, although I don't know for certain.

OH, wait, this is M104. Nevermind! The M104 is completely different.

 

[rayhennig]

they were probably not originals from 1991.

You may be right as I got the car in 1997 and all but 2 were as above. And yes, M104 but surely not so very different in terms of electrics?

R

 

[gsxr]

You may be right as I got the car in 1997 and all but 2 were as above. And yes, M104 but surely not so very different in terms of electrics?

R

The M104 shares no components with the M119 except possibly the spark plugs. I'm not familiar with the CIS version of the M104 with distributor ignition, and don't know the brands of each component that are OE/OEM. There's a lot of info about the M119 components though, since this is an M119-specific forum.

 

[tuttebenne]

During my troubleshooting I installed a set of Beru wires. They looked every bit as well made as the original MB wires that were coming off at the time. How well/long the actual cable performs; time will tell. As for the M104 and M119 I don't think anything other than a few fasteners is shared between the two. (sux if you are an M104)

 

[rayhennig]

As for the M104 and M119 I don't think anything other than a few fasteners is shared between the two. (sux if you are an M104)

I was thinking more of the technology: distributors, wires, suppressors, etc.

R

 

[gsxr]

I was thinking more of the technology: distributors, wires, suppressors, etc.

R

The secondary side technology is quite similar, although the large cap tends to have less issues than the small cap on the M119.

 

[tuttebenne]

I was thinking more of the technology: distributors, wires, suppressors, etc.

R

M104 has direct fire coils, no distributor, no insulator disc, etc. Three coils for six cylinders. M119 has two distributors, two caps, two rotors, two insulator discs, two coils, for eight cylinders. The M104 has more in common with the M112 and M113 from an ignition perspective. The big difference though is the M112 and M113 have an individual coil for each cylinder, and two plugs per cylinder. I believe one fires on the exhaust stroke to clean up the exhaust; they aren't both firing on the power stroke.

 

[rayhennig]

M104 has direct fire coils, no distributor, no insulator disc, etc.

My M104 has a single coil, one distributor, one insulator disc, 6 leads, 6 suppressors and 6 plugs. M104.98x.

R

 

[tuttebenne]

My M104 has a single coil, one distributor, one insulator disc, 6 leads, 6 suppressors and 6 plugs. M104.98x.

R

Okay. You have the CIS injection on it?

 

[gsxr]

Early M104's had CIS, though USA model year 1992... 1 coil, 6 plug wires, distributor.

Late M104's had HFM, as of USA model year 1993... 3 coils, 3 plugs wires, but no distributor.

 

[rayhennig]

Early M104's had CIS, though USA model year 1992... 1 coil, 6 plug wires, distributor.

Late M104's had HFM, as of USA model year 1993... 3 coils, 3 plugs wires, but no distributor.

Yep.

R

 

[195910]

I switched from a brand new +€360 spark plug wire to a Beru set, as I had issues with the wiring for a whole year!

Conclusion: The most expensive option is not necessary the best.