M119 engine coughs, stutters, backfires, won't rev

[maplevalleyhammer]

We have acquired my in law 1995 E420 with only 54k on the clock. Several months ago, I changed oil, brake fluid, installed new pads & rotors, replaced 12 year old Michelins, fuel filter and caps/rotors ...car ran great, 23mpg highway. After sitting for about 3 weeks, it made it about 2 miles and started missing then...kerblam! backfire while traveling at about 40mph and did not want to start. Almost seems like carbon tracking that these are known for in distributors. I have not pulled them yet. Any other ideas from the experts on this site?
Thanks, any input greatly appreciated!!
Brian

 

[captruff]

Re: 1995 E420 coughs stutters & backfires

If it ends up being the upper engine harness, I have a late production one available in very good condition.

Jeff

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

Crazy thing to check, but... pull the caps/rotors, and remove the plastic insulators behind the rotor bracket. Inspect the back side for any sign of fluid residue. They should be bone dry. If not, clean then up with something that won't attack plastic, also wipe down the caps/rotors, and re-install. There's [almost] no way new caps & rotors would fail inside a few months.

Otherwise, check for codes, clear/reset and see which codes return. Backfiring sounds awfully ignition-y to me though.

 

[Stevester 500E]

Re: 1995 E420 coughs stutters & backfires

Is this a long shot?
Can after-market caps let more than average amount of moisture enter the caps causing misfiring?

 

[SG-Motorsports]

Re: 1995 E420 coughs stutters & backfires

Is this a long shot?
Can after-market caps let more than average amount of moisture enter the caps causing misfiring?

Yes, the non-genuine Bosch caps are notorious for letting in a ton of moisture, especially in our wet/damp climate here in the PNW. It's always a good idea to replace the o-ring for the plastic insulators whenever you replace caps and rotors.

Maplevalleyhammer, this sounds exactly like what you have going on, even though the caps are brand new. If it backfired and now won't run at all, may want to check your vacuum hoses to be sure one or more didn't blow off with the backfire. It's not very common on M119's, but still very possible.

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Not A longshot at all. Dollars to donuts, Hammer, that's exactly what you have going on.

I will go a long step further: IMO, disintegration of these insulator plates is the second most chronically under-diagnosed condition of the M119 closely following inoperative fan clutches. And also related, as it has always appeared to me that chronic hot running hastens the disintegration of the plates, just as it does for most plastics.

It is my theory that the disintegrating insulator plates are what emit the detrius that is invariably found coating the inside of the caps and the rotors. This coating is either highly attractive to moisture and / or condenses as a fluid itself. Often it will be found in copious quantities between the plates and the cylinder heads. After a clean up, new O-rings may help prevent future reoccurrences, as they may allow a little less moisture entry, if indeed the phenomenon is one of hydrophilia, but note that there are vent slots in the bottom of the caps right at the O-ring interface, so these caps are open to the atmosphere. Not absolutely wide open mind you, but open. And no, additional ventilation alone does not help. In fact, it makes the problem worse.

I have had to address countless cases of chronic cap-itis on the M119. In every case I have been involved with, replacement of the insulator plates stopped the "needs new caps every few weeks to few months" syndrome.

Per Gixxer's comment, yes I have had some excellent luck cleaning, wiping and blowing out these components. Clean rags, CRC "Power Lube" or CRC "5–56" and compressed air can usually eek another year or two out of the plates before they start coating the caps again. If you really like this car and want to keep it a long time, clean your recently replaced caps and rotors in this manner and replace the plates. If you're not sure you're going to keep it, remove the plates, clean them in the same manner and reinstall them. This is also a good test if you are not sure that distributor issues are contributing to your problem. If you do this cleanup and your problem stays away, you can bet this is what's going on. Perhaps at that point, you may want to replace the plates if you're keeping this car...

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Yes, the non-genuine Bosch caps are notorious for letting in a ton of moisture, especially in our wet/damp climate here in the PNW.

Yep, my experience on the central west coast of Florida was identical. Everybody bitched about the Bosch caps, but everything else that I ever had experience with on a M119 was way worse...

 

[emerydc8]

Re: 1995 E420 coughs stutters & backfires

Klink,

I remember you telling me about your theory that these insulators emit some sort of mysterious orange powder as they degrade and this powder can cause latent ignition problems. I went out to the garage and looked at an insulator I had replaced last year. This was from a car that spent its whole life in Southern California and had 200,000 miles on probably the original insulators. Sure enough, just rubbing the insulator with a shop towel caused some of that orange moon dust to come off (pic).

The first picture is the new insulator next to the old.

 

[gerryvz]

Re: 1995 E420 coughs stutters & backfires

Jon,

We have a term for when a part looks like that ... you've heard it when someone says "man, that is really clapped out". When you have worn .036 parts, you'd use the term "man, that distributor cap insulator plate is totally Klinked out!"

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Jon,

We have a term for when a part looks like that ... you've heard it when someone says "man, that is really clapped out". When you have worn .036 parts, you'd use the term "man, that distributor cap insulator plate is totally Klinked out!"

You're correct in reverse, Honch! You can say the motor has been "Klinked" after those plates are dealt with...

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Klink,

I remember you telling me about your theory that these insulators emit some sort of mysterious orange powder as they degrade and this powder can cause latent ignition problems. I went out to the garage and looked at an insulator I had replaced last year. This was from a car that spent its whole life in Southern California and had 200,000 miles on probably the original insulators. Sure enough, just rubbing the insulator with a shop towel caused some of that orange moon dust to come off (pic).

The first picture is the new insulator next to the old.

Yep, you're looking at it. My theory for a long time has been that this substance comes from the plate itself, or at least that the plate itself emits something, and then this "something" attracts and retains the moisture.

 

[gerryvz]

Re: 1995 E420 coughs stutters & backfires

Yep, you're looking at it. My theory for a long time has been that this substance comes from the plate itself, or at least that the plate itself emits something, and then this "something" attracts and retains the moisture.

Klink, there's actually an MBCA article about this plate that I posted a few years back that came out in the club magazine as the issue with some difficult to diagnose M119 running issues. At the time I scanned and posted the article; I know it is somewhere on the site but I'll have to find it again....

 

[8899]

Re: 1995 E420 coughs stutters & backfires

Pretty sure that this is the article:

 

[gerryvz]

Re: 1995 E420 coughs stutters & backfires

Pretty sure that this is the article:

Yes, Greg .. very much that is it. Thank you kindly for re-finding and posting this article in this thread, as it's very relevant.

Man, look at that Klinked-out distributor insulator disc !!!

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Yes, Greg .. very much that is it. Thank you kindly for re-finding and posting this article in this thread, as it's very relevant.

Man, look at that Klinked-out distributor insulator disc !!!

Super good call, but a little additional explanation is in order:

Indeed, he is showing the set up that lives in the M104 and M120 engines with distributor ignition systems. Those love to cause single cylinder misfires on acceleration, and they are usually found because the rotor "nests" inside those with only a few millimeters between the rotor electrode and the cylinder head, hence they are readily recognized as the serious electrical insulators that they are.

While he mentions the same part in relation to the M119, and it's great that he does, that scenario is a little different. There is much more space between the rotors and the cylinder head on the 119 installation. The problem with the M119 is NOT arcing through the plates as occurrs with the M104 and M120. In fact, one can take the plates out of a M119 and grind all of the material away leaving only the thinnest section of ring to hold the o ring and space the cap. In other words, just make a sealing washer out of it. The M119 thus fitted will run FINE under almost any conditon of ignition load. Try that with a M104 or M120, and just the ignition voltage requirement of sudden hard acceleration from idle will usually stall the engine as the spark arcs to the head...

So, that plate, absolutely vital on the 104/120 is only kind of an electircal / dimensional / drippy oil seal oil goes behind it, etc. "insurance policy" on the M119, and ironically the usual problem they cause is emitting the fog, attracting moisture, thereby promoting arcing and crossfiring THROUGHOUT the distributor.

So what I'm saying is deal with the plates to stop chronic distributoritis. HE is saying replace the plates to fix your misfiring. It's related but different. Note that with the M119 one can replace the caps and rotors and they are usually OK for a while. You can replalce the caps and rotors all you want on the M104 and M120 and if the plate is an issue, they keep right on misfiring. There is usually no temporary "hey it's fixed!" joy as they trick you into with the M119...

 

[samiam44]

Re: 1995 E420 coughs stutters & backfires

My vote is moisture in the caps.


Make sure the o-ring seals are there to seal the caps. My passenger side seems more prone to this than drivers side.


M

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

So what I'm saying is deal with the plates to stop chronic distributoritis. HE is saying replace the plates to fix your misfiring. It's related but different. Note that with the M119 one can replace the caps and rotors and they are usually OK for a while. You can replalce the caps and rotors all you want on the M104 and M120 and if the plate is an issue, they keep right on misfiring. There is usually no temporary "hey it's fixed!" joy as they trick you into with the M119...

I agree 100% with Klink. One of my 500E's arrived after purchase with broken insulator plates. Car ran GREAT. No misfiring. As Klink said, the issue is with the fluid on the plates (and/or caps/rotors).

I have a fresh set of "problem insulators" that I will be getting photos of soon. Of interest in this case, the inside of the insulators is bone dry. Not even a hint of fluid. The back side of both has a coating of fluid present... not dried residue, some sort of moisture. I believe it is NOT water, as it never evaporates. I'm with Klink that somehow this fluid, whatever it is, may be emitted by deteriorating insulators. However I can't say for sure. I figured all this out AFTER the problem car (E420, btw) received new caps/rotors/insulators to fix the problem. The previous caps/rotors were only 2 years / 15kmi old and in hindsight, I think they were fine... and it was the moisture on the insulators causing the issue. There was zero engine oil leakage in this case, btw... some cars will dribble engine oil at the lower edge of the insulators, from leaky cam solenoids, or from the cam sprocket seal in severe cases. My insulators just had weird fluid coating on the rear.

Further complicating the issue: My E420 would only misfire after this exact scenario: Car must sit for at least 1 week, then start and drive for ~10 miles, shut engine off for 5-10 minutes, try to restart, result is severe misfire and/or a no-start condition. Wait 30 minutes, car starts immediately and runs flawlessly, and continues to run perfectly... until it is parked for at least 1 week, then the scenario above reoccurs.

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

Side note: I'm not sure replacing the O-rings has much effect... I've not seen them deteriorate. I'm also not sure that moisture (water, not other fluid) is the root cause of the issue. Maybe over time we'll be able to collect enough data points to figure out what's going on inside these buggers.

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Yep, Gixxer. I'm saying that it is either emitted by the plates, and/or that emission from the plates attracts moisture just like brake fluid, hence it doesn't dry because it is always attracting more water. I lean towards the hydrophillia theory as the moisture is almost never seen in desert-like places, just the strange fogging. In humid climates, the foggy objects usually also have fluid on them. I don't think it has ever been as simple as "water gets in there". For that matter, how could it. It's not like these are subjected to splash water if everything is in place...

 

[sheward]

Re: 1995 E420 coughs stutters & backfires

Further complicating the issue: My E420 would only misfire after this exact scenario: Car must sit for at least 1 week, then start and drive for ~10 miles, shut engine off for 5-10 minutes, try to restart, result is severe misfire and/or a no-start condition. Wait 30 minutes, car starts immediately and runs flawlessly, and continues to run perfectly... until it is parked for at least 1 week, then the scenario above reoccurs.

I had the exact same symptom on my previous 93 car. I never got around to addressing it as I wasn't driving it much, however I was confident that it was due to the caps/insulators. It began soon after I washed the engine.

drew

 

[bing]

Re: 1995 E420 coughs stutters & backfires

Chronic cap-itis/distributoritis can lead to Klinkitis if not diagnosed early!

Man, so many M119 owners in the UK suffer from this due to our damp climate and I've advised so many to look at the condition of these plates and to replaced them if no record being done so . Trouble is a lot of owners are in denial coz they're so damn expensive for what they are. False economy if you ask me .. Doh !

 

[gerryvz]

1995 E420 coughs stutters & backfires

OMG Klink-itis! Heck of a naff condition for sure.


klink·i·tis
/kliNGk īdəs/
noun - automotive

A functional disorder peculiar to 1990s-era Mercedes-Benz engines where a severe misfire and/or non-starting condition occurs due to the penetration of severe levels of moisture and/or humidity into the high-voltage ignition components used for transmitting electricity to the engine's spark plugs.

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

For the record: I've never had issues related to pressure washing M119 engines, and the mystery fluid/misfire issue has not seemed to be related to humidity levels (Boise is damp in winter, but near-Arizona arid in summer). However, I don't spray near the distributors, I only pressure wash below that level to remove grime from oil/PS/SLS leakage. Be careful if you are spraying water anywhere on an M119, and if your problems appear afterwards, it's pretty likely not to be coincidence.

What would be interesting is for someone who finds the "dampness" on the insulators, to wipe everything dry as Klink described in post #6, then check them periodically to see if the mystery fluid returns... and if there is any correlation to humidity levels the car has experienced. (Assuming it's not related to pressure washing, or otherwise artificially introducing water near the caps).

Some more data points: I've seen numerous insulator plates with the measles, as shown in Jon's post #8 above. However it has usually been a dry measles, and the engine ran fine with insulators that looked that way. Additionally, my wife's 92 500E has the original (black color) insulators dated 1991 and they look absolutely brand new front & back, no evidence of residue. Very weird.

 

[maplevalleyhammer]

Re: 1995 E420 coughs stutters & backfires

Thanks For the diagnostic idea guy's. I will address and report back as soon as I can get to it!

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

I had the exact same symptom on my previous 93 car. I never got around to addressing it as I wasn't driving it much, however I was confident that it was due to the caps/insulators. It began soon after I washed the engine.

drew

For the record: I've never had issues related to pressure washing M119 engines, and the mystery fluid/misfire issue has not seemed to be related to humidity levels (Boise is damp in winter, but near-Arizona arid in summer). However, I don't spray near the distributors, I only pressure wash below that level to remove grime from oil/PS/SLS leakage. Be careful if you are spraying water anywhere on an M119, and if your problems appear afterwards, it's pretty likely not to be coincidence.

What would be interesting is for someone who finds the "dampness" on the insulators, to wipe everything dry as Klink described in post #6, then check them periodically to see if the mystery fluid returns... and if there is any correlation to humidity levels the car has experienced. (Assuming it's not related to pressure washing, or otherwise artificially introducing water near the caps).

Some more data points: I've seen numerous insulator plates with the measles, as shown in Jon's post #8 above. However it has usually been a dry measles, and the engine ran fine with insulators that looked that way. Additionally, my wife's 92 500E has the original (black color) insulators dated 1991 and they look absolutely brand new front & back, no evidence of residue. Very weird.

I have seen it just after an engine wash done by expert hands on more than one ocasion. That has also made me think of a moisture ATTRACTION situation. I imagined that the extra humid enviornment just after / during an engine wash was a "last straw" situation, finally creating the unfavorable conditions supporting misfiring.

 

[maplevalleyhammer]

Re: 1995 E420 coughs stutters & backfires

I am having trouble sourcing the insulator discs, any recommendations?

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

http://www.amazon.com/dp/B006K949YS/

http://www.autohausaz.com/search/product.aspx?sid=foyp543lpuybjtfgheuv2g55&partnumber=1230500240

 

[jgt157]

Re: 1995 E420 coughs stutters & backfires

Hmmmm, I'm experiencing this symptom as well. Guess I'll be replacing these as well.

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

Hmmmm, I'm experiencing this symptom as well. Guess I'll be replacing these as well.

Try removing yours first, and if there is any fluid residue on the back side, clean & replace... see if that helps or cures the problem. It's free and worth a try before shelling out $150-$200 for a pair of new plastic teacups.

 

[maplevalleyhammer]

Re: 1995 E420 coughs stutters & backfires

Dave, Is the Amazon part the same as the Auto House AZ?
Looks like the Amazon part may just be the rotor.
Thanks as always for your help!!!

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

Dave, Is the Amazon part the same as the Auto House AZ?
Looks like the Amazon part may just be the rotor.
Thanks as always for your help!!!

Ignore the Amazon description - the Bosch part number 1230500240 is correct.

 

[maplevalleyhammer]

Re: 1995 E420 coughs stutters & backfires

Amazon had only 1 so I had to pay a little more @ Auto House.
Thanks for the tip!!!

 

[bing]

Re: 1995 E420 coughs stutters & backfires

Expensive buggers but you shouldn't have to change 'em for a long long while. Most owners replacing these are probably on the original ones from day 1 , so worth doing at least once IMO .

 

[gerryvz]

Re: 1995 E420 coughs stutters & backfires

OMG Klink-itis! Heck of a naff condition for sure.


klink·i·tis
/kliNGk īdəs/
noun - automotive

A functional disorder peculiar to 1990s-era Mercedes-Benz engines where a severe misfire and/or non-starting condition occurs due to the penetration of severe levels of moisture and/or humidity into the high-voltage ignition components used for transmitting electricity to the engine's spark plugs.

 

[samiam44]

Re: 1995 E420 coughs stutters & backfires

were these insuators originally made by Beru. I noticed the most 91-94 seem to be black originally??



Michael

 

[garrison]

Re: 1995 E420 coughs stutters & backfires

FWIW ... driving the car regularly will eliminate the problem ... caveat, worn parts "might" contribute ... my '92 400E @ 243k will exhibit symptoms you're describing especially if I let it sit for a week or more and combine the sitting around with short trips ... the cure? ... drive the thing to heat it up real nice ... these beasts are meant to be driven ... let the engine come up to operating temp and get it nice and warm on a leisurely trip down your local boulevard ... make sure your temp gauge has been reading the 80C or so for a bit ... that means the oil has begun to warm up ... take your time doing this ... and don't stop and putz around with a couple of short stops ... and then take a couple two or three runs up to red line or thereabouts in second gear ... freeway on ramps are good for that ... that will keep it running just swell ... by the way, I've replaced my rotors and caps a couple of times since purchase about ten years ago at 91k ...

Hope these tips help.

garrision
'92 400E @ 243k
'95 E320 @ 183k

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

FWIW ... driving the car regularly will eliminate the problem ... caveat, worn parts "might" contribute ... my '92 400E @ 243k will exhibit symptoms you're describing especially if I let it sit for a week or more and combine the sitting around with short trips ... the cure?

So, have you ever removed the insulator plates shown above, checked them for any sign of fluid or degradation, and either cleaned or replaced them?

My 500E's sit in storage for 4 months during the winter and come out of hibernation running flawlessly. Something is wrong with your 400E if it won't do the same. See post 17, 23, and 29 above.

 

[garrison]

Re: 1995 E420 coughs stutters & backfires

Dave M,

To your point, when these ignition parts are in good order, indeed one can store a car for the several months you mentioned and the beast should fire right up ... in fact, about six years ago, I hit a deer with the 400E -- light hit off the passenger side front ... I had the car in my garage for about four months without starting ... I replaced the a/c system (evaporator, compressor, etc ... and the damaged radiator, a/c condenser, aux fan brackets, right side Euro light, etc ... when all was done, including flat-bedding to my local Benz body shop experts for a new hood ... and I was ready to charge the a/c system, the rascal fired right up on the first crank ... I think my observation is simply when these ignition parts get some age and miles on them, it's time to replace.

regards,

garrison k
'92 400E @ 243k
'95 E320 @ 183k

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

That looks like the "heartbreak of psoriasis" As Root Boy Slim (RIP) used to sing "so much flaky skin in my Cadillac, can't even see to drive"...
[youtube]ziAxvvJsgic[/youtube]

 

[maplevalleyhammer]

Re: 1995 E420 coughs stutters & backfires

Update!
Turns out that my problem was actually a CPS, Crank Position Sensor!

 

[Ascension]

Re: 1995 E420 coughs stutters & backfires

http://www.amazon.com/dp/B006K949YS/

http://www.autohausaz.com/search/product.aspx?sid=foyp543lpuybjtfgheuv2g55&partnumber=1230500240

FCP has the Bosh insulators in stock and as is pretty normally at around $20 or so less than Autohaus + FREE SHIPPING
https://www.fcpeuro.com/products/mercedes-distributor-dust-shield-1191580188

 

[Maui]

Re: 1995 E420 coughs stutters & backfires

How can that silly thing be $75? That's robbery.

 

[Ascension]

Re: 1995 E420 coughs stutters & backfires

How can that silly thing be $75? That's robbery.

Agreed and it's the same with cap rotor and wire cost on these engines. However buying from FCP at $75 with free shipping is not as much of a robbery as the $93 + shipping from Autohaus is .

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

How can that silly thing be $75? That's robbery.

If they did not make it out of some horribly expensive buttafuoco, it wouldn't be able to disintegrate into the wet, electrically conductive mess that it does. I'm sure it took decades of research, and billions of D-Marks to come up with such an incredibly feeble material...

 

[gsxr]

Re: 1995 E420 coughs stutters & backfires

... such an incredibly feeble material...

Klink, is IFM a variation of the factory-sanctioned FPP?

 

[Klink]

Re: 1995 E420 coughs stutters & backfires

Klink, is IFM a variation of the factory-sanctioned FPP?

If not, it sure as hell should be. Then again, maybe not.
The FPPs worked pretty well. Those M119 ignition distributor plates, not so much...

 

[brock]

Misfire Stumble - Won't Rev

I started my 1992 500E for the first time in a couple months last night and had a strange phenomenon happen.

It started and idled fine but when I went to rev it up a bit I got a stumbling/misfiring/rough running/coughing reaction from the engine. I tried goosing the throttle to rev it up and and it tried to rev but the stumble was preventing it from revving freely. I did not drive it for fear of becoming stranded.

I have a Transmission Overload Protection Switch not Closing code, for which I have a replacement switch and o-ring kit that needs to be installed, not sure if this would have an effect on this issue.

Where should I look next?

Any and all info would be much appreciated.

Thanks

 

[JC220]

Re: Misfire Stumble - Won't Rev

It could be moisture has crept into the distributed cap(s)

Best thing to do is remove both caps / rotors and insulating plastic disc behind to make sure everything is 100% dry.

 

[r44raven]

Re: Misfire Stumble - Won't Rev

My thoughts are the same as JC220. There are many members here much more knowledgeable than me on this matter, and hopefully they will chip in, but certainly damp behind the caps/rotors would be my first port of call.

 

[gsxr]

Re: Misfire Stumble - Won't Rev

Trans O/L switch has nothing to do with this problem. The O/L switch, if defective, can cause weird full-throttle upshift behavior but that's about it.

The misfire is most likely related to caps/rotors, particularly the insulator behind the rotor bracket - search the forum for details. This will not trigger any codes on any modules, btw. I'm assuming you have checked the spark plugs and they are recent/clean non-resistor F8DC4 (or equivalent from NGK/etc); and the upper wiring harness is not original. The fact that the problem occurred after being parked for 2 months makes me strongly suspect the fluid-on-the-insulator issue discussed elsewhere. I had the identical issue on one of my cars and it would only act up after being parked for 2+ weeks... drive it daily and it was fine.