Misfire/rough after sitting

[BobC]

Gentlemen,

A friend's 1993 500E, with high mileage, has this problem: After sitting for a week or more, the car starts fine, runs well for about a minute, then starts to misfire and run rough. After a freeway drive, it returns to good running operation. The mechanic checked fuel and injectors. Any suggestions, especially for high mileage vehicles? Thank you.

Bob

 

[gsxr]

How old are the distributor caps/rotors and spark plugs, and what brand/model plugs are installed? I'd start by pulling the caps and plugs for a quick inspection.

 

[zman]

Bob, this is very normal. I store mine for the winter, and after every first start, it starts to sputter and eventually die. Upon experiencing this the first time, I removed the caps and sure enough carbon build up inside. At that time I just carefully cleaned them up using a dremel with a small wire wheel and it ran fine after that. Dave is 100%.

 

[dbb7697]

i experience the same issue. New plugs and caps and rotors and the issue is still there.
Gas mileage improved greatly with the changes.
Could it be wires? Maybe carbon buildup on valves. My car only has 55, xxx miles.

 

[wgnguy]

I have the same issue, changed the wiring harness, fuel pressure has been tested, caps and rotors where changed. I'm hoping someone has a solution, this is taking away the enjoyment of driving the car.

 

[gsxr]

I have the same issue, changed the wiring harness, fuel pressure has been tested, caps and rotors where changed. I'm hoping someone has a solution, this is taking away the enjoyment of driving the car.

First, welcome to the forum!

1) What brand / type spark plugs are installed? These older ignition systems do not like resistor plugs, or fancy plugs with platinum/yttrium/etc electrodes. Bosch F8DC4 (or Beru/NGK equivalents) is what should be used.

2) Have you replaced the insulators behind the distributor caps? This is often overlooked, as noted in this Star article:
http://www.w124performance.com/docs/mb/ ... g_STAR.pdf

3) How old are the plug wires?

 

[bendover]

This helps me alot! I have the exact same problem on my ride! Is it a big project to change the insulators behind the rotor?

Just to verify your theory. Nr 14 (PN: 1191 580 188) is the insulator that need to be changed?

Is the bolt (incl. the bracket) the only thing I have to remove for the insulation to come off? (rotorcaps, rotors are already removed :roll: )

Regards // Johan

Edit: just placed an order at my workshop. "Only" $165 each... $330 in totalt...! Hope it helps

 

[gsxr]

To replace insulator #14, you only need to remove the rotor bracket #5, which is held in place by a single bolt #8. That's it - very simple. When re-installing, I would recommend using a very small amount of BLUE Loc-Tite on the threads of bolt #8, and also on the threads of the three small bolts which fasten the rotor to the bracket.


On a side note, I experienced a variation of this issue on my one E420. It happened after the car sat for several weeks. It started and ran fine for about 10-15 minutes of driving at 30-60mph. Then when stopped at a traffic light, it would misfire badly, and when trying to accelerate, it would barely move the car at all. Once gradually coaxed up to speed (sputtering the whole time), it would smooth out at light load while cruising at ~55mph, and it would also run ok at WOT to redline, but accelerating off idle it was terrible. It did this several times after the car was parked for days or weeks. The bizarre part? After driving it several days in a row, the problem disappeared completely. So, I was never able to diagnose it. The main difference compared to the original issue in this thread is that my car did not act up until shortly after it reached full operating temp. It was fine when cold.


UPDATE: The issue described above was later pinpointed as defective insulators behind the distributor caps. Replacing the insulators cured the problem permanently. This has been discussed at great length in more recent threads on this forum. Click here for one of the epic threads.

 

[bendover]

To replace insulator #14, you only need to remove the rotor bracket #5, which is held in place by a single bolt #8. That's it - very simple. When re-installing, I would recommend using a very small amount of BLUE Loc-Tite on the threads of bolt #8, and also on the threads of the three small bolts which fasten the rotor to the bracket.


On a side note, I experienced a variation of this issue on my one E420. It happened after the car sat for several weeks. It started and ran fine for about 10-15 minutes of driving at 30-60mph. Then when stopped at a traffic light, it would misfire badly, and when trying to accelerate, it would barely move the car at all. Once gradually coaxed up to speed (sputtering the whole time), it would smooth out at light load while cruising at ~55mph, and it would also run ok at WOT to redline, but accelerating off idle it was terrible. It did this several times after the car was parked for days or weeks. The bizarre part? After driving it several days in a row, the problem disappeared completely. So, I was never able to diagnose it. The main difference compared to the original issue in this thread is that my car did not act up until shortly after it reached full operating temp. It was fine when cold.

Thank you for your help Gsxr! I hope these two parts will make a change for me and my 500E! And no, I wont forget the blue Loc-Tite
Btw, the symptom you describe that you had on your E420 is exactly the same as my symptoms on my car. Hmmm....
If I drive it on a daily basis I dont have any problem....

 

[bing]

just placed an order at my workshop. "Only" $165 each... $330 in totalt...! Hope it helps

Johan, I thought parts in the UK are expensive but at $165each , Sweden tops it!
Paid £77 each here in the uk, AutohausAZ in the US on sale for $78each!..make you ill doesn't it?!
Can't quite understand just for a bit of uncomplicated design hard plastic cost so bloody much

Anyway, am glad it solved your issue and you can now sleep tight

 

[bendover]

Johan, I thought parts in the UK are expensive but at $165each , Sweden tops it!
Paid £77 each here in the uk, AutohausAZ in the US on sale for $78each!..make you ill doesn't it?!
Can't quite understand just for a bit of uncomplicated design hard plastic cost so bloody much

Anyway, am glad it solved your issue and you can now sleep tight

I dont know if it helps yet. But I sure hope the two plastic ($$$gold$$$!) will solve the issue.

And yes, it makes me a little bit ill hahahaha
But if I buy them at my local work shop I will have a better warranty IF something should happen in the future 2 years (OOOOVERKILL).

 

[mocarnut]

I'm experiencing the same symptomatic behavior with my 500E that gsxr had with the E420 above. Without throwing
an entire series of $300 -$400 parts at the intermitant problem, I'm searching the forum and tracking down the bad order part(s). A member suggested replacing the sealing ring between the air filter housing and the MAF. Seemed to help until the engine warmed up. Caps and rotors next. Then checking wires and plugs... Looking for authentic Bosch parts outside dealerships in STL.

 

[bing]

I dont know if it helps yet. But I sure hope the two plastic ($$$gold$$$!) will solve the issue.

Oh sorry, thought it has, based on your original thread. Yes, lets hope that these made of "gold plastic" cures it!

 

[bing]

I'm experiencing the same symptomatic behavior with my 500E that gsxr had with the E420 above. Without throwing
an entire series of $300 -$400 parts at the intermitant problem, I'm searching the forum and tracking down the bad order part(s). A member suggested replacing the sealing ring between the air filter housing and the MAF. Seemed to help until the engine warmed up. Caps and rotors next. Then checking wires and plugs... Looking for authentic Bosch parts outside dealerships in STL.

Try these guys :

On Sale right now

http://www.autohausaz.com/search/produc ... utor%20Cap

Recently ordered all my ignition parts from them and shipped all the way here in the UK. Even with taxes paid locally I still made quite a bit of saving.

And yes, very annoying and spendy sometimes when it comes to misfire issues as most go through a process of elimination. Understandable of course as we try to save costs.

 

[dbb7697]

I would love to here the success of the replacement of the insulator discs. The part number you reference is that the correct part number?
Thanks

 

[bing]

The part number you reference is that the correct part number?
Thanks

see the link below, this is the insulator/cover that's overlooked quite often, and they should come with the rubber seal also.

http://www.autohausaz.com/search/produc ... ap%20Cover

 

[bendover]

Yes, it is the correct pn: 119 158 0188 on the insultators.

They are now changed in to new OEM parts. Did help? NO, it did not help me at all.
I hate cars.....even these ones....I dont care if they are sent from heaven hahahaha *ironi*

Next step, measure the resistance in the ignition cables when they are hot.
(I dont have any problem with a cold engine. I have only measured the ignition cables when they where cold).

It will continue......

Thank you so much for your help so far!

 

[gsxr]

Aaaaaargh. Jono has a theory that it could be related to moisture in the caps. Any chance the problem only occurs after sitting for a while in high humidity, or after a healthy rain storm?

The symptoms on my E420's have vanished for the moment so I've been unable to diagnose further.

 

[bendover]

No, it doesent matter if it has rained or if the sun have been shining the last century hehe.

When I changed the insulators behind the rotors yesterday I could not find any moist. I dryed everything very careful and continued the assemble.
When it was time to start her up she ran almost perfect. After a while, much earlier than before she starts to misfire as hell....
As said before. I will measure the ignitionwires again but on a warm engine. Wish me luck

I will not stop the pursuit of excellense until I find some answers. It cant be impossible!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[bendover]

Small update:

I have measured the resistance in the ignitionwires (I have also cleaned them from a little corrision). Nothing awkard on them....
We removed the spark plugs to see if they were wet (because of the misfiring, sounds like the engine gets way to much fuel). But no, they are in very good shape!
Wich leads me to think that the engine get less fuel than she needs...

I have also checked the sender units for the cooling water. No errors on those (I simply them when the engine starts to misfire to see if the enginge would run better when it thought it was cold). But no change at all....

The O2 was next. It should send 0,1V to 1,0V if I´m correct? Mine only reaches up to 0,1V to 0,7V. Is this THE problem?

Thanks in advance // Johan

 

[DerFuror]

Wich leads me to think that the engine get less fuel than she needs...

When was the fuel filter last replaced?

Fuel delivery can exhibit various behaviors based on the amount of sediment in the filter under pressure. High amounts of sediment can cause difficulty immediately on startup. Smaller amounts of sediment when placed under pressure can eventually combine together to restrict fuel delivery & cause difficulties while out on the roadway.

You may wish to consider:
- Fuel Filter condition
- Fuel Pressure Test/Fuel Pump performance
- Fuel Pump electrical connection condition

 

[bendover]

I replaced the fuelfilter this spring. I will, as soon as it arrives, replace the O2-sensor first. If that does´nt do the trick I will continue with the issues you suggest.

Thank you so much for your help and for taking the time to help me solve this problem.

// Johan

 

[gsxr]

Johan, the O2 voltage will vary from roughly 0.1 to 0.9 (max of 0.0 to 1.0) but I doubt that a reading of 0.7 is a problem. However, if the O2 sensor is fairly old, it should be replaced anyway - the rated life span is approx 60kmi / 100kkm.

FWIW, my silver E420 has a new O2 sensor and still did the weird misfire thing after sitting for ~10 days, parked in the garage... also new plugs, new fuel filter, caps/rotors were fine, etc. Hasn't hiccuped since but it's been driven more often as well.

If you have a digital scanner - just curious, what are the LH adaptation values for lower, upper, and idle?

 

[bendover]

The O2 sensor is now changed (thank you T.Luhr at www.overboostracing.se)
We think it´s the original one we replaced. But the most important thing, did it work after this?
No.... it´s something else causing the misfire... (I even changed the MAF (had one in stock just in case, did not help).

Gsxr: No, I dont have a digital scanner. Sorry!

 

[Christian_K]

Did you reset the self-adaption values after the O2-Sensor and MAF change? This is a strong must! Otherwise it will take a few 100 miles until you notice *any* change.

 

[Cadence]

Did you reset the self-adaption values after the O2-Sensor and MAF change? This is a strong must! Otherwise it will take a few 100 miles until you notice *any* change.

Is this as simple as disconnecting the battery for 30 seconds or is a tool required?

 

[gsxr]

Is this as simple as disconnecting the battery for 30 seconds or is a tool required?

Depends on the year of the LH module. The later ones (93-up) will reset if you disconnect the battery for 5-10 minutes (not sure if only 30 seconds will work). The 92 modules must be reset with a digital scanner, or with a hand-held LED blinker box. Then it takes a few days / few hundred miles of driving for the adaptation to adjust again.

 

[bendover]

I tried to disconnect the battery for approximately 15 min.
No change... It runs on ~4 cylinders :-o .

I will try to replace the ignition coils. That could be it.

To be continued....

 

[bendover]

Well, there is a 400E in a local scrapyard here in Arvika. I borrowed one of the ignitioncoils from that car and mounted it on my car.
No improvment....

Problem/symptom:
If I disconnect the ignitioncoil (the one closest to the fender, drivingside), while the other one is still mounted, the engine wont fire up at all (not even on four cylinders)).
If I disconnect the igntioncoil (the one closest to the engine), while the other one is still mounted the engine fires up on four cylinders.

So, the distributor cap (the one on the passenger side) does not work properly. I do not know if it is an ignition problem or fuel problem yet though...

Troubleshooting:
- I have tried to swap the cable between the ignitioncoil and the distributorcap - No change.
- I have tried to swap the ignitioncoil - No change as said before.
- I have tried to swap the EZL ignition control unit (from a 400E) - No change.

I´m open for ideas. Can it be a fuelpreassure related problem?

Thanks in advance!

Ps. I have already tried a fuelsystem cleaning product from Red line (or was it Omega).

 

[gerryvz]

Sounds more and more like an EZL problem to me. When my EZL died, it killed one-half of the motor so it was only running on one bank of cylinders. If you connect the car to a scope you will be able to tell what is happening with the car electrically, per cylinder, in about 5 seconds while the car is running. That way you can tell if it is indeed an ignition or fuel related problem. An hour with a good mechanic with the right equipment will tell you quite a lot.

Cheers,
Gerry

 

[bendover]

Read my edit gerryvz. I used the wrong english word for EZL (I think)...
And yes, the car must be submitted to a good mechanic. But my local MB-workshop did not have time for a while (3-4 weeks).

 

[gerryvz]

Ahh, OK got it. Thanks for clarifying on that. Again any shop with a scope ought to be able to connect it in 1 minute and running the car should be able to tell electrically what is happening with the motor. That would diagnose or eliminate any spark/ignition related problems. It really does seem (to me) to be a problem of a more electrical nature, not a fuel related problem.

A 400E EZL may not work in good harmony with a 500E though. It's one of those parts that is specific to the model (though any 5-liter engine EZL should at least drive the 500E motor fine, perhaps just not optimally).

Cheers,
Gerry

 

[gsxr]

What was the part number of the 400E EZL and the 500E EZL...? Not all are interchangeable. It would be better to test with a known-good 5.0L EZL if possible.

 

[bendover]

400E - Part number: 014 545 45 32
500E - Part number: 014 545 43 32

I know there are one specifik EZL/model. Talked to mr Arnt aka "500AMM" a week ago (he visited me) and we discussed, among other things, how important it is to get the correct EZL.
But I thought the EZL from the 400E would help me out in my troubleshooting process. And yes, I should get one EZL from a 500E to test with if it is possible.

Thank you so much for your help!

 

[gsxr]

I think that for test purposes, the 014- 400E EZL may suffice... but I can't say for sure. I'd see if you can get a 5.0L EZL (any part number, but must be 5.0L!) to test with. If you want/need to buy a good used EZL, drop me a line... I may have a spare that I'd sell, in case you can't find one locally.

 

[bendover]

Mr Gsxr, you´ve got a PM

 

[bendover]

Thank you for a quick reply mr Gsxr.

Update:
I have continued my troubleshooting and I found an interesting and a possible cause of failure...
One of my (passenger side) catalytic converters is toasted and probably plugged (it rattles inside on lower rpm and especially when you hit it with something hard).
My friend Tommy Luhr at www.overboostracing.se will replace the two original catalytic converters into one 3" race catalytic converter.
I hope this is the error cause.... To be continued!

Ps. I have sparks on every plug, Tommy had an amazing little "pen" with a "diode" in it that he just held to the wire. It started to flash on every wire.
We did even spray the ignition wires (on the spark-plug side and on the distributor cap) with a small amount of water. No arcing what so ever

 

[bendover]

So, this is what it looks like under my fivehundred right now. Did it help? Does the engine run without any problems?
No, not right now. It may have damaged my sparkplugs so I will have to replace them with new ones before I can tell if it helped.

The catalytic converters were in a really bad shape so I had to change them anyway. So, nothing unneccesary is done
The new catalytic converter is a racewowow. It will last up to 6L engine with 650hp.

To be continued (again).....

 

[bendover]

I now know that the fuel pressure is ok (~4 bar = ~58 psi). Even when it misfires...
Any new ideas anyone or is it still the EZL that pops up in your minds when reading about my symptoms and troubleshooting??

 

[gerryvz]

Fuel pressure should be around 50-55 PSI at idle, and should go up to 60+ when the engine is revved. If that is happening, then fuel delivery is OK (at least as far as the fuel rail).

Still sounds to me like an EZL/ignition electrical problem.

Cheers,
Gerry

 

[bendover]

I thought so! Thanks again! If you read my post #39 again you will find out that I converted the bar into psi

 

[hillsdonsmith]

Gentlemen,

A friend's 1993 500E, with high mileage, has this problem: After sitting for a week or more, the car starts fine, runs well for about a minute, then starts to misfire and run rough. After a freeway drive, it returns to good running operation. The mechanic checked fuel and injectors. Any suggestions, especially for high mileage vehicles? Thank you.

Bob

We have a'93 500E also with the same problem. Runs rough if car has not been started for a week, but also now has episodes every 4-6 weeks, where it does this within a few minutes of startup, sometimes as long as 5 minutes into a drive. It's gonna be a bitch if it happens when we are turning left into traffic some day...

From the replies here, this is obviously a common problem with the car. I dropped it off at local Benz dealer last week with the hope of some diagnostic love - all they did was take it for a test drive. Won't be going there again...

Does anyone know of a good mechanic familiar with these cars on west coast of Canada? There has to be someone who knows exactly what this is, instead of all this guess-work.

 

[gsxr]

Does anyone know of a good mechanic familiar with these cars on west coast of Canada?

T500 or valvfloat are in S/W Canada, they may have a recommendation.

There has to be someone who knows exactly what this is, instead of all this guess-work.

This someone is hiding very well at the moment. To date, the mystery remains unsolved, although a lot of information has been posted ruling out what the problem isn't.

 

[bendover]

Update:

I talked to a friend of mine who owns a 500E. He lend his EZL to me. I tried his EZL. No change.
And yes, this someone (if he/her exists) is really hiding well. And our troubleshooting must be one of a kind. I now know what´s not causing the problem. INTERESTING!

hillsdonsmith, I can assure you. 500Eboard.com/forums is tha shit! Allot of helpfull, intelligent and interested members with good experience. So, this is the best place I think.

To be continued....

 

[bendover]

I now know whats causing my problem with misfiring! And it spells G A S K E T!
- Intake manifold gasket.
- Diffusor seal (Is that the correct english word?)

It took MB here in Arvika estimated 30 min to find the error causing the misfire.
They simply sprayed it with ether (starting gas)!

Its not always the big, expensive stuff *lucky me*
I will replace those "bastards" next friday!

 

[gerryvz]

Nice work. Indeed I find much more often than not that it's simple causes for seemingly complex problems. It just takes time, effort and thinking to come up with the solution.

Keep us informed and take photos of the process. I've not yet seen intake manifold gaskets be a problem on the M119 so this is a bit of a "new leaf"

Cheers
Gerry

 

[Taxi Driver]

I now know whats causing my problem with misfiring! And it spells G A S K E T!
- Intake gasket.
- Diffusor seal (Is that the correct english word?)
It took MB here in Arvika estimated 30 min to find the error causing the misfire.
They simply sprayed it with startgas! Its not always the big, expensive stuff *lucky me*
I will replace those "bastards" next friday!

What do you know? Who would have guessed, this tell us to begin in the ( shallow end, not in the deep end)
The cost of a can of ether (starting spray) must be the cheapest of diagnose tools. Hope it will run smoth as honey. Roger

 

[bendover]

I will keep you guys informed! And I will take alot of photos from the process, trust me!
I hope that this procedure will solve all my problems with misfire and that my effort and hard work will pay off in the end!
I´m looking for a smoth idle and no misfire what so ever regardless how long the car hasnt been in use

I hope this thread will help all you guys with a W124.036 with a rough idle (small, small misfire at 7-800 rpm) or a rough misfire after sitting.
Is it even possible that you mr Gsxr have this problem with your car that you´re refering to earlier in this thread?

Best regards // Johan

 

[bendover]

So, this is the spare parts that I will replace this Friday (2 September).

 

[bendover]

Not only do I have the spare parts I also have a workinstruction so, what can go wrong