Engine still skipping a beat every few seconds

[gsxr]

I'd expect the switch to cause issues at idle, not when driving. If it's misfiring under load when driving... my money is on the MAF.

The greenish/yellowish residue on the rear distributor insulators seems somewhat normal, at least I've seen it on many cars, and it usually doesn't cause problems. Now if your insulators are failing such that the spark is going through and grounding on the metal on the other side, that's bad.

 

[ivanned]

If the MAF was the culprit wouldn't the issue go away if I drive with the MAF disconnected?

I did that and symptoms remained. And they are definitely temperature related.

As far as the insulators I did not see anything obvious: no darkening or black stripe or dot marks. The o rings were nice and soft.

 

[emerydc8]

If it's temperature related, have you considered whether it could be carbon buildup on the top of a piston that is causing an occasional pre-ignition. Maybe run a few bottles of Chevron Techron through. It's cheap to try it.

 

[Jim]

Are these carbon spots that small or are they visible with a naked eye?

Think slightly curved line 3 or 4 mm long located at the same radius as the plug lead pillars. Visible if "soot" trapped.

 

[ivanned]

Thanks guys. All of this is appreciated. I will reinspect the shields for sure but first time did not see anything.

 

[ivanned]

Just had a thought, what are the consequences of the throttle linkages to the ETA not adjusted properly and the learning procedure not performed?

The last time the ETA was removed was to replace the ETA to the intake gasket. The shop that did it may or may not have known to do either procedures so I am wondering what would happen if this is all messed up?

 

[gsxr]

I've heard rumors of a so-called ETA learning procedure, but I've never found factory docs confirming this, and I've never had to do it on any of my cars after a different ETA was installed.

 

[ivanned]

I see.

Last time I was at ENI motorsports they were working on a 1970s Ferrari and they had brought in a guy with a whole minivan full of equipment to diagnose and hopefully correct drivability issues with it. I asked him for his info and he said he works for shops only.
My question is: Are there any diagnosticians out there whose business is to go through everything and figure out what is wrong with a car. I am willing to spend some cash for someone to show me what is out of spec.

Has anyone heard of such service or know a diagnostic genious? I feel a lot of enthusiasts can benefit from such thing.

 

[500AMM]

Hello Ivan.

Based on intermittent misfiring, lost midrange power, over to almost stagger, I guess you have condense build up in the fuel tank. The carborn filter should help on this, but if you have a water puddle splashing around in the bottom of the fuel tank, the fuel filter will be saturated even if it is new, and some water will slurp through the system at some point.

Drain the fuel tank, top up, and add a bottle of "condense remover" or what it is called over there.
As for a bad new cap/rotor - I recall two years ago, Owner Bendover got a malfunctioning brand new OE ignition coil from the MB stealer, so that can happen.

Cheers

 

[gsxr]

My question is: Are there any diagnosticians out there whose business is to go through everything and figure out what is wrong with a car. I am willing to spend some cash for someone to show me what is out of spec.

Has anyone heard of such service or know a diagnostic genious? I feel a lot of enthusiasts can benefit from such thing.

I'd be willing to give it a shot but I think the drive to Idaho might be a little long...

 

[Glen]

My question is: Are there any diagnosticians out there whose business is to go through everything and figure out what is wrong with a car. I am willing to spend some cash for someone to show me what is out of spec.

Has anyone heard of such service or know a diagnostic genious? I feel a lot of enthusiasts can benefit from such thing.

You are asking for the equivalent of "House" for automotive diseases...haven't heard of anyone. Could be a fun new TV show though

 

[LowLife]

Sounds to me like you have a small vacuum leak somewhere......I'm not 100% familiar with these cars yet (just got mine last week)....but my experience with other cars tells me that vacuum might be the problem.

FWIW, the first mod on most hypermilers (guys who need tip-top running engines), is to get a vacuum gauge installed. I'd check all the vac lines to make sure none are split, cracked, or leaking.

Good luck!

 

[gerryvz]

The only MB mechanic who makes "house calls" that I know of is Pierre Hedary in Florida. He is well known for flying into customers' premises and working on their cars at their locale. He is located in Titusville, FL.

http://pierrehedary.com/

Cheers,
Gerry

 

[ivanned]

Haha lets start a show! I'm all for it!

I actually went to MB of White Plains and one of the guys there that I know spoke to the shop foreman and asked him to test some individual components and see which one could be out of spec when hot. They also gave me a MB Club discount on labor so lets see.

I know vac lines can affect the idle, but they will not affect drivability the way I am being affected.

I really hope its a cam or a crank sensor. It would be a piece of cake to swap it.

Gerry I hope I don't have to fly someone here or I'll have to sell my other car to afford this one LOL

 

[ivanned]

I dropped the car to the dealer and the first thing they told me that the car had a code for MAF and it was the MAF that was bad. I told them that I had disconnected the MAF in the past and the drivability issues remain.

From what I understand the car can run without a MAF just fine but it would be down on power. Can any of you guys confirm that? If the MAF is disconnected, can the car be driven normally with small loss of overall power?

I just want to be ready when they try to convince me I have to replace the MAF which almost never goes.

 

[gsxr]

The car should go into a fixed (open loop) mode with the MAF disconnected and it should be driveable. HOWEVER... if your MAF is defective, i.e. sending wrong data to the computers, the adaptation values could be way way off. I am not sure what happens in that case. It's possible the computer goes into fixed mode but using the messed-up adaptation values, which could cause an overly lean or rich condition. Bottom line, I'm really not sure what to expect with your specific scenario.

Didn't Hendy or Fredtga have a good used MAF available...? As you said, these are not a common failure, I'd consider a used one if cheap enough...

 

[ivanned]

So My friend works for MB stealership and he said that the predetermined condition is most likely based on a ROM memory and is a part of the module programming and upon disconnecting the MAF the car should operate at factory predetermined values.

 

[gsxr]

So My friend works for MB stealership and he said that the predetermined condition is most likely based on a ROM memory and is a part of the module programming and upon disconnecting the MAF the car should operate at factory predetermined values.

That's what I thought... but as mentioned above, the adaptation values may still be used, as those are stored in memory unless manually cleared.

The guy running the scanner can check the adaptation, in general anything more than 10% adaptation in either direction is suspicious. It almost always adapts leaner (i.e., 0.99-0.90 would be the 1-10% range), it's pretty rare to see adaptations richer (1.01-1.10 would be 1-10% rich). Earlier LH modules will trigger a fault code on the DM when adaptation exceeds approx 15%. This was later changed to allow something like 30% via newer software.

They can also check actual values from the MAF. I really, really don't like when they only base diagnosis off codes. My BIL had his W140 door closing assist diagnosed at the dealer a few years ago and they told him it needed a new lock assembly for ~$400 plus a few hours labor. He declined and lived with it not working. I recently investigated and found that while there was a code present, the actual problem was a leaking vacuum actuator. A new actuator for $80 fixed it. Had he let the dealer do the job, he'd have been $750 poorer and still not had the closing assist working. Which is why I don't trust techs who don't fully investigate the issue. They should be able to tell you what the MAF readings are in kg/hr, and also what the readings SHOULD be. If they can't tell you that, they haven't done due diligence.

 

[ivanned]

Thanks Dave I will be after them. And if all else fails I've heard the drive to Idaho is pretty cool

 

[ivanned]

Update: dealer tried the MAF and it is not the MAF. They mentioned secondary ignition system. I haven't even hear of that.
I will speak to them soon to find out what is their next move.

 

[gsxr]

Secondary ignition system means the high-voltage side... coils, caps, rotors, wires, plugs.

Primary is the low-voltage side, i.e. the EZL and wires to the ignition coils.

 

[vexed]

Secondary ignition system means the high-voltage side... coils, caps, rotors, wires, plugs.

Primary is the low-voltage side, i.e. the EZL and wires to the ignition coils.

Are coils an issue on the M119? I rarely hear about them failing.

 

[gsxr]

Are coils an issue on the M119? I rarely hear about them failing.

Same here, they don't often fail totally (i.e., stop working). However a failing coil can draw excess current and destroy the EZL. Mercedes will not warranty a new EZL unless new coils are installed at the same time.

Jono says new coils can help eliminate the occasional idle hiccup for the ultra-smooth idle. I think he replaces them proactively if they are original....?

 

[vexed]

Same here, they don't often fail totally (i.e., stop working). However a failing coil can draw excess current and destroy the EZL. Mercedes will not warranty a new EZL unless new coils are installed at the same time.

Jono says new coils can help eliminate the occasional idle hiccup for the ultra-smooth idle. I think he replaces them proactively if they are original....?

Thanks, part of the reason I asked was this thread at BW-you must have seen it.http://www.benzworld.org/forums/w12...080-help-pls-1994-e420-rebuilt-longblock.html I think some of the "advice" he is getting is bad and leading him in the wrong direction. But maybe his EZL/coils did go bad. Since the car will start, run and die my money is on something else.

 

[gsxr]

That poor guy. Yikes.

 

[gerryvz]

Thanks, part of the reason I asked was this thread at BW-you must have seen it.http://www.benzworld.org/forums/w12...080-help-pls-1994-e420-rebuilt-longblock.html I think some of the "advice" he is getting is bad and leading him in the wrong direction.

Bad advice is an everyday occurrence at Benzworld.org, particularly in the 126 forum there.

The E500E uses the same coil (except two of them!) that the 560 models use (M117), and this is best obtained new on the aftermarket, Bosch, from places like AutohauZ [or Amazon], not MB/parts.com

 

[ivanned]

So they think it is wires. I am thinking they may be right. I would have sworn that they were changed, but there's no record, which means the wires could be original. I will get a Bosch set from autohaus. Are the OEM bosch or beru?

 

[gsxr]

I forget which, but there's a guy on the forum who sells pre-cut wires in pretty blue or red (Beru, IIRC) that you use with your existing ends. You should also test the plug boots, they should measure ~2200 ohms, ±10% or so. If the ends check out you could just replace the wires themselves. A complete new set wouldn't hurt though.

 

[vexed]

That poor guy. Yikes.

Thanks for jumping in. I hope he reads the codes, but already he has thrown a lot of parts at it.

 

[samiam44]

If the wires read above 2.2k ohm replace offeing wire or connector.

 

[ivanned]

yep will do so. It could be tricky though because it is inconsistent. I think resistance may increase or the wires may short somewhere but only in certain conditions. I guess values change with heat. In any case, the dealer is trying new wires to see if they will solve the issue. I'd rather them try a few parts and charge me 2-3 hours diag fees then me throwing thousands into parts trying to solve the issue. And who knows, it may not even end up being wires. I'm still waiting. Also it may turn out that the replacement EZL the car got may be the original one and it is possible the PO's previous shop had the EZL either rebuilt or lied to him about replacing it. In any case they charged him almost 4gs for it.

 

[gsxr]

I've never heard of an EZL that worked fine when cold, but failed when it heated up. I suppose it's possible, but not likely. Even less likely is to have two of them doing the exact same thing.

 

[gerryvz]

EZLs either work, or they don't. There's no graduated failure depending on temperature.

And generally, EZLs either die totally (i.e. engine no run) or partially (i.e. one half (one bank) of the engine will not run).

The latter happened to me back in early 2009.

 

[ivanned]

Update:

Ruled out: wires, EZL, MAF

These are the parts that the dealer swapped and made no difference.

One thing they noticed is that the LH module which was replaced in 2006 was replaced with the wrong one. The service guy said the module enclosure did not even fit the special removal tool they have.

I don't feel like an idiot any more after I thought it was wires only. It seems the problem goes deeper.

I will keep the updates coming.

 

[gsxr]

weeeeeeird. What was the part number of the LH module? I'd love to see a photo of how the enclosure did not match their removal tool. That sounds awfully fishy to me.

 

[ivanned]

I asked them for a part number and a photo lets see what I get

 

[gsxr]

Dumb question - the car had been running OK for a while since 2006, after the "wrong" module was installed, correct?

Also, there are a few LH modules which no longer appear in the EPC, which are correct/valid for the car. So, it depends on why they are saying it is "wrong". If it's a 4.2L module, yeah, that's wrong. But if it just doesn't match what the EPC says should be there, that doesn't necessarily mean it's wrong. Need a part number to find out!

 

[ivanned]

Yes it appears the car has been ok since i bought it in 2011. It has always had a millisecond stumble at WOT when hot though. It was never a loss of power.
I am wondering if a defective cap/rotor could be at fault. It happened after the caps and rotors were replaced but it maybe a coincidence.

I wish we had the tools and parts we needed to test this but I guess only MB has the recourses to swap parts and see if they work.

 

[ivanned]

What about clogged CATs could that affect the ECU?

 

[gsxr]

What about clogged CATs could that affect the ECU?

It's possible. But as a general rule, partly plugged catalysts will only reduce full-throttle power. It wouldn't harm the ECU and should have minimal effect on adaptation values.

Massively plugged catalysts could prevent the engine from running more than a few seconds. But that is very, very rare... I've actually only seen that on diesels with catalysts - never heard of it on a gas engine.

Neither scenario should cause an intermittent misfire.

 

[500AMM]

Yes it appears the car has been ok since i bought it in 2011. It has always had a millisecond stumble at WOT when hot though. It was never a loss of power.
I am wondering if a defective cap/rotor could be at fault. It happened after the caps and rotors were replaced but it maybe a coincidence.

I wish we had the tools and parts we needed to test this but I guess only MB has the recourses to swap parts and see if they work.

Ivan, that make some thoughts. Why was the caps & rotors replaced? Should you try swapping the old parts back? (supposed you still have them)

Due to the fast verdigris build up on the contact points inside the caps they'll cause stumble idling. And if they are really bad they can be replaced, but then they must be REALLY bad with burnt down contact points etc.. The contact points have a bad appearance anyway after a year or two driving, so many thinks replacing is a miracle cure. The truth is that with proper cleaning they can work fine for a long time again, or at least for comparing before & after when detecting troubleshooting.

 

[ivanned]

Another update: the shop foreman is putting hours into figuring the car out. He has ruled out so far:
MAF
WIRES
CAM s.
Crank s.
EZL

a bunch of other things that the service advisor could not explain.

He has narrowed it down to an electric fuel delivery problem involving the fuel module CAN communication or injectors. During misfire my impression was that the CATs were getting hotter than normal possibly indicating no fuel or lean condition to some or all injectors.

He will check all connectors with an oscilloscope and narrow the issue down.

Arnt, I did clean the caps and rotors and no change. I do not have the old ones unfortunately, but idle misfire was there before the new ones were installed.

I will try to get the full story once this is resolved and hopefully post some test results as well. The way I see it if it turns out to be an obscure problem, hopefully all will benefit.

 

[LowLife]

Is there a way to adjust the fuel mixture on these engines like there is with the V6 300E models?

 

[gerryvz]

Should also check out the physical fuel delivery -- pumps, filter, fuel rail, FPR, etc.

 

[gerryvz]

Is there a way to adjust the fuel mixture on these engines like there is with the V6 300E models?

In a word, no. Everything's computerized with the LH system, unlike with the KE-Jet systems. This has both advantages and disadvantages, but the advantages are higher.

 

[ivanned]

I agree I had already checked fuel pressure during misfire and it does not drop. Filter is new. FPR has been replaced relatively recently ... the guy was saying they lost communication with one bank cylinders when hot but the advisor could not explain more.

 

[KarlC]

Should also check out the physical fuel delivery -- pumps, filter, fuel rail, FPR, etc.

Gerry, I just spent about 30mins on the phone with Robert Fenton, he speaks highly of you by the way. During all the 500E chat he said he had one that had a ruff idle and would skip a beat, he replaced both fuel pumps and all was good.

 

[gerryvz]

Why I suggested the pumps, I've had to replace them on two of my cars. Best place to get OEM Bosch pumps (last time I checked about 30 days ago) was via Amazon.com.

 

[Jelmer]

Jumping back in this thread, this is a video of what my original question was about:
[youtube]ibMxFCo97b0[/youtube]

In the span of only 27 seconds you can clearly hear the rpm dropping and the engine shaking, you can also clearly see the oil pressure gauge dipping a few times.

Although I promised myself not to spend as much money on the car this year as I did last year, I think of finally getting back in to tackle this problem. My first steps would be replacing the coils, and possibly also the fuel pumps, "just in case"...

 

[500AMM]

Jumping back in this thread, this is a video of what my original question was about:
[youtube]ibMxFCo97b0[/youtube]

In the span of only 27 seconds you can clearly hear the rpm dropping and the engine shaking, you can also clearly see the oil pressure gauge dipping a few times.

Although I promised myself not to spend as much money on the car this year as I did last year, I think of finally getting back in to tackle this problem. My first steps would be replacing the coils, and possibly also the fuel pumps, "just in case"...

+1 on both Jelmer.

Both the fuel pumps and ignition coils can fail gradually. The coils can even be affected by the heat in the engine bay.