E220 Hesitates and shudders while accelerating

[Gyri]

My 1996 Petrol E220 W124 (HFM type) engine (111.960) every now and then annoys me while accelerating. This happens once in maybe 3 KM of running, with or without the aircon ON. When it happens, it basically for a second doesn't respond to the accelerator input and then lunges forward jerking-ly. I have found that when it happens, I can get over it by depressing the clutch pedal and then pumping the gas pedal fully a couple of times. It then resumes to running normally, until maybe a few KM later. This can happen during gear shifts or while giving throttle inputs from steady speeds.
OK, the story before this is that the car used to stall much like W124 s described in many other threads. I had MB authorised men have a look at it with their diagnostic tools, all in all they had my car for a month and a half.
First it was the Engine wiring harness which was re-insulated by them for almost 1/3rd the cost of a new part. Then all filters (air, fuel, oil) were replaced. Fuel tank cleaned, New throttle cable, new spark plugs, new fuel pump (the old one was whining, but load and delivery test showed it performing well). OVP relay was visually checked and it was the new SIEMENS one, so that was ok. Throttle body was cleaned. The diagnostic kit showed all the sensors to be working fine. Well, the engine doesn't stall anymore and I haven't noticed any abnormal RPM hunting off late, but then every now and then she behaves as though she moves on square boots :roll:
Ran the tank through a can of injector cleaners, No luck!
Naturally, MB gave me a list of components to change, which pretty much excluded only the body panels. It was time for me to take my car and leave.
So here I am.
Any and every bit of help would be very much appreciated!
Thanks in advance!!!!
BTW, my car has run 41000 KM. :evil:

 

[OlafMaxwell]

Check the fuel tank venting system.......make sure when you unscrew the fuel cap you do not get too much air being sucked into the tank, could mean the engine is being starved of fuel. Is there any consistency, does it happen only on or just after long journeys? This won't show up on the diagnostics.

 

[Gyri]

Hi, This is the first response I have received in this forum, so thanks!
In terms of consistency, the only thing I can think off is that it starts happening only after the enigne is warmed up, say when it get to 85c on the gauge, that's about 5-10 minutes drive from the parking lot. From there on, as I mentioned earlier, it could happen once every 3 KM.
About the tank, where is the venting lines/system located, I presume everthing in that department would be ok since the tank was cleaned, filter and pump changed, but now that you point out, it's worth a look.

 

[Terminator]

Did they check the catalytic convertor and lambda probe? Worth getting these tested if not.

 

[Gyri]

They had this computer called "Startac", from which they could, I guess, monitor all the sensors and fault analysis and they did tell me that both the O2 sensor were ok. Maybe they presumed (as I did as well) that the CAT would be alright as the car had done just 40000KM. I'll try and have them run through those again. What else should I check, if and when I get my next oppurtunity to have them diagonise it. Also where is the fuel tank's pressure vent!
Thanks !

 

[Mikesmerc]

My old 230E 124 has always had a whoosh of air into the petrol tank when I unscrew the cap and my brothers 190, I presume this is normal. Im afraid I cant help you locating the vent Gyri
Regards
Mike

 

[Gyri]

I have noticed the "whooosh" in a lot of cars. Don't recollect that happening in my E220 now or any time before. Anyway, will flip through the Haynes and MBOA W124 manual again for the presure vent. One of the problems with these two repair manuals is that, they don't address the HFM type (M111) engine management system in any detail at all. They just mention them for a couple of pages, period!
Glad to have you folks help me out! Hope is really the essence to move on and in this case it's hope to find the cure, or else could have dumped the white elephant a long time ago.

 

[Terminator]

They had this computer called "Startac", from which they could, I guess, monitor all the sensors and fault analysis and they did tell me that both the O2 sensor were ok. Maybe they presumed (as I did as well) that the CAT would be alright as the car had done just 40000KM. I'll try and have them run through those again. What else should I check, if and when I get my next oppurtunity to have them diagonise it. Also where is the fuel tank's pressure vent!
Thanks !

When my 1991 300CE had a similar problem the specialist's diagnostics did not pick up the faulty lamda probe which only generates a fault code if it completely fails, not if it continues to work all be it impaired. In my case the cat was rattling and extremely hot, no doubt caused by the break up of the internal monolyth, in itself probably caused by the faulty sensor. In my case the faulty sensor was 'diagnosed' by a 'Tune-Up' Engineer. In the end I had a cat bypass carried out by Longlife Exhausts (Recommended) and a new lamda probe fitted, which cured the problem. Get your engineer to interrogate the lamda probe and check that it is working within tolerances. I was lucky as my car was built before cats were mandatory so I could dispense with it.

 

[Gyri]

OK, if they can't pick up an issue with the Lambda probe with the "Startac", then I am going to have to just change it by default. In vehicles with CAT, are there two lambda probes, one before and one after the CAT? Any simple checks on finding out which ones going South?
Mine is a 1996 E220 (M111) engine with HFM Engine Management system.
Thanks for your input.

 

[Terminator]

OK, if they can't pick up an issue with the Lambda probe with the "Startac", then I am going to have to just change it by default. In vehicles with CAT, are there two lambda probes, one before and one after the CAT? Any simple checks on finding out which ones going South?
Mine is a 1996 E220 (M111) engine with HFM Engine Management system.
Thanks for your input.

Sorry but unsure whether yours has one or two lamda probes, mine just has the one before the cat. I would get the probe tested first rather than just replacing it as the MB lamda probe part for mine was about £90 all in.

 

[Gyri]

Just thought I'll keep everyone updated. I managed to locate a friendly dealer, who after a lot of convincing has agreed to lend me a new throttle body to try out in my car. I did try to milk him for an air-mass sensor too, but then he didn't have one in stock. Guess he was worried, if I'll ask him to lend his house too. If everything goes well, I'll do the swap in a week's time or less.
I read in a few posts that throttle bodies tend to fail quite commonly when there are issues with wiring harness, which I did have. Check out http://www.bba-reman.com/throttle_body.htm . While I do suspect a lot of other commonly failing components such as O2 sensors, CAT choking, Air MAss sensor, Purge valve, spark plug resistors and coils, the symptom isn't an engine cutting out or a misfire as in an electrical disconnection, the car idles well, although it jerks on small throttle openings. So maybe, just maybe it isn't an electrical/ignition related issue/component.
With regards to improper Airmass Sensor ( which normally shows up as "check engine Light" and not so far in my case), O2 sensor, purge valve or bad injectors, I should be having some cold starting problems (none so far, fires up immediately) and sluggishness during acceleration (not so, she accelerates well). This week, I'll get my fuel consumption figures when I tank up the next time and also run a "Pollution Control" test (that's what we call it here in India). These two will further give me something to chew on.

 

[Gyri]

A wise man somewhere in one of the forum topics mentioned that if someone nails their problem, the least they owe the folks on the boards is to mention the details that helped solve their issue(s). I agree, as there are many topics that end without a note on whether the problem was solved or not. SO,

I changed the throttle body (~ USD380) and this solved the problem. I have driven the car (about 200 KM) in various conditions since, hot weather, early mornings, rainy conditions, heavy traffic and long highway cruises, no idling problems, no hesitation during acceleration, no stalling. It took me 45 minutes to change the throttle body. Should take less for an experienced DIY. Just remember to disconnect battery before attempting this. One problem I faced was that an "o" ring was missing in the interfacing area with the casted-metal inlet manifold. Unfortunately, I didn't have a spare one and had to use high temperature RTV sealant in that area. Apart from this, I had some resin coated fibreglass sleeve, which I used to wrap the throttle body?s connector cable, and secured the same with heat resistant adhesive tape. This is purely a precautionary measure to prevent the cable from turning brittle from heat again.

For all W124 owners, I strongly recommend that they check their wiring harness during all service routines. If found brittle or damaged, replace them. They are expensive (~USD 700, the lowest I have found so far) and the MB people might charge stiff on labour. If you want to do it yourself check
http://www.mercedesshop.com/wire_harness/1994_e320_harness.htm
. One thing to consider while changing is that the new wiring harness might not be of a better grade, so it too could go bad in 40000 kms or so. Hence, before changing, as suggested above, wrap the wires with resin coated fibreglass sleeves of suitable diameter and secure them with high temperature adhesive tapes. Don't go over-board and wrap them too much as they might end up not being flexible enough to go through all the bends. Bad wiring harness spoils many electronic components such as sensors and actuators long before the shop-computer can properly diagnose them.
Here is another suggestion for those owning a W124 with HFM fuel management system and unhappy with the info available on Haynes W124 manual or MBOA W124 manual. Buy the Haynes C-class 1993-2000 manual. The engines covered in this manual are HFM type and hence give you more related information.

I really would like to thank all you folks for your suggestions and also for the various topics that have already been posted earlier.

 

[Richard.Wilson]

I seem to be having some gremlins which point to the wiring loom also. I've got an intermittent missfire, which seems to effect either of the front two ignition coils. it either misses slightly on one coil, or aditionally one coil shuts down completely. swapping the coils about does no good, nor did a new one. Changes each time I start it up!
It seems possible that it's bad wiring connections, but this thread makes me wonder if it's the loom....
Does anyone know the part number of the dodgy loom and it's replacement so I can check mine?
Or another suggestion as to the missfire?
Thanks

 

[Geoff_Slade]

Out of curiosity when did MB start putting the poor quality wiring in their cars? I've got a 93 W124 300D (registered early 93 so could be a 92 build). One thing with this forum is it starts to send you paranoid when you read all the problems but I suppose there are far more cars that have none at all (hopefully :!: :!: ) that we never hear about (well that's how I keep my sanity :lol: :lol: )

 

[Gyri]

Geoff, the diesel vehicles are known to be very reliable, you just have to ask the German taxi (cab) drivers or look at their odometers, now we are taking Benz. Sadly it's not the case, with the Petrol vehicles, where presumably more electronics crept into the engine bay. From other posts, I gathered that the reason for wiring loom failure is because, MB used a special grade of plastic insulation that had to comply with environmental regs. Don't know how far that is true, but it does degrade fast. These seem to happen from 1992 on the W124 models.

Richard, what year and model is you vehicle? Please check near the fuel injectors for bare copper wires criss-crossing (you could move the insulation sleeve a little back to expose this), that could be a problem. Also it's important to identify the problem as either a mis-fire or a fuel cut-off. In my case, for the first few months that I suffered, it did appear as a mis-fire. I too checked the coil packs as they are also prone to failures. It's only when I figured that the symptoms were fuel cut-off, that I managed to make headway into solving the issue.

Good luck!

 

[Geoff_Slade]

Gyri. Thanks you've put my mind at rest. I know the petrol engines give better performance but looking at the posts on the forum it would appear that they have more problems (more to go wrong on them I suppose) so diesel has its benefits. Just hoping that my car was manufactured before the environmentallysound wiring started being used . Or is the dodgy wiring more of a problem with petrol because of more wires (must admit I haven't seen any diesel owners posting electrical issues). Does this also affect wiring to ancilliaries (windows, doors mirrors etc etc). Sorry there's me saying you've put my mind at rest (which you have) and then I ask more questions :!:

 

[Gyri]

Geoff, from what I have heard and read, wiring degrades due to heat and for that reason they don't happen elsewhere other than the engine bay. Typically it happens to cables that run very close or over the engine.
If you have a realiable and clean diesel W124 (specially pre 97), it'll remain that way for very very long, with just scheduled maintenance. The best part is the cost of spares (from the right source) and if you are a basic DIY, ...they are very reasonable and considering the reliability, great value for money. I bring this up again, check with a German taxi guy or look at his vehicle odometer. My friend has a 94 Diesel W124 Estate, it is still a status symbol and works out cheaper that modern Japanese mid-sized cars. He finds it very hard to accept my verdict on MB loosing sight on Reliability. So, if you haven't already, get the haynes workshop manual for the W124, if you don't have a problem it's fun to go through it and if you do, it's reassuring that you have help. Atleast helps you gauge a mechanic's estimate or to know what he is talking about. I have got one for all my cars.

 

[LNM]

Gyri

I hope and pray that you + yours escaped any mishaps. I've just noticed your location.

 

[Richard.Wilson]

Hi again hope you all had a good holiday,
Gyri, mine is a November 94 registered W124 E320 Estate RHD
Peeling back the "new" looking woven tape from some of the engine sensors reveals cracked insulation and bare copper visible, so I guess the loom is toast. I've had no joy with the MB dealer as far as whether this car had the loom "repaired", but I think someone has re-insulated it at some time ( doesn't help if the cables are breaking up, but might have been a temporary fix) :cry:
The looms are damned expensive here in the UK, seem to be £450>£550 depending on the model.
Does anyone know if there is an improved part or am I fitting the same crap quality again? any info on UK part numbers would be appreciated
Thanks

 

[mjtray]

The original looms were made from a new type of bio-degradable plastic that degraded too quickly!!.....cars in hot climates tend to be effected more that those in Northern Hemispheres.

Many many owners in the States have had to replace their looms.

I believe that the replacement looms are made of a different type of plastic.

The price you have been quoted sounds inline with the prices US owners pay which is $800-900