Some of you may remember the hesitation problem I was having at around 200RPM with my m103 engined Brabus 3.6. While trying to eliminate it I:

Had the ignition system checked on a scope, it was fine - no change
Changed and recalibrated the bosch air flow potentiometer - no change
Had the fuel distributor recalibrated, it was underfuelling - no change
Changed the coolant and ambient air temperature sensors for the KE-Jetronic system - no change
Changed the OVP relay with a new one I had - no change
Replaced the fuel pressure regulator - no change

I rebuilt the engine (bored a new block, new rings etc, had camshaft reprofiled and rockers refaced, valves re-seated etc.) due to excessive oil consumption half hoping that the problem would disappear when it was reassembled, it was still there . My duty cycle was at 40% showing no faults as my car is a non-cat, RUF model. Interestingly, the problem dissappeared when I removed the CTS connector, thus getting rid of the electronic part of the KE system. This makes the system run leaner as the EHA valve does not operate (this confused me as I initially thought that it would revert to a richer mixture). My car failed its MOT due to CO content above 10%! This has now been adjusted down to 1.4%, about right for this car I do believe.

A Brabus plaque for the engine states that ignition code N on the R16 resistor must be used (why?). However, advancing the timing to 2 (sequence is S 2 N 3 4 5 6 7) gets rid of the hesitation problem. Meanwhile at S it feels smother but less powerful hence I have kept it at 2. I have checked the basic cam timing and moved the cam gear to its alternative position to make it line up perfectly with its alignment mark at TDC. I have turned the engine over twice by hand and rechecked this to make sure that the basic timing is spot on. The car does however, feel more aggressive in N once the 2000RPM barrier has been surmounted.

Additionally the car does have a lumpy and low idle at just over 500RPM, sounds and looks like its missing.

Any ideas as to why position 2 "solves" my problem, whatever my problem is? The car used to run perfectly fine in N (a couple of years back now though). BTW I run it on 99RON fuel religiously. Also any idea how long these blocks take to run in?

2 is retarding the timing, S is retarding timing even further. If Brabus requires it to be at N it means they require you to use 95 RON. It doesn't make sense that retarding timing is necessary if you are running such a high octane as 99. I mean if you were running 90 RON I would say aha thats the problem. Very weird.

This is a guess, I don't know my knowledge is basic so here goes...what if the car has an over advanced timing causing knocking despite the high octane? So retarding the timing has helped it. Its possible that setting to factory doesn't work and you have to set it of slightly. Just guessing

I had the exact same problem with my 2.5-16, and found that retarding the EZL plug eliminated the hesitation problem. However my manual states the car should always be on S! I too changed most things just like you...
After many years of pulling my hair out, the main dealer finally pinned it down to a faulty ignition control module! It solved all problems...

zakh - The ignition control module being the module that sits on the wheel fender and determines the spark timing using the R16 resistor value and inlet manifold vacuum? Did your car have a low idle too? I do remember trying one at a breakers a while back but it's no harm to give it another go.

yal - S and 2 are more advanced than N, as the numbers increase so too does the retardation. I do have the feeling that you're right that I'm somehow masking over the underlying problem though .

Thats exactly the one, de[ending upon you car there will be three connections to it along with one vaccum connection.
Best not to get one from a breakers. You can't be 100% sure its good?

My idle was ok, but i had a fair few issues...This little box is the heart of the ignition system. Unfortunately though a new one costs a pretty penny. But, buy one from a Bosch dealer, it will be cheaper.

I've just remembered something. When I transferred the engine over to this chassis I did not transfer the ignition control module with it. I implicitly assumed 103.983 RUF engines would have the same modules but looking at the mercedes EPC tells me this is not the case. Now my current chassis has p/n 0055458532 installed, I'm not sure what the original chassis had, I hope mercedes can tell from the chassis no.!

Does anybody know what difference these p/n have? I'm guessing they have slightly different ignition maps for the same R16 values which perhaps explains why my car runs better at "2" than the "N" stated on the Brabus plaque. However I didn't think that more retarded iginition could cause problems, only that advancing it too far could? I'm confused!

I know for the 560's the RUF/ECE cars had their own EZL's and KE control untis so I would swap those modules over..@ least is easy and you already have the part!

I didn't see any mention of a fresh O2 or fresh injectors..but based on what you have done thus far I'm wagering they were tended to, no?

Jonathan

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Jonathan Hodgman
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I swapped the KE control unit over but overlooked the EZL unit. Unfortunately I sent the car to scrap after I took what I thought I wanted from it, I'm not sure where it went either!

The car doesn't have a catalytic converter (neither did the original chassis) and so no O2 sensor. The injectors are old but were checked by the gentleman who rebuilt the fuel distributor and they were fine.

I've checked the part number that is currently installed and according to the EPC (& Mercedes), its for a catalyst equipped car. The part number for my engine, as checked by Mercedes via the chassis number, is 003545 ending in 1432 or 1532 or 4332 or 4732. Does anybody know how different the maps between the cat and non-cat cars are? They retail for over £1,300 ($2600!), I've got to find one from a breakers.

Hey man, PM me your details...
Are you based in the UK?

I might be able to help you

Okay, despite insisting on a 003 part number the breaker couriered p/n 0065457632, a newer Siemens made unit but one of the Retrofit/Catalyst parts. It was too late to have a moan so I quickly swapped it over and set R16 back to "N".

After a blast on the M40 I can confirm that the hesitation is gone . Top marks to zakh! However I'm still convinced that it is the wrong part number as the EPC on this page shows. Will getting a 003 p/n further improve my performance? Having found none anywhere I'm sure that Mercedes did fit non-003 p/n to non-cat cars which is confusing. Any experts on this?

Also does anybody know the proper conduction paste to use when installing these units?

If you found an EZL that works for your car that is not the correct p/n COngrats! Many engines have a specific EZL p/n and no other will work correctly. Say, the 2.3-16v 190E EZL. It is for only that engine for only 2 years in the US. It is HARD to find a good used one and a new one runs $1800 or more at MB. Glad you found one that allows the engine to run better. Might still look for the correct p/n but be happy with your find.
Always use the EZL that came with the engine, they are very specific even for the same engine in different years. Good Luck, Cheers.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Cheers chrenkel. I'll call another breaker tomorrow who may have one (a 003 p/n) and order it just to check if there's a difference although, with this one running smoothly it may be hard to tell. What symptoms did yours show with the wrong EZL? Have you tried searching online breakers in the UK such as dronsfields.com for yours?

Now, is this conducting paste that it should be installed with the same stuff that connects CPUs-heatsinks? If so I assume that I should clean the bottom of the control unit and the fender and then apply this paste and install? I will buy something like this that doesn't conduct electricity but is a great thermal conductor if this is the case...

I will be changing my coil, wires, distributor cap, rotor arm and plugs later this week both to protect my "new" control unit and to hopefully get rid of my low/misfiring idle.

EDIT: Having scoured breakers yards up and down the UK I have had it confirmed to me that many non-cat 300Es left the factory with EZL units that are "inapplicable to retrofit/catalyst vehicles" as NO UK breaker had the 003... units but yet had lots of 300E 12V modules. I am left to assume that the "only applicable to retrofit/catalyst vehicles" are basically compatible with all cat and non-cat 300Es but that the "inapplicable..." ones are ONLY for non-cat cars. Since I can't get hold of an ""inapplicable..." non-cat one at a breakers I can't test to see if there is any difference.

I am sure a breaker in the UK would have the EZL I need, But, I have had a hard time contacting them and getting them to ship to the US. The P/N I need is probably on many of the 2.3-16v in the UK since they were Manufactured all the way up to 1992 or 93 in Europe. The part number I need is MB 004 545 57 32 or MB 004 545 59 32 There are not really any Bosch dealers here in the US like there are in Europe. It is the dealer or the breaker here. If you can figure out how to get one of the EZLs to me please let me know, I have had little luck getting one found and shipped to the US.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Oh, ya, the conducting paste they are talking about is just a heat conducting paste. About anything that is for heat conduction would work. The paste they use for the CPU in a computer would work fine. The EZL puts off heat and they want you to use the paste and the metal fender apron as a heatsink to dissipate the heat. Your cpu paste idea would be just fine.

__________________
Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

Thanks for clearing up the conducting paste issue. I'll have a word with the breakers here. If they're not prepared to ship to you then I'd be happy to forward the package on for you. I'll let you know the prices via pm but I expect it'll cost me around $200-250 to get one as that's what mine cost.