'91 W126 500SE Ignition module help

[Takernz]

I'm posting this for my fellow MB owner who's needs help to figure out what's the correct no. of 500SE ignition module? the story is this; back then, his car wasn't starting, so he replaced the module without knowing that the current module is from another model car. Now, it starts but it seems not getting enough revs from the engine, the engine cuts to about 3000 rpm instead of 6000. Worse, acceleration is sluggish and fuel consumption is very high for a 5L V8.

[TJ 450]

There were a number of different modules depending on where the car was sold, and whether or not the car has catalytic converters etc.

Did he happen to note the specs of the old unit?

Tim

[s class]

No way to guess without a VIN and engine number. 

[Takernz]

@TJ450: the 500SE has catalytic converter,air pump, EGR, cruise control, same as the US smog equipped but definitely euro model. And I'll ask him about the old module
@sclass: I'll ask for VIN number next time we'll see each other, I forgot to mention

BTW, Is the W126 is equipped so called "LIMP MODE", if something else broke.

[TJ 450]

Not sure about the limp-home mode, but it probably does. That part of the system is computer controlled.

Tim

[Takernz]

Not sure about the limp-home mode, but it probably does. That part of the system is computer controlled.

Tim

I think, after the module replacement, his car is already in LIMP-HOME mode because of wrong type of module it replaced. This maybe the causing all the trouble (engine rev early cut-out, sluggish acceleration and crappy fuel mileage). I drove the 126 (with the owner's consent) for 120 kms and consumes fuel about 30 liters so , that's about 4 kms/liter!

[WGB]

The last two years of the 126 had updated engine management systems that were totally different to the earlier models and more related to modern m,anagement systems.

As far as I know they are totally incompatible with earlier systems so the fact that the car runs at all is a miracle.

Suggest you find a Mercedes Specialist who knows this model and sort it properly or it is just a piece of junk.

Bill

[TJ 450]

That's right, CIS-E3 with knock sensing capability. No wonder it runs so poorly, the ignition timing is probably fully retarded.

Tim

[Takernz]

That's right, CIS-E3 with knock sensing capability. No wonder it runs so poorly, the ignition timing is probably fully retarded.

Tim

to whom you referring to sir, me or Bill?

[TJ 450]

The reply was tending towards Bill, though it is also general.

Tim

[Takernz]

here's my fellow MB owner's info

chassis no. :           WDB1260361A543188.
engine no.:             117965 12 029890
Transmission no.:   722356 03 367984

he also needs help finding the correct wiring diagram for his W126.

Thanks fellows!

[KenM]

According to the EPC the ignition control module for that car is part number A002 545 26 32. There is also an idling control module, part A002 545 40 32. Can't help with the wiring diagram,

Cheers,

[Takernz]

@kentm: Thanks mate! where is the idling control module located? can you point it out for me? Good thing you mentioned the idling control because the 500SE's idling is rough almost stalling.

[KenM]

Don't know whereabouts in the car these modules are located, I haven't got a 126 but the epc shows them in the engine bay I think.

[johnq72]

Evening gents, noticed this post about ignition modules on W126, idle speed module is located under carpet with another ominous black box in passenger footwell in my car. Mine is uk right hand drive though.
I also have 1989 500SEL that just failed to start with no apparent cause, is this a common problem? and where do i start looking? crank sensor and coil both check out but no impulse to coil. Does anyone recognise this symptom, or have a section of the wiring diagram ? vin number is WDB1260372A27055, any help would be greatly appreciated as this has been going on for 3 months, and I hate being without it