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Old 05-13-2014, 05:53 AM
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Join Date: Mar 2014
Posts: 15
M103 Manual Swap: Any ECU problems or is it old enough?

Hi everyone,

I've finally collected most the parts needed for my manual conversion.

Just waiting on my flywheel to come in & a clutch kit & i'll be ready to start swapping.

However my buddys have been getting be cautious about ECU problems when it's done. Obviously because of Auto to Manual.

I have been researching, and found information that states OLDER MODELS DON'T NEED ECU CHANGE apparently they already have the "fuel mapping" the engine needs to function with the manual box.

Makes sense, I guess.

The information I got was for a 1992 M103,

My model is 1990 M103.

Will the same apply to me and my ECU just work with the swap?

Any relative info is appreciated,


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Old 05-13-2014, 11:50 AM
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MTI MTI is offline
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Join Date: Nov 2002
Location: Scottsdale, Arizona
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The CIS Control Unit and EZL Ignition Control Unit are the same for manual and auto transmissions, however the Fuel Pump Relay, AC Compressor Relay, Cruise Control Coder and EGR (Speed Control Switch) are transmission specific.
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Old 05-14-2014, 01:56 PM
is thinning the herd
Join Date: Mar 2010
Location: Columbus, Ohio
Posts: 3,338
The 722 that came out is totally mechanical, your ECU is unaware of what is bolted to the back of the motor.
68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i
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Old 05-15-2014, 04:58 PM
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Join Date: Dec 2002
Location: New Castle County, DE
Posts: 1,051
as far as I know the only changes to the engine are removing the kickdown cable and plugging (capping) the modulator vacuum port. Benz being Benz, lots of stuff is different....engine mounts for one. I never noticed any change, assume that difference is slight difference of the damping rate. The switch on the clutch pedal is for cruise control. on my 87 there was no starter interlock. Keep us informed, I'l be doing an M104 conversion soon, interested in how the upshift delay will react when disconnected/plugged.

'79 6.9 Sold (after 27 years of ownership)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'95 E320 sedan
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon
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