W124 missing cat - tuning

[vin230]

Hi

I have a 230CE but seems the exhaust has been modified to remove the cat, and a plain length of tbe has been welded in place. The pre-cats are still there. I has the fuel injection that is adjustabe, so my question is:

Can the gas analyser give a reliable reading without the cat in order to correctly set the mixture?

BTW, the car was like that when I got iot, I would not dream of such a nasty bodge!

Any advice much appreciated.

Thanks

 

[w124coupe]

So you have the adjustment screw accessible through the air filter (with a tamper-resistant plug over it)?

From the factory, cars with cats (and O2 sensor) are adjusted using a meter on the diag socket to set the duty cycle (based on the O2 sensor feedback).

Cars without cats (and no O2 sensor) are set based on CO using an exhaust probe.

If you still have the O2 sensor, then use the duty cycle method - there are some variations so if you want detail, please post the first 5 numbers of your VIN.

 

[grober]

A bit about "duty cycles" and what to expect here. PeachPartsWiki: Mercedes-Benz Driveability

 

[vin230]

So you have the adjustment screw accessible through the air filter (with a tamper-resistant plug over it)?

From the factory, cars with cats (and O2 sensor) are adjusted using a meter on the diag socket to set the duty cycle (based on the O2 sensor feedback).

Cars without cats (and no O2 sensor) are set based on CO using an exhaust probe.

If you still have the O2 sensor, then use the duty cycle method - there are some variations so if you want detail, please post the first 5 numbers of your VIN.

Thanks, I will look those up when I have a moment.
Mine has an O2 sensor and the hex star thingy accessible through a hole in the air filter (anti tamper plug is missing though)

 

[w124coupe]

Thanks, I will look those up when I have a moment.
Mine has an O2 sensor and the hex star thingy accessible through a hole in the air filter (anti tamper plug is missing though)

OK. You need to use the duty cycle method (or a voltmeter).

What's the engine - 102.982?