Thanks for the thorough testing and analysis.

I'm interested in retarding the timing on my '88 190E 2.6 in order to achieve a better passing margin on my California emission test, which is done on a dyno at 15 and 25 MPH in second gear (manual trans).

I was hoping that removing the resistor and shorting the plug would retard the intial timing from its 9* setting, but you indicate this is not true. Can you verifiy?

I believe my relatively high emissions are due to too low EGT as IR gun measurements indicate only about 500* at the exhaust manifold and lower entering the main converter on a fully warmed up engine after several minutes of idling. My hunch is that the idling causes the converter to cool down to the point where is it not as efficient and this causes relatively high emissions on the first test (15 MPH), but since the 15 MPH test is done under relatively high load, the converter heats up and the 25 MPH test has much lower emissions relative to the 15 MPH test.

Retarding the timing at idle or any operating speed will increase the EGT, but even if shorting the plug doesn't change idle timing, it should reduce the timing during the test, which should heat up the converter faster.

My duty cycle is in the correct range and all indications are that there is nothing amiss with the engine or control system. Anecdotal evidence indicates that a lot of other 103 owners are seeing high emissions. My hunch is that it's an EGT issue, which could probably be changed by retarding the timing, especially at idle.

The idea of shorting an electrical is a scary thought, so I want to confirm that shorting the plug did not cause any harm and that it did not change the initial timing. Thanks!

Duke