Retarding Ignition Timing (to improve emissions?)

[stevenstevensteven]

Reviewing the archives and found this excellent post from ann old thread on retarding timing... to improve emissions.

Originally Posted by Duke2.6

...

I don't know where the R16/1 resistor is located on your model. Maybe someone with a 126 can help out. Remove the resistor and replace it with a home made shorting plug - like a short piece of 12-gage wire with the exposed ends folded over so they make good contact with the pin receptables.

On my car there is a short piece of rubber tubing that connects from the manifold port to the nylon line that routes to the EZL module. This can be replaced with a piece of 1/8" vacuum hose with a slug of silicone sealer that is allowed to set up.

With these temporary mods, the car will feel VERY sluggish at low revs, but the retarded timing will considerably increase EGT, which will help keep the converter hot. The substitute parts can be removed and replaced with the OE parts when you are done with the test. Once you know the drill it only take of couple of minutes to configure and de-configure for emission testing.

Duke

I'm a little unclear on replacing the vacuum hose. Is this just for EGR equipped vehicles, as my '89 M103 is NOT EGR equipped. If it applies to non-EGR vehicles, I'd appreciate it if someone can help me isolate this hose as I'm not certain which hose Duke is referring to here.

Also, do I need to check the timing BEFORE I retard it? What is the ignition timing spec on these cars?

Thanks again.