1989 300E - 36,000 miles

I currently reside in Canada and am obligated to submit to an emissions test every two years. Upon having the vehicle tested today, it failed the HC and CO test miserably.

The testing facility ran the vehicle so that the engine would be warm during the testing period. The car was not run on a dynometer.

The test was segmented into two components - 2500 RPM and IDLE RPM
The results were as follows:

2500 RPM

HC ppm Limit 200 Reading 24 PASS
Co% Limit 1.00 Reading .04 PASS


IDLE RPM

HC ppm Limit 200 Reading 264 FAILED
Co% Limit 1.00 Reading 5.13 FAILED

I am suprised that it ran so well under load but failed so poorly during the idle component.


Additionally, another peculiar trait that has manifested occurs when I release the accelerator pedal and coast (ie. approaching a corner ) under 2000 RPM while driving. The engine surges between 1000 and then back to 2000 RPM for 3 times - then the surging stops. This happens during cold or hot conditions.

I wondered if there was a possible connection. Other than that the car idles at 700-750 RPM and drives well.

As mentioned in a previous post, when I bought the car, I encountered some starting problems and elevated Nox readings which resulted in failed emissions test. After replacing plugs, rotors, cap and cleaning the injectors, the ECU was finally replaced (used unit). The car passed the emissions test.

Any assistance would be appreciated as it has been most frustrating.

Thank you.

Keen