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914World.com _ 914World Garage _ high exhaust emissions

Posted by: DavidSweden Jul 10 2019, 02:32 PM

76- 2.0- D jet with Pertronix ignition

Car has high emissions at idle but good at higher rpm. Engine warm

Does this indicate that the engine is miss firing one one cylinder when idling and how do I check that its firing on all cylinders?

The engine sounds fine, any ideas as to what is causing the high exhaust emissions?

Posted by: jcd914 Jul 10 2019, 05:31 PM

What emissions are high? CO% HC ppm? Other?

A vacuum leak could create a lean miss at idle that goes away at higher RPM.
Overly rich idle mixture could lean out at higher RPM.

Jim

Posted by: Bleyseng Jul 10 2019, 08:38 PM

Overly rich? Could be the CHT is going......

Posted by: DavidSweden Jul 11 2019, 10:02 AM

QUOTE(jcd914 @ Jul 10 2019, 03:31 PM)

What emissions are high? CO% HC ppm? Other?

A vacuum leak could create a lean miss at idle that goes away at higher RPM.
Overly rich idle mixture could lean out at higher RPM.

Jim

High HC ppm, the idle is about 700

It sound like its firing on all cylinders, I will check the hoses any other ideas?

Posted by: Dave_Darling Jul 11 2019, 05:00 PM

Turn the idle RPM up to at least 900. We usually run it "just under 1000". I think the factory spec is somewhere between 800 and 950 RPM, depending on the exact year/engine.

Try adjusting the knob on the ECU. Count the number of "clicks" on the knob, or mark it so you can get it back to where it was if you need to. Going counter-clockwise should make the mixture leaner at idle only. If that helps your CO, then you were running rich. If that doesn't help, try going the other way.

--DD