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Hi Bob,
Thanks for the excellent link.
It remains a mystery.
Incomplete combustion due to fouled spark plugs.
High HC
* Improper timing or dwell
Isn't this set by the computer. I thought you could not set timing on 940's?
* Damaged ignition wires
Put in new wires. Still lean.
* Poor compression
Have not checked yet.
* Vacuum leak
Not that I can find.
* Ineffective or faulty air management system (ECM control of air/fuel ratios)
ECM=Computer? I have not heard of many computer failures on this car. Maybe I should see if I can find a known good one for swap?
High NOx
* Malfunctioning EGR valve
No EGR on this car
* Lean fuel mixture (AFR above 14.7, Lambda above 1.0)
Well, I know it's lean. Can't figure out why.
* Improper spark advance
Isn't this related to timing above?
* Thermostatic air heater stuck in the heated air position
No hot air intake on this car.
* Missing or damaged cold air duct
What's a cold air duct? Checked the air-filter and housing...all good.
* Combustion chamber deposits
Recently ran Techron so this should not be a problem.
* Malfunctioning catalytic converter
Cat is new.
Also replaced spark plugs and distributor cap -n- rotor since I had them laying around.
No change.
Swapped in known good Knock sensor.
No change.
That leaves -
1. Compression
2. ECM
3. Fuel pressure?
Funny thing is that the car runs great. No obvious symptoms of lean running.
When I pulled the (Volvo) spark plugs there was obvious blistering of the ceramic part.
???
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