5.2L V8 4x4 '94 Gen 1 with 175k miles on Odo
last smog test 12k miles ago - 2 years prior
Everything passed with good margins
NOx was 250 / 491 ppm max
HC and CO - very low.
Prior to getting the passing scores I replaced the EGR valve, CAT, ignition parts, TP sensor, O2 sensor, thermostat, Coolant sensor and coolant. All of the parts were replace within 5,000 miles of that test.
This time I only replace ignition parts and oil & filter
NOx results measured was ~ 900 / 491 ppm - thus failed the smog test.
I get to go back in 60 days for a free retest.
In the interim I found out the gasket under the air filter hsg. was cracked and I replaced it, also the hose from the PCV to vac port got replaced and the gastank cap that had cracks in the seal.
Then I found it had mis-wiring in the ignition wires at the cap.
#3 and #6 were reversed on one side and
#5 and #6 reversed on the other bank.
(firing order 1-8-4-3-6-5-7-2)
Fault codes are: 12 and 27
I believe 27 is an intermittant possibly in the Fuel Injection harness but have no idea how to repair it.
Can any of the above cause the high NOx?
Could permanet damage occur to the CAT due to the mis-wiring?
Any comments/help appreciated.
ron
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