Emission Inspection Results Fail Question

[Bornindesert]

The truck is an 88' 4 Cyl manual 4 Spd with 145,000. Also a 4X4 :thumbsup: Also a red Sport Truck...

 

Original Arizona truck from Payson where there is no inspection or emmisions requirement. In Phoenix, we have the dreaded inspection and emmisions test just to Title the truck.

 

So, 1st attempt:

 

Equipment (Gas cap, Evap Sys) - Pass

Hydrocarbons was 4.36 - limit is 3.00 Fail

CO was 62.65 - limit is 25.00 Fail

NOX was 5.11 -limit is 4.50 Fail

 

Looked underneath - a test pipe was living where the Cat goes. No problem, had a good Cat and swapped it in last night. took it back to the Inspection station today. I know, should have looked underneath before 1st attempt...

 

2nd attempt:

 

HC was 2.18 - Pass

CO was 27.03 - Fail (but just barely !!!)

NOX was 3.34 - Pass

 

Plan of attack (and to be modified based on suggestions) is to change the oil and filter, remove/inspect/replace spark plugs and take it back through next week. I've read on another thread that the O2 sensor is a must replace, so I guess I could go there as well. The truck really runs pretty decent for 145,000, just need a few points of CO and life is good...

 

 

 

[Eagle]

The oxygen sensor usually addresses hydrocarbons. NOX is usually caused by a lean condition, IIRC. Carbon Monoxide -- I don't remember what causes that.

 

Do you have methanol-doped gasoline where you are? I'd suggest dumping a can or two of fuel system cleaner into your tank and driving it down to almost empty, then fill up, go to your favorite parts house, and on the shelves where they have all the chemicals buy yourself a can of one of those "Guaranteed to pass emissions" snake oil products.

[moos]

I just went through this on my "New" 87 comanche. Had papers of how it passed months before but  smogs are only valid for 90days so went down to a shop. Find out my truck  EXCEEDED GROSS POLLUTER limits. Which means I failed worse then ever.failer of fails and maxed out one of the readers.tore the motor down to the block cleaned and replaced seals, added thermostat, cleaned valves injectors,intake,TB. Haven't smogged it yet gotta tackle couple More stuff.

[Oyaji]

The oxygen sensor usually addresses hydrocarbons. NOX is usually caused by a lean condition, IIRC. Carbon Monoxide -- I don't remember what causes that.

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I'm kinda rusty on this - a few years ago I could have answered authoritatively as it was a particular area of expertise for me... but here goes.

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Eagle is right about NOX coming from a lean-burn run condition. That puts that reading at odds with HC and CO being high, as they come from rich-burn run condition. O2 sensor should help with all 3 pollutants, and EGR will help with NOX (by reducing peak combustion temperature).

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I would bet on a well-tuned 4.0 in good condition to beat emissions limits of that era even without a catalytic converter installed. Two things come to mind that might help you. First is to question the test: is the test actually using the emissions limits in effect at the date of manufacture, and is the calibration of the test equipment up to date? It just doesn't seem right that the test values you reported are correct. Second, if that doesn't get you to pass, then after making sure you have the engine running as perfectly as you can get it (making sure all your sensors and their connections  [including grounds] are good, particularly the O2 sensor - checking your cap, rotor, and spark plugs and wires wouldn't hurt either), consider adding an adjustable fuel pressure regulator for tweaks to beat the test.

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One last thought - maybe you just need to try a different test facility.

[ParadiseMJ]

 "Guaranteed to pass emissions" snake oil products.

 Normally, I'd say just that..."snake oil".  But in this case since you came so close to passing CO and passed everything else with room to spare, I'd do it.  CO is indicative of unburned fuel.  Check your plugs, drive it in hot.

[Bornindesert]

Thanks for the ideas - I'll update once I get it ready to roll through...again.

[carnuck]

I passed the sniff test here with no cat (casing was there but nothing inside) with my '86 2.5 5 speed. EGR not functioning causes high NOx (they are caused by excessive combustion temps and/or timing too far advanced, which also causes ping) Slightly too high CO can be caused by misfire, etc (plugs, intake loose) OR thermostat too low.