I have 235k and worn piston rings, burn about 1qt every 1000mi. Maybe a bit less than that.

Usually use this for out and about town, errands, 35mph to 55mph most often. Solid runner. And 45-50mpg still!

Passed emissions two years ago. Failed yesterday

Says high HC (overlimit) and high NOx (just under limit). I get a free re-test this Friday, so looking for tips. Can I do anything simple to get it back in spec by then, or is this the end?

Since I burn oil, I figure the spark plugs are fairly well fouled. I plan to change them, at least. Also because the NOx was high, wondering if a weak spark is causing that..

Spark plugs were last changed about 2 years/7500mi ago. Nothing special, just the copper ones.

Or is it more likely my cat is poisoned and I won't be able to pass w/o replacing that?

 

California?

Long story short, my NOx problem was due to poor injectors.
A new cat will definitely help but I would fix the piston rings and everything else before doing that. Or you'll end up destroying that CAT as well.

 

ignition timing too advanced, fuel pressure too low, clogged fuel injector are nox forming failures. and EGR if you are in cali or the car is cali emissions. chase the nox and the HC will fall in line. also try to clean the combustion chambers with seafoam before your next text - do the overnight piston soak.

 

Someone had blocked off my EGR with a plate. That is why i failed NOX here in Ca.

 

That pathetic moment you have to get emissions tests on a 80's model car,

Ca, citizens need to go on strike for that bullshit.

 

Well, I changed my spark plugs last night, and the good news is I passed today.

In case anyone's interested, my numbers (1st test, 2nd test):

HC GPM: 2.57, 1.98 (Limit 2.00)
CO GPM: 15.78, 10.27 (Limit 20)
CO2 GPM: 263.99, 226.51 (No limit)
NOx GPM: 3.97, 3.36 (Limit 4.00)

My interpretation though is that since all the numbers across the board are lower, the tech was probably goosing the gas pedal the first time, or can't drive a manual. Otherwise, more complete combustion should show HC going down, but CO2 going up..the carbon has to go somewhere..

Anyway, something I'll probably need to keep an eye on as I passed HC with 0.02 to spare.

 

Next time empty your tank and run meth hydrate. Worked for me on more than one occasion.