NOx kicked my butt in emissions testing

[89IROC&RS]

Hey all, tried getting the IROC on the road after ignoring her for the past two years or so, she passed saftey inspection but failed emissions, but im a little ashamed to admit im pretty confused by the results and how to interpret them, so i thought id bounce them off you.

Background - car has been sitting for years, has old gas, a bottle of octain booster in the tank. the last time i was home i diagnosed a faulty injector so this morning i swapped in a set of accel 26lbs/hr injectors all around. In doing the tuning after the install, i found out my timing was WAY off, a product of just making it run before. so i set the base timing with the timing connector disconnected at 0*, with the connector on it seems to be running at about 7*-10* advanced. also with the connector plugged in, the idle speed is right around 750rpm. although i think my idle set screw isnt set right. (admittedly its because i messed with it before). all that being said, the car seems to be running better than it ever has before.

one other note, that could be quite telling, the wire connected to the EGR valve under the plenum broke off at the valve, i tried a quick solder repair but it was not pretty.

All that being said, my results were as follows...
15 mph
HC - Limit 48 - reading 47 - pass (barely)
CO% - limit 0.19 - reading 0.04 - pass
NOx - Limit 632 - reading 1400 - FAIL

25 mph
HC - Limit 88 - reading 62 - pass
CO% - limit 0.28 - reading 0.07 - pass
NOx - limit 614 - reading 1098 - FAIL

OH and the car also has a 2600 rpm stall converter

as of right now, im thinking the EGR is the culprit because of the broken wire and half assed repair job, but i didnt think it would cause NOx THAT high.

the other possibility is the catalytic converter, but the really low CO reading kinda dosnt fit.

something else ive read....but kinda confuses me, is that a lean condition can cause high NOx and HC with low CO, but with slightly larger injectors on the car now, i dont think thats the culprit.

any thoughts?????

[GreyGoose006]

is the compression ratio stock?
higher compression leads to high nox.
also its possible that the bad gas was the culprit.
if it were ME, id get the timing right, get the AF mix right, and put new high test gas in it. then get it fully warmed up and try again.

if you have different heads, pistons or whatever, anything that changes the compression, than you need to sort that out first.

octane booster does almost nothing to boost the octane. theres a thread around somewhere, maybe in engineering tech... read it.

[chevyrulespops]

It could be a combination of a bad catalytic converter and a malfunctioning egr valve...Since u did mess with the egr, I would try fixing that first and hopefully that will do the trick.....Rhodium was used in the converters to lower NOx and it might be depleted by now...good luck

[poormillionaire2]

I am going to say the main problem is the EGR. Since its main purpose it to lower NOx released in the combustion chamber, and you're spitting out numbers that read like you deleted it, then I would start there.

[Morley]

Your base timing should be 6* BTDC with the ESC wire disconnected.
After all of that time I would drain all of the old gas and put in fresh gas, possibly with some seafoam in it. I'd also pull the EGR valve and look at it's passages on the under side. Spray them with Valvoline Synpower carb/ TB cleaner and get them cleaned out. Then fix that wire. Mine broke off years ago too and I managed to solider it back on. If you just can't get it on good you can replace that little thing it hooks to, it is called an EGR diagnostic switch and won't cost much. It just screws into the EGR body.

[chevyrulespops]

Did u get it to pass???