That time of year again.. time to try to get the old Iroc to pass the sniffer.

This year, i moved from NJ to PA, and now the tests cost me money. I failed the first try.

GAS--- Limit----Test Value
CO-----1.10---- 0.22------- PASS
HC------275-----410-------- Fail
NO-----3600-----9057------Fail

I got some ALDL data from the car, and the only thing that looked like it was out of the ordinary was that the BLM was 150 at idle.

What confuses me is, if the BLM > 138, the car is suppose to be running lean, but the HC's are high, and Hydro Carbons are just unburnt gas, which means its really Rich... Right?

Anyhow.. any clues on where i'm suppose to start? I was looking over the shop book, and it said to look at the AIR system, something about seeing if the BLM's drop when you pinch the air hose leading to the driver side, but i didn't get any drop or anything.

Last year, it took me 3 tries to get past the NJ test, and it was pretty much the same thing then... High HC's and NO. Changed all the EGR stuff and did a top end cleaning. I think eventually they just passed me cause i had all the reciepts for a waiver. I'd really like to just get things down so that i don't have to worry so much about this every year.

 

A common misconception is to confuse "before correction" fuel data with "after correction" fuel data.

BLMs are a correction factor that the ECM uses to maintain a certain air-to-fuel ratio (AFR). If you're seeing a BLM reading of 128 (the median value), that means that the ECM doesn't have to incorporate any correction to the preset fuel curve to arrive at the designated AFR.

Anything above 128 means that the oxygen sensor is detecting a lean condition and the ECM is adding fuel to reach the AFR; less than 128 and the ECM is removing fuel to compensate for a rich condition. A vehicle that has a BLM of 128 should (theoretically...) be at the exact same mixture as one with a BLM of 110 or 150 -- the only diference being that the ECM is applying a correction to achieve the specified AFR (in other words, the preset fuel curve isn't completely accurate in terms of the AFR).

Now, this logic may change if you're at either of the BLM extremes, 108 or 160. The ECM can only add or remove so much fuel, so you might actually encounter a rich or lean condition (offset from the AFR, keep in mind) depending on how inaccurate the preset fuel curve is.
Assuming that the AIR injection equipment is working (and it's being directed to the manifold), it would make sense to see a drop in BLM -- you're removing oxygen that the ECM is accounting for (it knows that AIR is enabled), so there's an abundance of fuel... which will be removed to maintain the AFR.

Not sure about helping you out with the PA tests -- but they can be a pain. My Camaro's been emissions-exempt for a few years, but I usually say a little prayer right before the Jeep goes in. It seems to work...

 

looking at what you posted, all 3 are telling me your lean.

high NOx can becaused by,
problems with the EGR system, a weak or bad cat, running too lean, ignition timing too high, bad gas.
the motor running hotter than what it should can also raise NOx, but normaly not by alot & not any where near what your doing unless its so hot its causing it to ping.

high HC can be either rich or lean. too rich & it isn't able to burn all the fuel, too lean & you get into lean misfire.
other things that can cause high HC,
timing too high or too low, a plain old miss from plugs, wires, cap & rotor, a vacuum leak, bad valves or rings can also cause high HC.

a CO reading of .22 is low, your CO needs to be a little higher, around .50 or so unless the cat is really working its butt off.

some of the things you'll want to check are,
your complete ignition system, make sure your O2 sensor is good, an 89 has a MAF doesn't it? if so the check the MAF sensor & the boot between it & the motor, check for any vacuum leaks, your fuel pressure, both of the the temp sensor reading, & maybe do an injector flush.

a pre-cat reading of the gases would let you know if the cat was doing its job or not, but that can only be done by a shop with a 5 gas.

if they listed it, what was the O2 reading?

 

Thanks for the info. They didn't give me a reading on O2.. the only other thing i see on the paper is Dilution Reading of 13.1%.

The only things i've really done lately was a valve seal job, and i orginally thought that maybe there was some carbon build up from the oil leaking into the cylinders, and i tried to address that by running a bit of Seafoam through the break booster line. Made an interesting amount of smoke... car 'seems' to run better.

When i did the seal job, i changed the spark plugs and inspected the wires.. but i guess i should do a whole tune up just to be sure. I changed all the EGR stuff and the O2 sensor last year, but maybe i'll just look into some AC replacement parts and see what happens when i change them again.

The Fuel Injectors arn't too old... i just put them in about 2 years ago. The fuel pressure is right on, i do have the adjustable fuel pressure reg in there though.. guess i could goose it up a bit if i really am running lean. I try to run only 92octane gas... its a bitch with gas prices what they are right now. Timing seems to be dead on mechanically. I think i need to get a temperature probe to see if the computer is getting the right temp. Car does have maf... i'll see if it runs better disconnected.

Wasn't there something about dropping the timing back a bit to lower the NOx?

I dont' think the CAT is as old as the car... seems to be a CATCO replacement.. but maybe i'll have to look into a new replacement.

Sadly enough.. this wasn't so bad in NJ. I could go to the inspection station as many times as i wanted untill it passed. Here i get one free retry and then if it fails i have to pay agian. If i don't pass on the second try.. i think i'm gonna go to a 'freindly' mechanic and get me another year of leeway.