Duck05

Wife took our stock engine SC300 for the bi-annual smog check and it barely passed one of the categories by "1 point"; tech told her it likely will not pass the next time.

Only change is the rear exhaust (replaced stock mufflers with Magnaflows) but it is a '92. Tech also told the wife that the state changed the ranges of some of the emission levels making it more difficult for pre-96 cars to pass.

Anyone else run into this and what repairs/enhancements/changes did it take to pass???

Guess we have 2 more years before the next go around but this is discouraging to invest in these cars only to get run off the road by the state....

PuReChaos

It would help to know what all your measured numbers were.

lbintab

iTrader: (1)

Probably need to do a tune up and change your cat in order to pass again

Duck05

Yes.... Sorry... The "HC PPM" measured at 74 with a Max allowed of 75. The CO came in at .07 and the NO was 401 (Max 533) (these are the "15MPH" figures).

First time I have really looked at a smog check document in a long time for any of my vehicles so not sure how to put these into any context. Last I heard, changing out the catalytic convertors on our cars is a pricey endeavor (at least for a '92) but if that's what it takes next time than so be it....

metaleckz

iTrader: (9)

Its 200 to change the cat

PuReChaos

Mind posting the 25mph figures for those as well? As well what the O2 and CO2 measurements were. That could help identify if the cat is going bad. I mean from what you've listed it sounds like some things to try before replacing the cat would just be as lbintab said, a tune up. Like spark plugs would be a good place to start if they haven't been changed in a while, possibly ignition timing... those could help your hydrocarbons..

Your CO indicates your car is running slightly rich. Cheapest part there would probably be pcv valve and if you want to go further, inspect that your fuel pressure is within spec. too high of fuel pump pressure or a defective pressure regulator can cause higher CO.

Your nox isn't bad (from the 15mph reading). Not sure if your sc300 has an egr or not, but if so, maybe the passages are beginning to get clogged, carbon build up on cylinders can cause this sometimes...

I'll try and help a bit more once you post up data, but probably just start with a tune up.

Duck05

Okay. The plugs, wires, and rotor were changed less than 2 months ago. The full measures read as:

%CO2 %O HC (PPM) CO (%) NO (PPM)
Test RPM Meas Meas Max Ave Meas Max Ave Meas Max Ave Meas

15 MPH 1620 14.5 .02 75 31 74 0.49 0.04 .07 533 184 401

25 MPH 1837 14.4 .02 57 22 42 0.57 0.03 .06 491 141 339

(sorry that the formatting is not being retained.... hopefully the above makes sense)

Any additional pointers or advice is appreciated... I have 23 more months to worry about it but never too late to prepare.... Thanks....

PuReChaos

Obviously if they're two months old I wouldn't change them. HC is affected by a few things.. typically most components of the ignition system (spark plugs, wires, coils, ignition timing) or oil consumption can cause HC to rise, do you notice any oil loss between changing oil? If yes, maybe weak piston rings or worn valve guides.

Not sure what I was thinking last night but your CO is fine. I guess I thought you meant .7 not .07.

Nox is a little high compared to average but not bad.

Your O2 and CO2 are really good. They are proving your engine to be really well cared for. Again comparing your O2 (.02) to CO (.07) your running ever so slightly rich. They definitely did change the ranges because your engine appears from the numbers to be running fine.

In 2 years when your up for another smog, you could just do a tune up right before. Change the spark plugs and make sure the ignition timing is perfect. But as you said you've got a long time to worry.

Duck05

Really appreciate the advice.... The engine is at 195K so the other elements you mention would not be too surprising.... Had to fix a lot of oil leaks and since then the oil levels remain steady...

Thanks...

VIP161

iTrader: (3)

Before you do anything, replace all your O2 sensors with Denso. That will significantly drop some numbers. Start with the cheap stuff. Spark plugs, wires, etc.