sillbeer

I went through emissions for the second time. My readings from the first test where as follows:

HC 1.81 Fail
CO 12.79 Pass
NOx 3.11 Fail

I knew the car needed a new headgasket so I figured I would have that fixed along with some other basic things. I had the head rebuilt, new hg, new front engine seals, belts, spark plugs, plug wires, cap, rotor, and O2 sensor. I just got back from emissions and it is even worse now.

HC 2.26 Fail
CO 12.15 Pass
NOx 3.44 Fail

The only modifications to the car are Porsche Cup software and manual boost controller set at it's lowest setting which is .8bar. If anyone has a set of stock chips I would be interested in picking them up. I want to try and pass legally if possible but without dumping a ton more money into it.

-Destin

reno808

maybe ur cat or ur o2 sensor is bad

Tony951

I failed emissions with my 88 951 (CO only) - I replaced the O2 sensor and passed. My O2 sensor appeared to be almost completely plugged up. This would be a cheap start...

Porsche-O-Phile

I just did a seafoam treatment on my 944 and then put a new O2 sensor on it. Holy cripes, what a difference! I have not yet burned through a full tank of gas to see what kind of mileage increases I've gotten, but more to the point this was done in preparation for smog check - I'm virtually certain it'll pass with flying colors now barring any problem with the cat coverter.

O2 sensor makes a HUGE difference.

KuHL 951

Xylene is your best friend come smog time here in Cal.

ibkevin

Ever since the new server, I'm not sure how to link an entire post but this is waht I did.

Ran the car at 75-80 for about 20 min, pulled into the test only center about a mile from the highway and left her running. I was the only car there so she went right on the dyno. I did provide a little distraction when he lingered too long with his inspection mirror in the area of the Tial.

Driven only 10k miles in two years! It doesn't help my points per mile ratio *shrug*.

I did add a bottle of CPC "Guaranteed To Pass" additive to the 10gals in the tank.

After running the APE II vice the MAF, I really notice where the Tial/EBC lend they're muscle to the car. The Tial/EBC keep the turbo spun up till boost limiting kicks in, but the MAF provides useable gains in the 4k + range where the APE II is pretty much DOA.

15mph/2363rpm/CO2-15.1/O2-.1/HC-48(116max)/CO-.37(.74max)/NO-413(791max)
25mph/2404rpm/CO2-15/O2-.0/HC-62(91max)/CO-.51(.62max)/NO-433(730max)

sillbeer

I figured a new O2 sensor would have fixed it seeing as it was running rich but obviously not unless I got a bad one. I might just have to put in a gallon of denatured alcohol and call it a day. My rx7 passed with flying colors with that stuff.

-Destin

PEvans

If you are running your original cat you are probably going to have to replace it eventually, even if you find some tricks that work this time. The high NOx reads are the result of the cat. A new cat shouild have no trouble. There are aftermarket cats for the 951 that work fine and are not that expensive. And emissions troubles become a thing of the past if your car is in good repair.

moronputz

High HC and NOx indicate rich running and most likely a damaged cat. Chances are the chip is your rich running which may well have advanced the cat ageing. Even putting a standard chip in is not likely to help your NOx enough to get through the test.

Run your tank low and put some alcohol in it just before you go for the test (try to go no more than about 20-25% and keep your mileage and boost pressure as low as possible. Also, be mindful of high throttle as a rich alcohol fuel mix may give you some problems. Straight after the test fill up with whatever fuel you normally use. You should sail through the emissions tests.

ztnedman1

Do what i did. I worked at our emissions place for 2 yrs got in close with everyone and now i wont have to worry about it ever again. If they are supposed to fail they bypass it and pass it

IanS

Did they give you any other numbers, like O2 %?

Having HC and NOx high may indicate misfires, but you've replaced most of the ignition system. It might be worth trying a new ignition coil, especially if you can borrow one.

Going back to stock chips is a wise choice anyway, but there is probably another issue here. Have you checked the car for intake and exhaust leaks?

sillbeer

The co is 446.70. What doesn that mean? The car doesn't have any exhaust leaks and i'm fairly certain it doesn't have any vacuum leaks. It does hesitate ever so slightly when on the throttle. I'm guessing this is because it's running rich with the cup chips. Is there any way to bench check the coil? Thanks.

-Destin

IanS

Clark's garage has a resistance check you can do on the coil. 0.4 to 0.6 ohms on the primary and 5000 to 7200 on the secondary. I admit its a bit of a long shot, but probably worth checking.

five-o

Glad we don't have emissions checks in Michigan

Good luck though. I'm sure it's frustrating.

Jeremy Himsel

If you want, stop by my house tomorrow and I'll go through it. I have a drawer full of chips and will get it figured out for you. Shop opens @ 9:30.