Tom_DB1

Classic 951 Smog failure, HC and CO are OK at both speed but NO fails at both speeds. CAT had 135000 and O2 had 50000
Replaced CAT, O2 sensor. Checked all hoses (propane test) no vacum leaks
Injectors test good, Ran car hard before test, left running while waiting for test. O2 signal transitions between .92 volts and .15 volts as it should.

retest, no change
15 MPH
CO2 14.4, O2 .7
MAX HC 116 mine 97
MAX CO .74 mine .42
MAX NO 791 mine 1330

25 MPH
CO2 15.1 O2 .2
MAX HC 91 mine 26
MAX CO .62 mine .01
MAX NO 730 mine 741

My question:
I'm using welt chips which I nor the makers have any idea what the 8 position switch settings are so I'm going back to stock chips so I can retard timing a little just for the test. Can I just switch the DME back to stock or do I have to do the KLR also?



1987 951

400hp944

I had the same exact issue you are having, only I was running my stock chips. NO was high at both speeds.
Put 5 gal of 109 octane unleaded in it, run it for 30 miles or so, it'll pass no sweat. Worked great for me.

zoltan944

Is your EGR functioning properly?
Either way you should test with stock chips so we can see what it does stock

project951

do 944s have egr valves ?

zoltan944

actually not sure. LOL
thats the normal issue for NO tho. I know the 928 had air injection in the cat. I need to read up more on the 944

Spidey944

um... no EGR on our cars.... wanna take another stab?

Spidey944

Just like the last person who posted high NOx levels, this is being caused by high combustion temps (2500+ deg F) The trick mentioned above about raising the octane level may help, but also start with a good clean air filter, and set of fresh plugs. Do you have a wideband? A lean mixture will cause high NOx all day long.

quinnfiske

In my car, the cap on the AFM idle mixture adjustment was missing which meant someone had adjusted it. I richened it up and it finally passed. It had a big impact on emissions. This graph was helpful:

http://www.systemsc.com/graphs.htm

400hp944

The race fuel burns cooler and will lower the NO. Been there...done that. The stock cat on these cars is rather large, so if you need a new one, get the biggest one you can get. I had the shop put in one for a Jeep Cherokee (non EGR). New flanges, and a test pipe welded into my Lindsey 3". Worked great. Swapped out the cat when I was done. Took about 10 minutes.
Not real sure about the chips. I used the stage II Autothority and it passed fine.

Tom_DB1

Put OEM chips back in, Retarding timing 2.7 degrees.

Went to smog, FAILED. The indications were so bad that he stoped the test and didn't charge me so I don't have the numbers. He said I need to go to a Gold Shied Test facility.

And the story will continue


Tom
1987 951 Now a Stock engine, updated suspension, brakes and tires

quinnfiske

In the course of getting mine to pass, I replaced the O2 sensor and the DME temp sensor. The temp sensor makes the mixture richer during warm up and they can drift with age/miles. It is only about $20 and is at the front of the cylinder head on the intake side. And I would have someone check/adjust CO level like I mentioned earlier.

I passed with the original cat with 178K miles. I also ran a bottle of Guaranteed to Pass stuff though the car, but it still failed afterwards, don't know if it helped or not.

Tom_DB1

I've heard a lot of posters say that daignostic smog checks are not sent to the state of CA but they are. Use this web site to check you cars record. It has all my dianostic runs along with the official ones too.

smogcheck.ca.gov.vehtests/pubtstqry.aspx

With my cars failure record they will not test it again at a smogtest only facility. I recieved notice today that I must take my car to a CA. Gold Sheild facility to perform smog repairs and testing or remove the car from the road. The upside is that the state gave me $500 of repair assistance voucher. I pay the first $100 and the next 500 is on them then I pay whats over the 600 total.

The saga continues.


Tom

951 Now stock engine, Yellows, 968 030, updated brakes and clutch

Keithr726

Sounds like a boat load of CA BS to me!

PEvans

I would suggest putting in a new cat if it is original or old. IMO it's really hard to make CA smog numbers with tweaks that are sufficient in some other states -- here the cat has to be working.

Fair warning, though, I'm where you are with a pretty new replacement (aftermarket) cat still under warranty (that is, it worked great for the first couple of years and now nothing). I tried a new 02 sensor and haven't yet done the retest, and now you have me worried about multiple fails.

ibkevin

I have a pending test-only myself.

Talking with BAR, gross polluter only lasts one renewal cycle, as long as the car is sat on the next test. Rumors of not being able to sell a gross polluter are BS.

I swap the stock DME with the Vitesse II chipped DME for the test and reinstall the stock air box. This year I'll spray the too pretty Tial with black BBQ paint and have yet to configure a Jboot for the new 3" turbo inlet. Leave the KLR alone.

A local lister that used to conduct smog testing siad to run regular octane because higher octane increases ignition temps which results in higher NOX.