If you were in Socal, I could get you passed for around $200.

actually, the prices on that web page are VERY reasonable. that is exactly what i'd do.

Also, the cat does nothing in regards to NOX emissions.

not true, exactly. if you look through my posts, you will find that i had a similar problem, found my cat was gutted, put a different one on there, and passed. if the cat is gutted, there is less back pressure, less backpressure can actually cause the car to run too lean. the car running too lean can cause the high NOx, which is exactly what i found when i did the last and passing emissions test.

Yes, but, his other emissions are in line showing his cat has yet to be disembowelled.

Hopefully you get to read this before spending to much money on a lot of high $$$ repairs. The Evil Empire otherwise known as the Republic of Cali has spread it's auto laws like the clap upon the rest of the country. Yes, even here in the desolate wasteland known as Albucrappy, NM we have adopted Cali's emissions laws. Anyway, I had the same emissions problems with my 86 944NA. Figured I do a little trial and error with parts replacement instead of trying my luck with a $100+ an hour shop rate with some mechanic that can only figure something out if he can plug a lap top into the car. Can't seem to find the emissions slip so I can't give you exact numbers just the knowing nod of a similiar fate. Before my first emissions run I gave the 944 a complete tune-up and coil upgrade. Car ran great-failed the test. Figured the O2 sensor was bad. Replaced it-failed the test. Thought the cat maybe bad but figured that the cat doesn't affect some of the contaminents so that couldn't be it. Replaced the fuel regulator and fuel dampener. Then started looking for vacum leaks. Found some tech stuff saying Porsche is very sensitive to vacum. Found a cracked hose running from the top of the motor to the MAF sensor and blam-passed with flying colors. Emissions numbers were spec on. So, before you spend upwards of $500 trying to run down this problem look for a bad hose that'll cost you less then a buck.

Good Luck!!

Thanks, I've checked and haven't found any leaks. I went ahead and ordered the CAT. It cost $120, so not too expensive.

I'll bite the bullet on this one as I've done shocks, tires, rear brakes, alignment, plugs, stereo, etc, and just want to get Ca plates on it and go! Besides the alignment and tires I haven't paid a dime to a shop yet, guess I'm due(oil leaks need fixing too...)




Also, I disagree with the idea that a new cat will not have much of an effect on NOX emmisions. The 924S uses a 3-way cat, one of the scrubbers is meant to lower NOX numbers, so this should solve my problems. The cat on the car appears to be original.

New plugs, 91 octane, and messing with the FQS did get me damn close, so hopefully that will help a future searcher who's numbers are a bit closer to passing.

The cat will definitely have an effect on emissions. That's the purpose of it. It just doesn't affect all of the pollutant values. And of course modern cats are way more effective then 20 year old stuff. Check out this website. It's not overly helpful but it gets you started in tracking down emissions failures. I'll take a look, I think I have a lot of emissions related stuff floating around in addition to this.

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

"Emissions Tests

Emissions failures result from excessive levels of CO (carbon monoxide), HC (hydrocarbons), or,
NOx (oxides of nitrogen). Some emission regulatory facilities just require static tests (an unloaded
engine) and others require a dynamic emissions test (a loaded engine via a basic dyno). Late model
vehicles ('96 and later - OBDII) require an additional initial test check of the OBDII readiness
states. A failure of the readiness states being complete results in the emissions test being aborted.
The readiness states consist of non-continuous (at startup) and continuous (while driving) tests.
Completion of the tests may require additional driving of the vehicle or a mechanical correction to
the emissions system on the engine. Some non-continuous readiness states can be run using vehicle
specific scanners.

A high CO level can result from a bad fuel pressure regulator, a bad air flow meter or air mass sensor,
a bad performance chip, a bad temperature sensor, or a bad O2 (oxygen) sensor. A HC level failure
can result from a bad fuel injector, a weak cylinder, bad spark plugs or ignition wires, an intake air
leak or a bad O2 sensor. A NOx level failure can result from a too advanced ignition timing, a lean
fuel mixture, a bad performance chip, or a weak catalytic converter. The typical values for each are;
CO < 1%, HC < 100 ppm, and NOx < 500 ppm. The level of CO2 (carbon dioxide) which results
from the catalytic converter reaction is a measure of the effectiveness of the catalytic converter.
Typical values of CO2 are 13 to 15 percent.

Lastly, a bad fuel injection unit or ignition control unit may be the cause of any emissions test failure.
The above mentioned possibilities, though, should always be checked before assuming bad control
units or performing other costly repairs."

put a dose of ethanol in your tank, drive the snot out of it, to get the cat good and hot. it works best, when its stinking hot, and then get it tested, while its still "on the boil". the ethanol will make it run like crap, but your emissions will be extremely low.

Yea, the cat has to be good and hot. Especially if it's an older unit. And, depending on your location your gas already has an ethanol mix...or something similiar. Here in the mountains of New Mexico they sell a gas mix. This pelican site, http://www.pelicanparts.com/911/technical_specs/911_DME_troubleshoot.htm can be a little bit of help as well. Not specifically for a 944 and not overly detailed it too is a good starting/reference point. Keep your posts up if you can. I'm curious to see what the problem boils down to.

Just went to smog with the -NEW- cat(aftermarket in the link above)

****ING FAILED!

I am pist. Nearly all my levels -INCREASED-

-------02 -- HC -- CO -- NO
15mph 0.6 27 0.01 1478(fail)
25mph 0.4 17 0.01 1143(fail)

oh man. what kind of troubleshooting have you done on your fuel pressure?

I'm not sure. It was listed as a direct-fit replacement for my car. I am in the middle of trying to contact someone at the convertor company to find out.

Unfortunately I can see no other reason for the numbers to increase.

Talked to the cat guy. It is a 3 way cat, should not have had the problem, should not have had the increase, going to get back to me...

i am starting to think you have an injector/fuel pressure issue.

None. The car is stock. I've had the DME apart and no chip, stock exhaust, air box, manifold, etc.

I've replaced the air cleaner, plugs, fuel filter, etc. All maitenance is up to date.

One curious thing though. The exhaust shop who installed the cat yesterday said that there was a -second- bung in the header, that looked to be threaded and was empty(no plug or sensor) is this normal?

Thanks.

I just went back through this thread, and it is obvious (at least to me) that you totally ignored the information I gave you, so I'll try ONE MORE TIME:

YOUR ENGINE IS RUNNING LEAN. Check the spark plugs. The normal color is Tan to Brown. Yellow to White is Lean, Dark Brown to Black is Rich.

Verify that the FQS in the DME is at the STOCK setting (Fully CCW as I recall, but verify that on F.R. Wilk's site).

Verify there are No, ZERO, ZILCH, NADA, vacuum leaks. This includes injector to intake manifold seals and intake manifold to head gaskets. Make sure the intake manifold bolts are properly torqued.

Visually inspect (this means you have to look) ALL vacuum lines, hoses, and the intake J-Boot for signs of cracking, tears, holes, etc. After said visual inspection, verify that ALL hose clamps are tight. If you can twist or move the hose at the fitting, the clamp needs to be replaced. The OEM clamps stretch over time and loose their grip. Use small nylon cable ties (tie wraps) to keep the hard plastic vacuum line and rubber "adapter" connections tight.

Use a vacuum gage to check manifold vacuum. You should have between 15" and 20" of Hg vacuum at idle, and the needle should be steady. A pulsing or jumping needle is indicitative of either broken valve spring(s), burned valves, damaged valves, or damaged valve seats.

Use a DVM (Digital Volt Meter) to verify the O2 sensor's output. With the engine at normal temperatrue and at idle, disconnect the sensor and read the output. You should see between 0.60 and 0.80 volts DC.

If the O2 sensor does not read within this range, use a 6mm Allen wrench to adjust the by-pass on the Air Flow meter. If the reading is too high, turn the by-pass counter clockwise to open the by-pass. If the reading is too low, turn the by-pass clockwise to close the by-pass. Do this in 1/4 turn steps, pausing between steps to let the O2 sensor reading settle out.

When you have a steady reading between 0.60 and 0.80 volts DC, reconnect the sensor to the DME and backprobe the O2 sensor. You should see the reading vary across 0.50 volts DC.

i think this open bung may be part of your problem. also, what cliff says, above.

I realize that the engine is running lean. That is why I cut timing as recommended, this did improve my numbers significantly. I also replaced the plugs wich were very worn. The new plugs have not been driven on enough to have any color indication yet.

I have checked for vacum leaks, but will do so again, very thoroughly.

I have not checked the 02 sensor output. I am planning to.

Your suggestion are helpful and I will try those procedure over the next couple of days.

That said, why would my numbers -increase- after replacing the original 17yr old cat with a brand new one? Even if I have not yet solved the root of the problem(lean condition) why would my NOX numbers jump by 400/600ppm???

Any clue on the 2nd header bung?

Replacing the original CAT may have increased the exhaust folw rate (which also lowered the back pressure), thereby exassarbating the NoX problem.

The second "bung" may be the fitting for testing emissions upstream of the CAT. Normally there is a stainless steel line connected to this fitting. From there the line goes up into the engine bay.

While we are on the subject, you may want to examine the Air Flow Meter for any signs of "tampering". Look closely at the seal for the black plastic cover. If the cover has been taken off, chances are someone "tweaked" the vane spring pressure.