951 Failed Emission Test
07-20-2002, 12:34 PM
#17
Race Car
[quote]Originally posted by amaf:
<strong>Do what I usually do, slip the guy a $100, and you just passed the inspection w/o going through all the tests. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> </strong><hr></blockquote>
Here it's worth it, we have no repair cost limit. They don't care if you spent $10 or $10,000, if it doesn't pass, you don't get the sticker, 30 days later you are a target for a "uninspected" or "failure to make repairs" ticket.
<strong>Do what I usually do, slip the guy a $100, and you just passed the inspection w/o going through all the tests. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> </strong><hr></blockquote>
Here it's worth it, we have no repair cost limit. They don't care if you spent $10 or $10,000, if it doesn't pass, you don't get the sticker, 30 days later you are a target for a "uninspected" or "failure to make repairs" ticket.
07-21-2002, 02:11 AM
#18
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jpapanas,
I had the exact same problem with a '86 951 with 164,000 miles. High HC and NOx. Failed New Jersey emissions. I replaced the O2 sensor with the Bosch 15725 universal (it uses the original Porsche electrical connector with an easy to use splicer. $55 at Paragon). The replacement fixed the HC but the NOx remained high. Some suggestions were a bad cat, vacuum leak (too lean), engine running too hot. Car has new air filter and plugs. Still isn't fixed.
BTW the sensor is difficult to remove on a 951 due to lack of clearance. I unpluged the electrical connection and tied a piece if cord to it before pulling the wire down under the car. This makes it easy to get the new wire back up along the same route.
Then I put the electrical connector through the end of a 22 mm box end wrench (Craftsman) then slipped the wrench over the sensor in the exhaust. Bend the wrench a little to flatten it out a bit to give better clearence. The old sensor unscrewed with a little muscle. HTH.
If you pass emissions please post what needed to be fixed.
Steve '86 951
I had the exact same problem with a '86 951 with 164,000 miles. High HC and NOx. Failed New Jersey emissions. I replaced the O2 sensor with the Bosch 15725 universal (it uses the original Porsche electrical connector with an easy to use splicer. $55 at Paragon). The replacement fixed the HC but the NOx remained high. Some suggestions were a bad cat, vacuum leak (too lean), engine running too hot. Car has new air filter and plugs. Still isn't fixed.
BTW the sensor is difficult to remove on a 951 due to lack of clearance. I unpluged the electrical connection and tied a piece if cord to it before pulling the wire down under the car. This makes it easy to get the new wire back up along the same route.
Then I put the electrical connector through the end of a 22 mm box end wrench (Craftsman) then slipped the wrench over the sensor in the exhaust. Bend the wrench a little to flatten it out a bit to give better clearence. The old sensor unscrewed with a little muscle. HTH.
If you pass emissions please post what needed to be fixed.
Steve '86 951
07-21-2002, 04:02 AM
#19
Race Director
Yeah, both high HC & NOx may indicate something other than an O2-sensor. There's a graph somewhere that I can't find that plots HC, NOx & CO emissions at various AF-ratios. Typically, high HC leads to low NOx (cooler burn). And the inverse is low HC leads to high NOx (hotter burn). Somewhere in the middle, both HC & NOx are at medium levels. But you can't adjust the AF-ratio to place both HC & NOx at low because they occur at differnt AF-ratios. This is where the cat comes in...
07-21-2002, 07:52 AM
#20
Burning Brakes
[quote]Originally posted by amaf:
<strong>Do what I usually do, slip the guy a $100, and you just passed the inspection w/o going through all the tests. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> </strong><hr></blockquote>
In California, your results get electronically transmitted right to the DOT. You'd have to get someone with a clean car to take your place.
How long since the air filter element was changed? That has made a huge difference in my car in the past.
<strong>Do what I usually do, slip the guy a $100, and you just passed the inspection w/o going through all the tests. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> </strong><hr></blockquote>
In California, your results get electronically transmitted right to the DOT. You'd have to get someone with a clean car to take your place.
How long since the air filter element was changed? That has made a huge difference in my car in the past.
07-21-2002, 12:43 PM
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[quote] Originally posted by pig4bill:
How long since the air filter element was changed?...
<hr></blockquote>
I had switched to a clean K&N filter just before the test. I normally use a stock filter on the street and K&N for autocross/driver ed.
[quote] Originally posted by Danno:
There's a graph somewhere that I can't find that plots HC, NOx & CO emissions at various AF-ratios. Typically, high HC leads to low NOx (cooler burn). And the inverse is low HC leads to high NOx (hotter burn)
<hr></blockquote>
If you could find that graph it may be useful to others. So, I probably have more than one problem - one causing the high HC(maybe the O2 sensor?) and the other causing the high NOx(maybe the cat?).
[quote] Originally posted by SteveB:
BTW the sensor is difficult to remove on a 951 due to lack of clearance. I unpluged the electrical connection and tied a piece if cord to it before pulling the wire down under the car. This makes it easy to get the new wire back up along the same route.
<hr></blockquote>
Thanks for that advice Steve. Last time I had the O2 sensor replaced, they had charged me a OXY/ACET charge because they had to heat it up to get it out - I hope it's not that difficult this time!
I've made an appointment for a diagnosis this week. I'm hoping they find something that gets me a conditional pass without having any work done...
If I do pass the re-test, I'll keep you posted.
Regards,
Jim
How long since the air filter element was changed?...
<hr></blockquote>
I had switched to a clean K&N filter just before the test. I normally use a stock filter on the street and K&N for autocross/driver ed.
[quote] Originally posted by Danno:
There's a graph somewhere that I can't find that plots HC, NOx & CO emissions at various AF-ratios. Typically, high HC leads to low NOx (cooler burn). And the inverse is low HC leads to high NOx (hotter burn)
<hr></blockquote>
If you could find that graph it may be useful to others. So, I probably have more than one problem - one causing the high HC(maybe the O2 sensor?) and the other causing the high NOx(maybe the cat?).
[quote] Originally posted by SteveB:
BTW the sensor is difficult to remove on a 951 due to lack of clearance. I unpluged the electrical connection and tied a piece if cord to it before pulling the wire down under the car. This makes it easy to get the new wire back up along the same route.
<hr></blockquote>
Thanks for that advice Steve. Last time I had the O2 sensor replaced, they had charged me a OXY/ACET charge because they had to heat it up to get it out - I hope it's not that difficult this time!
I've made an appointment for a diagnosis this week. I'm hoping they find something that gets me a conditional pass without having any work done...
If I do pass the re-test, I'll keep you posted.
Regards,
Jim
07-21-2002, 12:52 PM
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[quote] Originally posted by *Rothmans*:
Drive your car until almost empty and put a gallon of methyl alcohol (aka gasline antifreeze) into the tank to cut your fuel.
It's cheating but your car will pass.
...
Ask any automotive store if they can get it for you. (the methyl alcohol)
...
So anyway, buy a gallon and mix it with a couple gallons of fuel. When your car is way too clean don't be surprised when they all stand around scratching their heads wondering why you're beating factory specs. (as long as your engine is tight and doesn't produce fumes you're okay)
And don't drink the stuff, you'll go blind
<hr></blockquote>
I found this while searching through the archives..
Has anyone else actually tried this? Wonder where I'm going to get a gallon of gasline antifreeze in the summer!
Drive your car until almost empty and put a gallon of methyl alcohol (aka gasline antifreeze) into the tank to cut your fuel.
It's cheating but your car will pass.
...
Ask any automotive store if they can get it for you. (the methyl alcohol)
...
So anyway, buy a gallon and mix it with a couple gallons of fuel. When your car is way too clean don't be surprised when they all stand around scratching their heads wondering why you're beating factory specs. (as long as your engine is tight and doesn't produce fumes you're okay)
And don't drink the stuff, you'll go blind
<hr></blockquote>
I found this while searching through the archives..
Has anyone else actually tried this? Wonder where I'm going to get a gallon of gasline antifreeze in the summer!
07-22-2002, 03:03 AM
#24
There's a graph somewhere that I can't find that plots HC, NOx & CO emissions at various AF-ratios.
<a href="http://boards.rennlist.com/upload/O2plot.jpg" target="_blank">Chart</a>
<a href="http://boards.rennlist.com/upload/O2plot.jpg" target="_blank">Chart</a>
07-24-2002, 05:21 PM
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[quote] Originally posted by jpapanas.
...I'm 58% over the limit on HC ppm, and 49% over the limit on NOx ppm....
ASM 2525 test:
HC ppm - Limit 127, Reading 201, Result FAIL.
CO % - Limit 0.71, Reading 0.64, Result PASS.
NO ppm - Limit 1415, Reading 2109, Result FAIL.
RPM - 1686, Result VALID
Dilution - 14.6, Result VALID
Curb Idle test:
HC ppm - Limit 300, Reading 154, Result PASS.
CO % - Limit 1.50, Reading 1.20, Result PASS.
NO ppm - Limit N/A, Reading N/A, Result N/A.
RPM - 1364, Result INVALID
Dilution - 15.1, Result VALID
<hr></blockquote>
I had my car diagnosed and here is what they did:
1. Check O2 Sensor - wave form ok.
2. Check fuel pressure - ok.
3. Check throttle switch - ok.
4. Pressurize intake system to locate leaks - found leaks and repaired.
5. Check emissions with O2 sensor not connected -
Before the CAT: HC 150 ppm, CO 5%
6. Set up CO and base idle and recheck -
Before the CAT: HC 120 ppm, CO 3%
!NOTE! CO will not adjust below 3% - suspect faulty air flow meter.
7. Check emissions with O2 sensor connected -
Before the CAT: HC 94 ppm, CO 0.4%
After the CAT: HC 43 ppm, CO 0.09%
8. Emissions Re-Test - results: PASS!
Cost: $304 Labour + $10.64 in vacuum hose + $15 Emission Re-test fee + tax = $379.08CAD ($242.29US)
I'm now 61% under the limit on HC, 34% under the limit on NOx, and 62% under the limit on CO %. Here are the detailed results of the re-test:
ASM 2525 test:
HC ppm - Limit 127, Reading 50, Result PASS.
CO % - Limit 0.71, Reading 0.27, Result PASS.
NO ppm - Limit 1415, Reading 934, Result PASS.
RPM - 2510, Result VALID
Dilution - 14.76, Result VALID
Curb Idle test:
HC ppm - Limit 300, Reading 36, Result PASS.
CO % - Limit 1.50, Reading 0.06, Result PASS.
NO ppm - Limit N/A, Reading N/A, Result N/A.
RPM - 836, Result VALID
Dilution - 14.66, Result VALID
Very surprised that intake vacuum leaks caused my car to originally fail with such high readings.
The black rubber Y-connectors and L-connectors that connect the hard plastic vacuum lines found on the fuel pressure regulator and damper, cycling valve, cut-off valve, intake manifold, bottom of the throttle body, etc were replaced with T-connectors and flexible rubber-fabric-wrapped vacuum hose. Intake plumbing was also taken apart and carefully put back together.
Regards,
Jim
...I'm 58% over the limit on HC ppm, and 49% over the limit on NOx ppm....
ASM 2525 test:
HC ppm - Limit 127, Reading 201, Result FAIL.
CO % - Limit 0.71, Reading 0.64, Result PASS.
NO ppm - Limit 1415, Reading 2109, Result FAIL.
RPM - 1686, Result VALID
Dilution - 14.6, Result VALID
Curb Idle test:
HC ppm - Limit 300, Reading 154, Result PASS.
CO % - Limit 1.50, Reading 1.20, Result PASS.
NO ppm - Limit N/A, Reading N/A, Result N/A.
RPM - 1364, Result INVALID
Dilution - 15.1, Result VALID
<hr></blockquote>
I had my car diagnosed and here is what they did:
1. Check O2 Sensor - wave form ok.
2. Check fuel pressure - ok.
3. Check throttle switch - ok.
4. Pressurize intake system to locate leaks - found leaks and repaired.
5. Check emissions with O2 sensor not connected -
Before the CAT: HC 150 ppm, CO 5%
6. Set up CO and base idle and recheck -
Before the CAT: HC 120 ppm, CO 3%
!NOTE! CO will not adjust below 3% - suspect faulty air flow meter.
7. Check emissions with O2 sensor connected -
Before the CAT: HC 94 ppm, CO 0.4%
After the CAT: HC 43 ppm, CO 0.09%
8. Emissions Re-Test - results: PASS!
Cost: $304 Labour + $10.64 in vacuum hose + $15 Emission Re-test fee + tax = $379.08CAD ($242.29US)
I'm now 61% under the limit on HC, 34% under the limit on NOx, and 62% under the limit on CO %. Here are the detailed results of the re-test:
ASM 2525 test:
HC ppm - Limit 127, Reading 50, Result PASS.
CO % - Limit 0.71, Reading 0.27, Result PASS.
NO ppm - Limit 1415, Reading 934, Result PASS.
RPM - 2510, Result VALID
Dilution - 14.76, Result VALID
Curb Idle test:
HC ppm - Limit 300, Reading 36, Result PASS.
CO % - Limit 1.50, Reading 0.06, Result PASS.
NO ppm - Limit N/A, Reading N/A, Result N/A.
RPM - 836, Result VALID
Dilution - 14.66, Result VALID
Very surprised that intake vacuum leaks caused my car to originally fail with such high readings.
The black rubber Y-connectors and L-connectors that connect the hard plastic vacuum lines found on the fuel pressure regulator and damper, cycling valve, cut-off valve, intake manifold, bottom of the throttle body, etc were replaced with T-connectors and flexible rubber-fabric-wrapped vacuum hose. Intake plumbing was also taken apart and carefully put back together.
Regards,
Jim
07-24-2002, 08:27 PM
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oh how i enjoy living in FL now (no emissions testing).. and uptstae NY previous to that (emissions testing = visual inspection of cat)
there is NO WAY at all that my 924 will EVER pass emissions in ANY state
there is NO WAY at all that my 924 will EVER pass emissions in ANY state
07-28-2002, 03:33 PM
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Hi,
Glad to hear that you passed emissions. How did they pressureize the intake system? Where was the pressure applied and how much pressure. I still have high NOx.
Thanks,
Steve
Glad to hear that you passed emissions. How did they pressureize the intake system? Where was the pressure applied and how much pressure. I still have high NOx.
Thanks,
Steve
07-28-2002, 11:26 PM
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Search for "pressurizing intake" on this forum for topics on this...
The factory manual uses a fuel filter that is cut in half and has an air valve that you can use to introduce air pressure through. It's inserted into the boot that the air flow meter attaches to.
944 Turbo supplement, page 28-41, Test Point 13 - Intake Pressure System Sealing:
1. Check all connection points after air flow sensor for tight fit and sealing.
2. Using the locally-made tool (see Workshop Manual 944, page 24-15), build up 0.5 bar pressure in intake system and check sealing.
Regards,
Jim
The factory manual uses a fuel filter that is cut in half and has an air valve that you can use to introduce air pressure through. It's inserted into the boot that the air flow meter attaches to.
944 Turbo supplement, page 28-41, Test Point 13 - Intake Pressure System Sealing:
1. Check all connection points after air flow sensor for tight fit and sealing.
2. Using the locally-made tool (see Workshop Manual 944, page 24-15), build up 0.5 bar pressure in intake system and check sealing.
Regards,
Jim
07-29-2002, 01:26 AM
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It looked like a vacuum leak from the beginning.
I would never do those stupid @$$ tricks to pass emissions tests. Bad emissions is an indication of a poor running engine. A poor running engine puts out less power. Since you bought a 951, I would assume you (and others on the list) like power. Lean mixtures run very hot. Congrads for spending the money and fixing the problem before you toasted your rings, overheated spark plugs, and killed your cat.
I would never do those stupid @$$ tricks to pass emissions tests. Bad emissions is an indication of a poor running engine. A poor running engine puts out less power. Since you bought a 951, I would assume you (and others on the list) like power. Lean mixtures run very hot. Congrads for spending the money and fixing the problem before you toasted your rings, overheated spark plugs, and killed your cat.
