Emissions problem on my audi.

[monsterhunter]

Well guys, i have been constitly(SP?) failing emission while im trying to get this car to pass inspection. its the only thing im failing and i need some help here. i just bought a new cat, but i put it all the way back where the tailpipe should be. the HCs went down almost to passing but the COS went way up.my main question is; Since the cat is that far away from the motor is that whats causing the COS to go up? Or is there something else wrong? The car is a 1992 audi 100 quattro 2.8L with 187k on it. any question to help out just ask. and il try my best to answer it.



Thanks in advance Jay.

[BoostAddicted]

I have a question, is the area you put the cat in stock location ?? if not.. ill have explaining to do that might help

[Lucky7]

Off hand I am going to say it is not the stock location. That far back it is likely not getting the heat required to do the job?

[zippo855]

i am going to have to say that with the cat that far away from the motor 2 things are happening. 1, as mentioned, it is not heating up to the required temp to acutally burn off the excess fuel vapor. and 2, if you car has O2 sensors, as most cars did. The are usually before and after the cat in the stock location. By it not being in the stock location the O2 sensors arent getting a reading for whether or not it is running too rich, lean, etc.

[BoostAddicted]

Originally Posted by zippo855

i am going to have to say that with the cat that far away from the motor 2 things are happening. 1, as mentioned, it is not heating up to the required temp to acutally burn off the excess fuel vapor. and 2, if you car has O2 sensors, as most cars did. The are usually before and after the cat in the stock location. By it not being in the stock location the O2 sensors arent getting a reading for whether or not it is running too rich, lean, etc.

exactly what i was gonna say.. The O2 sensors are giving the ECU wrong A/F mixtures. its probly running to rich, when the O2 sensors dont sense that heat they tell the ECU to squirt more fuel in there to make up for that heat. and all its doing is confusing the whole cars ECU and function over all.. you need to put it back in the correct location. and then drive the car around so the ECU gets used to the old days.

good luck

[jimmythekid1]

Originally Posted by Lucky7

Off hand I am going to say it is not the stock location. That far back it is likely not getting the heat required to do the job?

I would have to agree, that is a good starting point. The O2 should not be an issue seeing that most pre 1992 cars only had o2 sensors before the cat.

[BoostAddicted]

Originally Posted by jimmythekid1

I would have to agree, that is a good starting point. The O2 should not be an issue seeing that most pre 1992 cars only had o2 sensors before the cat.

im pretty sure all cars O2 sensors are before the cats. cuz both my cars and my moms car have it before the cats. Its mainly just for recording heat. so yeah.. but im confused on why he moved it so far back..

[BART]

Originally Posted by BoostAddicted

im pretty sure all cars O2 sensors are before the cats. cuz both my cars and my moms car have it before the cats. Its mainly just for recording heat. so yeah.. but im confused on why he moved it so far back..

It has nothing to do with recording heat, it measures oxygen content in the exhaust and all cars that are OBD2 have them both before and after the cat. I will also agree with all those above that having the cat that far back will not let it work efficiently. Being a 92 it will most likely only have one o2 sensor.

[jimmythekid1]

Originally Posted by BART

It has nothing to do with recording heat, it measures oxygen content in the exhaust and all cars that are OBD2 have them both before and after the cat. I will also agree with all those above that having the cat that far back will not let it work efficiently. Being a 92 it will most likely only have one o2 sensor.

Very true, how ever a vehicle with more then one bank such as a v6 may use two oxygen sensors after each maniflold. But even most v6 have a Y pipe connecting both maniflod with one sensor after the Y. But some with dual exhaust would of had two PRE cat o2 sensors.

[BART]

Originally Posted by jimmythekid1

Very true, how ever a vehicle with more then one bank such as a v6 may use two oxygen sensors after each maniflold. But even most v6 have a Y pipe connecting both maniflod with one sensor after the Y. But some with dual exhaust would of had two PRE cat o2 sensors.

I should have clarified, I meant one per bank on pre OBD2 and 2 per bank (pre and post cat) on OBD2.

[BoostAddicted]

Originally Posted by BART

It has nothing to do with recording heat, it measures oxygen content in the exhaust and all cars that are OBD2 have them both before and after the cat. I will also agree with all those above that having the cat that far back will not let it work efficiently. Being a 92 it will most likely only have one o2 sensor.

Well from what ive learned in auto tech.. the main way the O2 sensors know your AF mixture in generally bassed off heat. the higher the heat the leaner the A/F mixture is.. the Lower the heat, the richer it gets.

[BART]

Chemical reaction, nothing to do with EGT.

http://auto.howstuffworks.com/question257.htm

[BoostAddicted]

Originally Posted by BART

Chemical reaction, nothing to do with EGT.

http://auto.howstuffworks.com/question257.htm

ehh, dont feel like reading all that. all im saying is thats what ive learned in school. My teacher was telling me about it. he said that chemical reaction does have a part in it. But Exhaust heat helps determine the A/F ratio.

[jimmythekid1]

Originally Posted by BoostAddicted

Well from what ive learned in auto tech.. the main way the O2 sensors know your AF mixture in generally bassed off heat. the higher the heat the leaner the A/F mixture is.. the Lower the heat, the richer it gets.

Well giving my professional opinon you need to find a new school or listen better.

Originally Posted by BoostAddicted

ehh, dont feel like reading all that. all im saying is thats what ive learned in school. My teacher was telling me about it. he said that chemical reaction does have a part in it. But Exhaust heat helps determine the A/F ratio.

the only thing heat does is help the oxygen sensor work better. Exhaust gas is general a constant temp as long as no misfires are occurring.

[BoostAddicted]

Originally Posted by jimmythekid1

Well giving my professional opinon you need to find a new school or listen better.

quote=BoostAddicted;234984]ehh, dont feel like reading all that. all im saying is thats what ive learned in school. My teacher was telling me about it. he said that chemical reaction does have a part in it. But Exhaust heat helps determine the A/F ratio.

the only thing heat does is help the oxygen sensor work better. Exhaust gas is general a constant temp as long as no misfires are occurring.[/QUOTE]

well im looking for no arguments.. but if your "professional" and your saying exhaust gas temps stay the same i dont believe that.. the more fuel. the hotter the exhaust gets. and vise versa, depending on air concentration around you the car is adjusting its fuel mixture, thus causing elevating or lowering of EX temps. this is only my opinion... im not saying i KNOW this.. but this is what i strongly believe. i could never imagine a cars exhaust staying the same temp at all.

[jimmythekid1]

Originally Posted by BoostAddicted

the only thing heat does is help the oxygen sensor work better. Exhaust gas is general a constant temp as long as no misfires are occurring.

well im looking for no arguments.. but if your "professional" and your saying exhaust gas temps stay the same i dont believe that.. the more fuel. the hotter the exhaust gets. and vise versa, depending on air concentration around you the car is adjusting its fuel mixture, thus causing elevating or lowering of EX temps. this is only my opinion... im not saying i KNOW this.. but this is what i strongly believe. i could never imagine a cars exhaust staying the same temp at all.[/quote]

sorry wrong again actually a lean mixture can cause higher exhaust temps. For example low octane fuel causing spark knock.

A zirconia 02 sensor produces a voltage from 0 to 1 volt, when it is induced to oxygen.

a titania 02 work similar however the pcm runs 1 volt to the sensor and will the induction of oxygen it creates sort of a variable resistor. Producing a signal from 0 to 1 volt.

However none of this can happen with out heat to help the chemical reaction while oxygen passes by the the sensors core. This information I'm sure is what you misunderstood your instructor say.

That is also why late model o2 sensors have heater built in to help it work faster.

Your also right about the exhaust temp changing as it will as the engine warms up and threw out the different rpm ranges. But the change it not constant, and know way can fuel trim be calculated by it.

[BoostAddicted]

Originally Posted by jimmythekid1

well im looking for no arguments.. but if your "professional" and your saying exhaust gas temps stay the same i dont believe that.. the more fuel. the hotter the exhaust gets. and vise versa, depending on air concentration around you the car is adjusting its fuel mixture, thus causing elevating or lowering of EX temps. this is only my opinion... im not saying i KNOW this.. but this is what i strongly believe. i could never imagine a cars exhaust staying the same temp at all.

sorry wrong again actually a lean mixture can cause higher exhaust temps. For example low octane fuel causing spark knock.

A zirconia 02 sensor produces a voltage from 0 to 1 volt, when it is induced to oxygen.

a titania 02 work similar however the pcm runs 1 volt to the sensor and will the induction of oxygen it creates sort of a variable resistor. Producing a signal from 0 to 1 volt.

However none of this can happen with out heat to help the chemical reaction while oxygen passes by the the sensors core. This information I'm sure is what you misunderstood your instructor say.

That is also why late model o2 sensors have heater built in to help it work faster.

Your also right about the exhaust temp changing as it will as the engine warms up and threw out the different rpm ranges. But the change it not constant, and know way can fuel trim be calculated by it.[/QUOTE]

ive always had rich and lean confused with each other. for some reason ive always gotten them mixed up. But thats the same idea i ment. but like you said heat helps the reaction. i never said heat was the ONLY thing that the o2 sensor reads. i simply said heat helps it determine A/F mixture. and i dont know much about OBDII cars. both my cars are OBDI and i work on them all the time and never get any problem so for me. it works. ive only been into cars about 2 years now. so i have lots to learn.

[jimmythekid1]

ah boy....

well good luck moster hunter on getting that machine to pass

[Action B]

Originally Posted by BoostAddicted

sorry wrong again actually a lean mixture can cause higher exhaust temps. For example low octane fuel causing spark knock.

This is the case. Lean fuel mixtures cause high temp exhaust gas.

Also, wideband and shortband o2 sensors do not read heat, they do have a heat range where they are more accurate, but they do not read heat. I can tell you this for sure because I have a wideband AEM UEGO guage in my car that does not correspond to my EGT guage.

I think the reason your failing your emissions is probably due to the catalytic converter placement. Catalytic converters work better when they are WARMER, the further back on the exhaust you have that cat the cooler its going to be due to heat dissipation. If it doesn't get to the appropriate heat range then it will be less efficient.

This is why you can often times lower your emissions on those tests by driving your car around on the highway for awhile to really heat that catalytic converter up.

[monsterhunter]

All right so, after my 12 hours of work on my friends 67 Stang(or as he bages FO D MUSTA G) we did a complete over haul on the 4 wheel drum brakes, after figuring out what parts were wrong and what not we got it all done faster...ANYWAY, after reading through and skippin the non needed arguing stuff. i have this stuff to say: 1. NEED to move the cat to near the stock ones(There is a universal one on it, due to only being able to get D.R's off line) and 2. I need to run alittle more Zmax and 3. run 93 octane(im runing 89 which is lower then it calls for[91 or higher]) And then we shall see what happens.
[QUOTE]well good luck moster hunter on getting that machine to pass/QUOTE]
and lastly, thank you, and Thanks everyone for all the help.