Failed Emissions in my 98 corolla

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
NOx levels were too high.

levels were:
HC .23 out of 1.2
CO 5.65 out of 15.00
CO2 was 290.0815
NOx was 16.086 1.500


with those numbers, do you think my car is running too lean? or should I replace the cat? They guy at the emissions place didn't really tell me anything other than I failed. I've done some googling and people are saying if the HC and CO numbers are low, and the NOx is high, I might be running lean. Does anyone have more experience with this?
 

brblx

Diamond Member
Mar 23, 2009
5,499
2
0
cat should not affect nitrides of oxygen. it's mainly the job of EGR.

typically (and this is a huge generalization), hydrocarbons mean the engine is running too rich or missing (unburned fuel), carbon monoxide mean it's running too lean (excess oxygen).

check engine light it off, right? and you're sure it's functioning (should light when you turn the key to position two)?

that NOx reading is super high, but CO is only a little high. i would think plugged EGR more than a lean condition.
 
Last edited:

brblx

Diamond Member
Mar 23, 2009
5,499
2
0
fucking time travelling double posts and edits.
 
Last edited:

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
cat should not affect nitrides of oxygen. it's mainly the job of EGR.

typically (and this is a huge generalization), hydrocarbons mean the engine is running too rich or missing (unburned fuel), carbon monoxide mean it's running too lean (excess oxygen).

check engine light it off, right? and you're sure it's functioning (should light when you turn the key to position two)?

that NOx reading is super high, but CO is only a little high. i would think plugged EGR more than a lean condition.

yeah my check engine light works, but isn't on. i had a faulty o2 sensor that i replaced last week and my check engine light went away. is it possible to run carb cleaner through the car and clean out the EGR?


edit: nice self time warp
 
Last edited:

AMCRambler

Diamond Member
Jan 23, 2001
7,711
30
91
I think you're going to want to take the EGR off to clean it. It wasn't hard on my 1990 Accord. There was a fitting running into one side of it that I had to disconnect and then two bolts holding it to the head. A tooth brush and some carb cleaner on it and put it back together should help.

You can also try cleaning the MAF sensor. This one you gotta be real careful with though cuz it's got tiny wires. Troubleshooting emissions problems is a pain in the ass though because you can't just test it yourself and know that you've fixed it. Might be worth taking it to a shop. They'll have the equipment to test it as they try different things.
 

PricklyPete

Lifer
Sep 17, 2002
14,582
162
106
Impossible...it's a Toyota.

I agree with AMCRambler...try removing the EGR and clean it...shouldn't be hard.
 

Zargon

Lifer
Nov 3, 2009
12,218
2
76
You can also try cleaning the MAF sensor. This one you gotta be real careful with though cuz it's got tiny wires. Troubleshooting emissions problems is a pain in the ass though because you can't just test it yourself and know that you've fixed it. Might be worth taking it to a shop. They'll have the equipment to test it as they try different things.

they have MAF cleaning spray now, but I have zero experience with it.
 

MovingTarget

Diamond Member
Jun 22, 2003
9,002
115
106
Sounds like the EGR valve or the MAF sensor, like many have mentioned. Barring that, you could always move to a state that doesn't have such nonsense...
 

kornphlake

Golden Member
Dec 30, 2003
1,567
9
81
does a 98 corolla have an EGR? My 01 Sienna doesn't, but it's an entirely different engine.

As far as I know the only way to clean the egr is to remove it and scrub it, carb cleaner spray may get rid of some of the junk but to get it really clean you'll have to scrub it. You should notice improved performance with a properly functioning EGR.
 

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
does a 98 corolla have an EGR? My 01 Sienna doesn't, but it's an entirely different engine.

As far as I know the only way to clean the egr is to remove it and scrub it, carb cleaner spray may get rid of some of the junk but to get it really clean you'll have to scrub it. You should notice improved performance with a properly functioning EGR.


yeah its got an EGR but doesn't have a MAF. ill try to work on it today, and take it back to get emissions done.
 

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
i cleaned it, and ran carb cleaner through it, but when i was driving home the check engine light came on....i checked it when i got home and one of the hoses leading into my intake was kinked so i unkinked it but the check engine light stilll stayed on, do i have to reset the battery for it to clear?
 

fleabag

Banned
Oct 1, 2007
2,450
1
0
i cleaned it, and ran carb cleaner through it, but when i was driving home the check engine light came on....i checked it when i got home and one of the hoses leading into my intake was kinked so i unkinked it but the check engine light stilll stayed on, do i have to reset the battery for it to clear?
Disconnecting and reconnecting the battery will NOT I repeat, will NOT reset a check engine light especially on an OBD-II car. The light may disappear but the code is stored and you have to use a tool in order to reset it. Now if you had an OBD-I car, you probably could've used a paper clip.
 

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
Disconnecting and reconnecting the battery will NOT I repeat, will NOT reset a check engine light especially on an OBD-II car. The light may disappear but the code is stored and you have to use a tool in order to reset it. Now if you had an OBD-I car, you probably could've used a paper clip.

alright just making sure, im gonna have to take it somewhere and have to code scanned. idk wtf it could be. everything was done legit. i think my EGR might just be dead or something.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Disconnecting and reconnecting the battery will NOT I repeat, will NOT reset a check engine light especially on an OBD-II car. The light may disappear but the code is stored and you have to use a tool in order to reset it. Now if you had an OBD-I car, you probably could've used a paper clip.

This is, of course, not entirely true.
 

fleabag

Banned
Oct 1, 2007
2,450
1
0
This is, of course, not entirely true.
You're such a moron, you're only making yourself look stupid.

alright just making sure, im gonna have to take it somewhere and have to code scanned. idk wtf it could be. everything was done legit. i think my EGR might just be dead or something.
Or it could be you messed up your MAF when you poured in that carb cleaner crap.
 

jlee

Lifer
Sep 12, 2001
48,518
223
106
You're such a moron, you're only making yourself look stupid.
http://www.obd-codes.com/faq/reset_obd_codes.php
OBD-Codes.com
Your OBD-II Trouble Codes Repair Site
FAQ: How do I reset the "Check Engine" Light?
After you've properly diagnosed and fixed the problem that triggered the OBD trouble code, you can reset or clear the Check Engine / Service Engine Soon light by one of two methods.

Note: The code (i.e. CEL / SES light) will usually go away after a certain number of driving cycles, perhaps a few days. You can choose to wait it out or follow one of these methods.

The cheap, easy, free method
Simply disconnect your battery, turn on the headlight switch for about five to ten minutes, and re-connect the battery. This is pretty simple, but will likely result in you losing your radio presets and perhaps some other small things like that.


Using a scan tool
Most if not all scan tools have an option to clear or reset codes without the use of any tools or touching the battery. Consult your tool's manual for information on how to do it with your particular model.
 

fleabag

Banned
Oct 1, 2007
2,450
1
0
What the fuck? How is turning the light switch on and disconnecting the battery even related? That's completely absurd! So absurd, that I've got to try it! :D The reason I know that disconnecting the battery doesn't reset codes is not only have I been told, but every vehicle I've worked on, OBD-I or OBD-II while may hide the check engine light, but when you ask if it has any codes, it always remembers them with the only way of getting rid of the code is to reset it by either using a tool or shorting two pins.
 

jlee

Lifer
Sep 12, 2001
48,518
223
106
Maybe it sucks out any possible residual power from the electrical system? I've never turned the headlights on..disconnecting the battery has always reset the light for me. I don't care if it remembers a code as long as there's no active problem. If there's an active problem, the light should be on.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
It would discharge any capacitors that might be maintaining power, I suppose.

It's my understanding that some codes are stored and some are not, which is why is said "not entirely true". Some are nonvolatile, and some are not.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Remember fleabag, you specifically said it would not reset the light...

You did not say it would not clear the code...
 

HybridSquirrel

Diamond Member
Nov 20, 2005
6,161
2
81
I don't have a MAF, thats why i used the carb cleaner. Ill go try disconnecting the battery, i have to drive a few hours tonight so hopefully it will go away on its own. I think the problem was that it didnt fully burn off all the carb cleaner.
 

SSSnail

Lifer
Nov 29, 2006
17,458
83
86
I don't know who made your 98' Corolla, but it doesn't have an EGR valve. NOx, or OXIDES of NITROGEN (not the other way around), is typically created when the internal combustion temperature reaches 2500 degrees F (or exceed it). This condition can be caused by many things, carbon build-up, lean running condition, ECT malfunctioning, etc... (anything that makes the engine runs hotter).

Scan a picture of your Vehicle Inspection Report and post it here, I may be able to tell you a bit better about what it's doing.

And yes, you can reset the CEL by disconnecting the battery terminals (for good measures, touch the negative and positive cables to discharge any capacitors in the system). The reasons why you'd fail for the CEL is because it's an automatic fail for the visual inspection, regardless of the cause. As long as the CEL is not on at the time of inspection, and you have no more than two emission related continuous monitors incomplete, you can pass provided that your emission equipments are functioning properly.

From the numbers you posted, I can't decipher what is what, as HC and NOx are measured in ppm (parts per million) and the other 3 gases are measured by percentage, you also didn't post the O2 percentage as that is also a good indicator of how your engine is performing, correlating to the other four gases.

Pics or BAN!
 

ayabe

Diamond Member
Aug 10, 2005
7,449
0
0
What the fuck? How is turning the light switch on and disconnecting the battery even related? That's completely absurd! So absurd, that I've got to try it! :D The reason I know that disconnecting the battery doesn't reset codes is not only have I been told, but every vehicle I've worked on, OBD-I or OBD-II while may hide the check engine light, but when you ask if it has any codes, it always remembers them with the only way of getting rid of the code is to reset it by either using a tool or shorting two pins.

So your mom lets you perform maintenance on the Lexus? Doubt it.