View Full Version : help with emissions test

28th November 2006, 16:34
My girlfriend just had her 2001 corolla in for emissions test here in Ontario, Canada. It failed and now it is my task to fix it somehow ( so she tells me :suprised: )
it is a 4 cylinder 1.8L engine ~120.000KM on it.

the test results were as follows:
HC [35/72] pass
CO [0.10/0.40] pass
NO [43/550] pass

HC [245/150] fail
CO [1.37/0.70] fail
NO [__/__] ___

now from what I understand, this means it is not burning the fuel properly at idle, so I have to look for reasons for it to not burn the fuel properly.

I checked the air filter, and it defenitely needs changing.. could an air filter alone cause such readings?
I also plan to check the spark plugs, but that requires more tools than I have handy. Will visit a friend tomorrow who has a better selection.

Any insight on what could be causing these readings would be greatly appreciated

28th November 2006, 16:47
Is the "check engine" light on?

An O2 sensor (Oxygen Sensor, Lambda Sensor) could definitely cause this problem. Essentially what is happening here is that it's running WAY too rich at idle. You could also have an exhaust issue, I suppose. However, the O2 sensor will normally throw a "check engine" code.

Go to your local Auto Zone or similar store and borrow their OBD2 reader, plug it in, and see if there are any codes in the system... that ought to tell you what's going on.

It's almost definitely an exhaust issue, the question is whether it's an electronic bit (like a sensor) or an electro-mechanical bit (like an EGR valve) or just a plain ol' physical problem.

28th November 2006, 16:57
Check engine light is not on.. she just recently had some exhaust work done as there was a loose connection somewhere near the engine block ( did not see it, just her passing on her interpretation of what the mechanic said).. I hope they did not mess with the sensors.

since it is running fine when not in idle, which sensors are in use then compared to when in idle.. is it running open loop when ideling?

I will head to the local Canadian Tire, and see if I can borrow a code reader, if not, they have a good return policy so in effect they will lend one to me anyways ;)

28th November 2006, 17:50
Check for any disconnected or cracked vacuum lines, these will have the most effect on emmissions at an idle.
could also be a leak in the intake system somewhere.
Check the PVC valve (if equiped) - might me best to replace it anyway.
A fresh oil change won't hurt.
An exhaust leak could also do it, as Gurm suggested - you should be able to hear it if you get down on all fours and put your head under the car while it is idling.

28th November 2006, 18:41
CHange the air filter first. Yes it could.

Also a dirty air mass meter - usually have to replace with new, but do that last as they can be expensive. CHeck the wiring connector to the mass meter - make sure no oxidation in the contact area. clean with electronic parts cleaner. Don't get anything on the wire in the mass meter if you do pull it to inspect.

look for vacuum leaks - elbows are notorious, mushy vacuum lines, etc

DUmp in a bottle of fuel injector cleaner. follow the instructions on the bottle. A single fouled injector could do it. RUn out the tank. But you should feel the engine running a little rough occasionally. run out at least half the tank.

If you hear a rattle on the exhaust, the cat converter may be fouled and plugged - symptom of running rich for a while.

Exhaust leak should not be an issue - doesn't change the %O2 in the exhaust unless somehow air is being pulled in, just a CO hazard for the occupants.

COuld also be a temperature sensor on the coolant.

Ask the service manager at a dealer or a mechanic what the most common cause of rich idle is on this car at this age.

good luck.

28th November 2006, 19:30
Hmm.. I went to Canadian Tire and found that they were sold out of both air filters and code readers. I chatted with their service guy, who looked over the numbers and said that it was close to passing. Since it was doing fine at higher speed, the O2 sensors etc would be OK, and the NO was really low so the catalytic converter was doing its thing too. He recommended some fuel additive and told me to find a new filter before the test.
I will try looking for vacuum hose leaks and the PCV valve tomorrow when it is light out.. hopefully I can spot something simple :)

Thanks everyone.. I will let you know how it goes on Thursday :up:

29th November 2006, 02:36
I have no clue about cars, but don't they always recommend fuel additives? Doesn't modern brand-name fuel already contain all the needed additives, anyway? What did he say would the additive actually do?

29th November 2006, 04:13
the addiditves are normally used to clean the fuel system , ie the injectors.
If the injectors are fouled, they could would not meter properly (they could dribble the fuel out instead of spraying it).
Most fuels have some aount of additives in them, but t's not unheard of the have the odd lot of 'bad' fuel.

29th November 2006, 04:53
Just checked the numbers from my last e-test on my 1988 5.0L engine with 240,000km:
HC 22/66
CO .01/.37
NO 100/757
HC 55/200
CO .01/1.0

29th November 2006, 18:12
Usually it is a piece of dirt or rust from the tank that gets the injector. most fuels have decent cleaners in them already. The extra dose is to get rid of any plaques that have built up. We are now seeing problems in the US because of all the ethanol being used - some is coming in with higher water and rust from the storage tanks. We are changing fuel filters more often as a result.

30th November 2006, 11:23
Looks fine now, but make sure the engine is hot before having any emissions tests done... particularly with older cars where the cats have lower efficiency.. If the catalyst isn't up to temp then it can do exactly what you saw... work at higher speeds (because of the hotter exhaust) but not at idle because it is still relatively cool so isn't fully functioning.

30th November 2006, 15:56
so last night I cleaned the PCV valve, not that it was terribly dirty, checked the vacuum lines, which all looked good, so basically all that happened was a change in the air filter.

New Readings:
HC [13/72] pass
CO [0.02/0.40] pass
NO [8/550] pass

HC [136/150] Pass
CO [0.69/0.70] Pass
NO [__/__] ___

the car passed, even if it just squeaked in under the line, but it is a pass :D

amazing what difference a dirty air filter can make :)

30th November 2006, 16:31