Help! Keeps failing emissions test.

[EduardoP0520]

Hello everyone.
I have a 2009 subaru Impreza 2.0r N/A (the mexican version of the 2.5) that keeps failing the emissions test due to high HC at idle. The limit is 100 ppm, my car got 109 ppm.

Idle measured (limit): HC 109 ppm (100 ppm), CO 0.23% (1.0%), CO+CO2 14.7% (16.5%), O2 00.6% (2.0%), lambda 01.02, RPM 814
2500 RPMs measured (limit): HC 40 ppm (100 ppm), CO 0.12% (1.0%), CO+CO2 15.2% (16.5%) O2 00.1% (2.0%), lambda 1.0, RPM 2549.

I already changed the oil, air filter, spark plugs (ngk iridium), cleaned the MAF sensor, took the fuel injectors to get cleaned and analysed, ran some catalytic convertor cleaner (Liqui Moly), put some premium unleaded fuel (91 octane in Mexico) and drove it hard for about 20 minutes before the test (half to full throttle until 6500 rpms). It failed before due to the same reason, high HC at idle (never over 200 PPM). What would you suggest? What could be causing this emissions failure?

I'd appreciate the help.

 

[bmart]

I'll google for you...

What Causes High Hydrocarbon (HC)? | SmogTips.com

Below are common failures which are likely to produce high Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible...

www.smogtips.com

What could cause high HC and CO, but low NO and CO2 in a smog test

Despite my confidence in having a (relatively) new catalytic converter and a new O2 sensor, my lovely 1994 BMW 325i Convertible got flagged as a "Gross Polluter." The test results are summarized be...

mechanics.stackexchange.com

 

[EduardoP0520]

I'll google for you...

What Causes High Hydrocarbon (HC)? | SmogTips.com

Below are common failures which are likely to produce high Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible...

www.smogtips.com

What could cause high HC and CO, but low NO and CO2 in a smog test

Despite my confidence in having a (relatively) new catalytic converter and a new O2 sensor, my lovely 1994 BMW 325i Convertible got flagged as a "Gross Polluter." The test results are summarized be...

mechanics.stackexchange.com

Thank you for the googling, I've done quite a bit myself. The second post you reference is actually with high HC and CO, while my car only has high HC and low CO, which is quite the opposite.

Thanks, still.

 

[Grumpy1950]

First post above references possible intake leaks or vacuum leaks. Perhaps a smoke test could help find something. Basically what this involves is hooking up a smoke generator machine and looking for leaking smoke from hoses, intake system joints etc.

 

[Dick Foster]

Could be your CAT is trash.
It doesn't take much to consign a CAT to the trash heap. Oil consumption, manifold leaks, fuel regulators, bad O2 sensors, etc.

 

[Raymond3006]

Hello everyone.
I have a 2009 subaru Impreza 2.0r N/A (the mexican version of the 2.5) that keeps failing the emissions test due to high HC at idle. The limit is 100 ppm, my car got 109 ppm.

Idle measured (limit): HC 109 ppm (100 ppm), CO 0.23% (1.0%), CO+CO2 14.7% (16.5%), O2 00.6% (2.0%), lambda 01.02, RPM 814
2500 RPMs measured (limit): HC 40 ppm (100 ppm), CO 0.12% (1.0%), CO+CO2 15.2% (16.5%) O2 00.1% (2.0%), lambda 1.0, RPM 2549.

I already changed the oil, air filter, spark plugs (ngk iridium), cleaned the MAF sensor, took the fuel injectors to get cleaned and analysed, ran some catalytic convertor cleaner (Liqui Moly), put some premium unleaded fuel (91 octane in Mexico) and drove it hard for about 20 minutes before the test (half to full throttle until 6500 rpms). It failed before due to the same reason, high HC at idle (never over 200 PPM). What would you suggest? What could be causing this emissions failure?

I'd appreciate the help.

Looked thru the "help" answers, maybe what is being overlooked MIGHT be a poorly performing THERMOSTAT ... ???

 

[keith3267]

Does your car have OBD II?
Are you being tested in the US or Mexico?
If you have OBD II, do you have a check engine light?
Have you had a code reader plugged in to read codes?
If so, were there any codes?
What were they?
You may need to replace your front oxygen sensor(s).

 

[Mark Monte]

Oh man, your car is so very close to passing. I feel your pain. Is the air filter new?
The temperature sensor is a possibility because the engine might be running rich if the sensor is reporting that the engine is still cold, the computer will automatically enrichen the mixture when it thinks the engine is still cold (fuel injector duty cycle). Hyrdrocarbons are formed when oil is burnt in the combustion chamber and creates soot. This usually happens when the engine runs too rich.
It is the job of the CAT to eat those extra HCs, so that might be a factor, too. You are so very close at 109 HC!
Sometimes a slightly higher idle speed can help, but Idle speed is set automatically by the computer, but you have an allowable margin for a higher idle speed. *Set the idle screw slightly higher by opening the throttle plate very slightly.
If oil is entering the combustion chamber from either the valve guides or getting past the rings, then you might try an oil additive like STP Oil Treatment or Hyperlube. How many miles are on the engine? https://rislone.com/products/hy-per-lube-zinc-zddp-supplement/

 

[Raymond3006]

Oh man, your car is so very close to passing. I feel your pain. Is the air filter new?
The temperature sensor is a possibility because the engine might be running rich if the sensor is reporting that the engine is still cold, the computer will automatically enrichen the mixture when it thinks the engine is still cold (fuel injector duty cycle). Hyrdrocarbons are formed when oil is burnt in the combustion chamber and creates soot. This usually happens when the engine runs too rich.
It is the job of the CAT to eat those extra HCs, so that might be a factor, too. You are so very close at 109 HC!
Sometimes a slightly higher idle speed can help, but Idle speed is set automatically by the computer, but you have an allowable margin for a higher idle speed. *Set the idle screw slightly higher by opening the throttle plate very slightly.
If oil is entering the combustion chamber from either the valve guides or getting past the rings, then you might try an oil additive like STP Oil Treatment or Hyperlube. How many miles are on the engine? https://rislone.com/products/hy-per-lube-zinc-zddp-supplement/

Most of these "possibles" can be checked by LIVE MONITORING of the OBD-2 World as presented by Subaru ; especially on the data stored from recent operations ... !!!!

 

[Dick Foster]

Does your car have OBD II?
Are you being tested in the US or Mexico?
If you have OBD II, do you have a check engine light?
Have you had a code reader plugged in to read codes?
If so, were there any codes?
What were they?
You may need to replace your front oxygen sensor(s).

Every car made since 1996 must have OBDII. It was made a legal requirement to sell a car in the USA then.

 

[RonC6]

If this were me, I'd consider changing the front O2 sensor because it regulates the Air-Fuel mixture. I'd also consider a short spacer on the rear O2 to reduce it's sensitivity. The later has worked well for me. I avoid changing CAT because, only an aftermarket is "affordable" and I suspect the OEM is more likely a better product. G'luck

 

[Dick Foster]

If this were me, I'd consider changing the front O2 sensor because it regulates the Air-Fuel mixture. I'd also consider a short spacer on the rear O2 to reduce it's sensitivity. The later has worked well for me. I avoid changing CAT because, only an aftermarket is "affordable" and I suspect the OEM is more likely a better product. G'luck

If it helps any, Suburu does not make catalytic converters and little if anything else that makes up the cars they sell. Nor do any of the other car brands.

 

[RonC6]

Right, but pretty sure they specify the requirements for their suppliers. I use the half-shafts as an example.. I bought aftermarket and they were lifetime, but I had to change way too often. Would have been better off servicing the OEM with new boots and grease. That said, switching to Cardona brand has been good. I doubt the amount of precious metal in the after market CAT (with no requirements) is the same as those built to meet Subaru specs. Just my opinion.