Failed hydrocarbon emissions test

[nemodat]

I live in Vancouver, British Columbia, and my 1993 Camry (4 cyl auto) just failed the hydrocarbons test. Car has 358k km (about 220k miles).

I was measured at .8040 g/km, and the max allowed is .500. Two years ago, I passed by adding a $10 “guaranteed pass” additive, and taking the car for a long drive. I did both these things this time and still failed (but I only drove 125km instead of the 250k prescribed so not sure if that would make the difference).

One auto shop I spoke with charges $150 just to perform diagnostics. I don’t have much money, and I would only be able to do basic mechanical stuff on my own. As we have California-like requirements, I’m afraid that the catalytic might be shot and probably expensive to replace.

Would be grateful for any suggestions on how to tackle this, with a mind to taking cheapest steps first, and spending more money as required.

Thanks,
ND

[fenixus]

first check or replace the PCV valve sitting on the valve cover and connected by hose to intake manifold. it's a $5 part in local auto parts store (a little more for OEM part at dealer). the valve should come up (pull/twist it out by hand) after you unplug the clamp and remove hose from it.

it actually might be necessary to get the gasket/seal from dealer for that as they become brittle with age and come apart upon removal, so be careful, don't drop it into the top cylinder head. old PCV valve gasket does not provide enough sealing and will let the air through (no good).

PCV valve does majority of work in reducing HC.

There is also another side of the PCV system which is just a simple rubber hose connecting the other side of valve cover (opposite valve cover on V6, on 2.2L it's the same one, but opposite side of it) back to intake air hose. over there you simply check the hose for cracks, if it's brittle or cracked on ends then replace it, if looking good and sitting tight, just leave it.

there is also another kind of HC, called evaporated HC and that is reduced by EVAP system. I seriously doubt this is your problem though, because faulty EVAP triggers a CEL (error code) very fast, computer uses very precise detection mechanism to monitor it.

You might do the easy part and order a new fuel tank gas cap with new seal (o-ring) from dealer and get that replaced ahead to make sure you have no tiny vacuum leaks from there. total cost around $15 online or around $25 at dealer (in USA).

The third part of job on reducing HC is done by catalytic converter among other things it does like reducing also CO and NOx, so if the other two are looking good then chances are the cat converter is fine (and do not let anybody touch it).

[CTG]

We have the IM240 test here. Dyno simulated 240 second driving cycle.
I failed high on HC and replaced the cat myself. Passed with flying colors.

Try making sure you have good clean oil, maybe even do the BG 109 flush on your engine to wake the rings up some. Run some BG 44k through the tank and some Sea-Foam in the intake. Make sure your plugs, wires, cap, and rotor are good.

Beyond that, if its not a mechanical issue its usually the cat.

[nemodat]

Originally Posted by fenixus

first check or replace the PCV valve sitting on the valve cover and connected by hose to intake manifold. it's a $5 part in local auto parts store (a little more for OEM part at dealer). the valve should come up (pull/twist it out by hand) after you unplug the clamp and remove hose from it.

it actually might be necessary to get the gasket/seal from dealer for that as they become brittle with age and come apart upon removal, so be careful, don't drop it into the top cylinder head. old PCV valve gasket does not provide enough sealing and will let the air through (no good).

PCV valve does majority of work in reducing HC.

There is also another side of the PCV system which is just a simple rubber hose connecting the other side of valve cover (opposite valve cover on V6, on 2.2L it's the same one, but opposite side of it) back to intake air hose. over there you simply check the hose for cracks, if it's brittle or cracked on ends then replace it, if looking good and sitting tight, just leave it.

CTG: Very helpful, thanks. Two follow-up questions...

If gasket material falls through valve cover, any idea of the risk or severity of damage? At least one poster got away with it but perhaps he had a horseshoe

Second, the Toyota dealer garage said often the hoses connected to PCV get clogged and thay can often fix problem without even needing to replace PCV itself. Does that sound credible? Just wondering if I might as well replace hose while I'm at it.

Thanks,
ND

[fenixus]

in most cases the grommet (seal) is hardened and brittle and allows air to pass by, so needs replacing anyways at such mileage.

valve itself most often gets clogged inside (orifice) with carbon buildup or some burned oil and stops rattling when being shaken (mean it's bad).

the least probable is the hose getting clogged ... it ahs quite big diameter when compared to valve's orifice and I actually can't imagine hose getting clogged up before the valve does ... just my 2 cents.

also if any vacuum hoses are cracked on ends, then they are no good and call for replacement. same about glazed hardened hoses (can be brittle) being prone to micro-cracks, etc ...

do the cheap stuff before you touch the cat converter please, I would hate to see you paid hundreds to replace it with some questionable aftermarket part and on the end find everything same bad during emissions test ...

Originally Posted by nemodat

CTG: Very helpful, thanks. Two follow-up questions...

If gasket material falls through valve cover, any idea of the risk or severity of damage? At least one poster got away with it but perhaps he had a horseshoe

Second, the Toyota dealer garage said often the hoses connected to PCV get clogged and thay can often fix problem without even needing to replace PCV itself. Does that sound credible? Just wondering if I might as well replace hose while I'm at it.

Thanks,
ND

[CTG]

Oh, that reminds me- If you do have to replace the cat, make sure you use a premium one. DON'T CHEAP OUT! It'll cost you in the long run.
I used Magnaflow's premium line. More expensive? Yes indeed. Much more worth it though. Experience from the folks at the shop says the cheap ones can last as little as a year, where as they've put on premium ones 5+ years ago and still have no issue, and see the cars for their regular oil changes.
Spend a bit now, save down the road.

HOWEVER! If there is an issue beside the cat, replacing the cat may help you pass this year, but the other issue may burn out the new cat shortly there-after. Always make sure the other bases are covered first or you'll spend money twice.

[fenixus]

^right.

make sure car does NOT run RICH or burn oil, because if that is why the cat went bad, then the new one will kick the bucket in no time (much faster than the OEM one did).

[nemodat]

So I failed again this morning. Since my fail 3 days ago, I replaced the PCV valve (it was filthy), got an oil change and replaced the air filter.

Hopefully you can see table with various test results at the bottom (4 tests from April 09 to today). Perhaps that provides some useful information for diagnosis.

The good news is the HO went down from 0.8040 to 0.6164 (pass is .500), so I’m getting there. The bad news is the CO reading jumped from 6.5106 to 7.9154 in 3 days. That’s a jump of 1.4. If that jump repeats in the next text, I will fail the CO.

In terms of cost efficient next steps (no O2 sensors or cat), I am thinking replace spark plugs and get timing checked. Does that seem reasonable?

Any thoughts on why the CO reading jumped so much? Is this a bad sign?


Many thanks for any input.

ND

[nemodat]

Here's the test results, hopefully now legible.

Hydrocarbons Pass = 0.500
0.6877 (’09), 0.4633(’09), 0.8040 (’11), 0.6164 (’11)

Carbon Monoxide Pass = 9.32
9.0515 (’09), 5.5701 (’09), 6.5106 (’11), 7.9154 (’11)

Nitrogen Oxides Pass = 1.24
0.8606 (’09), 0.5941 (’09), 0.5135 (’11), 0.6097 (’11)

[fenixus]

well, excessive CO levels could be pointing to the failing cat converter ... but I'd rather expect ECU to detect P0420 first (low efficiency) ... so maybe you have some misbehaving sensors fooling ECU into preparing wrong air/fuel mixture?

It sounds likely after you only replaced PCV and that caused such drastic difference ...

I would look into testing o2/AFR sensors (how old time/mile-wise are they?), ECT sensor and MAP sensor (4 cylinder models use this one).

AFR sensors usually are useless after 150k miles.
o2 sensors are pretty much done around 100k miles.
replace them only with Denso or NGK and no other.

I've seen ECT sensors misreporting coolant temperatures to ECU at certain levels only while generally being good, at 125k miles

MAP sensors rarely go bad, but when they do so usually silently (one of primary feeds to ECU, so it doesn't know it's getting wrong data) and they can cause havoc.

check this article:
http://www.smogtips.com/failed-high-...onoxide-CO.cfm

also, usually when cat converter is real bad the car looses lots of power and have tendency of choking at higher RPM, does your experience any of those symptoms?