Shoot, I failed Smog: HC's too high

[Heat Racer]

So my '98 RS (over 150k miles on it)failed smog today. The HC level was too high at idle. The smog guy said it's probably the O2 sensors or cats. Does anyone have any ideas how to narrow down if it's the sensors or the cats, so I don't go throwing parts all willy-nilly at the problem? If it is the cats, is there any way to tell if it's only one that needs to be replaced? I'm shocked at how expensive cats for the Impreza are. I got a universal high-flow Magnaflow one for my Datsun for $83

[tweak]

is your CEL on if it is get it on a code reader to see if its throwing a o2 code replace of needed

[Heat Racer]

No, there's no CEL. Can an O2 sensor be off enough that it would fail emissions, but not set off a CEL? Or does that pretty much confirm it's the catalytic converters?

[tweak]

it vary well may be one of the o2s starting to go bad. on the plus side they are not that expensive and are easily done. but if your like me and dont have the money to throw at it then more thought and research is needed to figure out the exact problem. it could be time for them to be replaced anyway just bad enough to throw everything off. all else fails you may end up with new cats and o2s when your done and one less thing to worry about next year.

[Daddy_Digital]

if your not getting a CEL code for the o2 sensors...its obvious that it ay very well be your catalytic converter thats bad. replacing o2 sensors and a cat isnt cheap. if all else fails, put some alcohol in the gas tank and it should get u to pass. i did this before and it worked and it didnt do anything to my car. good luck.

[winski357]

yay for michigan not having SMOG!!! :D :D :D

lol sorry

[kurt.]

How much did you fail by? Usually the cat will last until about 220k miles, so I'd be surprised if it was that at the mileage you stated, but it's still possible. There should be a spec in the FSM for the resistance in the O2 and how to check it. I would start there and if all seems fine, replace the cat. One thing is that a lot of the aftermarket cats will still fail the NOx test or at least that's my experience in Cali.
Do you know of anyone else local to you to maybe borrow some parts to swap in place and retest to define the problem? The cat and the O2 are both easy to replace with basic hand tools.

-Kurt

[LPPrelude]

if your not getting a CEL code for the o2 sensors...its obvious that it ay very well be your catalytic converter thats bad. replacing o2 sensors and a cat isnt cheap. if all else fails, put some alcohol in the gas tank and it should get u to pass. i did this before and it worked and it didnt do anything to my car. good luck.

Fill up the tank and use about 1 gallon of E85.
Or pour some denatured alcohol in the tank.
Just be careful not to over do it.

But it doesn depend how high the HC numbers were.
Using a gallon of E85 in the tank can drop the HC number by up to about 20% but if you are WAY HIGH then there is a real issue going on.

[Heat Racer]

From what I recall, at idle, the HC's were 157, while the max allowed was like 100.

Where do I get E85? Wasn't there something about it that's corrosive to fuel lines or something?

Haha, man, my cats and O2 sensors are probably so caked with dried mud that they'll be quite a mess to get off! :D

[alosix]

There's a station right outside of the Costco in redwood city that had E85. They seemed to specialize in all things bio.

I'd think if your cat were dead you'd be seeing high NOx as well.

I think we need a DI Peninsula community smog cat :)...

Do you have a code reader that can pull your fuel trims? It would be interesting to see what the ECU was doing there.

You only failed at idle right? not the 2500rpm?

Jason

[Heat Racer]

Ok, so I'm looking at my smog report card now.. At idle, the HC was 157 (out of 100 max). At 2500rpm, the HC was 22 (out of 130 max). So that's really strange why it's so high at idle but not at speed! If the cats were bad, wouldn't the HC be high at 2500rpms too? Hmm, I don't see anything about a Nox measurement..

I have a Scangauge II, but I don't know what measurement I'd be looking for in order to diagnose it any further..

Lol, I like the idea of a community smog cat! ;)

[vettetech249]

Check that your egr is working and not stuck

[Heat Racer]

Check that your egr is working and not stuck

I just took the car to the dealer today and had them inspect the EGR, and they said it was working ok. Any other devices or sensors that could affect the HC's at idle?

[alexkauer]

[QUOTE=Heat Racer;300610]I just took the car to the dealer today and had them inspect the EGR, and they said it was working ok. Any other devices or sensors that could affect the HC's at idle?[/QUOTE
Been chasing around my check engine light also, Check your bypass transducer or the electro-mechanical valve that controls the egr...check this article...it also has a couple othere things that cause a P0400 code...http://www.subaruoutback.org/forums/66-problems-maintenance/13984-p0400-trouble-code-cel-egr.html

[AWDmaster]

Ok, so I'm looking at my smog report card now.. At idle, the HC was 157 (out of 100 max). At 2500rpm, the HC was 22 (out of 130 max). So that's really strange why it's so high at idle but not at speed! If the cats were bad, wouldn't the HC be high at 2500rpms too?

The hotter the cats are, the more efficient they are...

I would try this... New plugs, and gap them slightly more than recommended. Change your oil RIGHT before going in for the smog. Run the car around and get it nice and hot and get it in for the smog as soon as possible... like I said the hotter the cats, the more efficient they are. If the cats have time to cool down, the more likely it is you will fail. Also, goto any Autozone or O'Reilly Auto and get this stuff (can't remember what its called right now) you put it in your gas tank and it is supposed to clean up the tail-pipe emissions.

I had a REALLY hard time passing smog with my '97 Brighton... First thing I did was buy a new cat section and o2 sensors and it still failed. So I did what I recommended above, and passed just fine! Hope this helps you.

[Heat Racer]

So I changed my O2 sensors and took it back for a retest.. I failed even worse than before!! Once again, it's the HC (hydrocarbons) again, through the roof, but only at idle. It's at double the maximum allowed! So tricks like having the cats be a little hotter won't be enough to wing my way through when it's off by that much..

It was explained to me that the the HC's are basically unburned fuel, which should mean that too much fuel is being dumped in at idle. And if timing is all computer-controlled, I'm trying to think what could cause too much fuel to be dumped in at idle, but not at higher rpm.. Fuel pressure regulator maybe? What else, you think?

[alosix]

Hmm, now that's interesting. Unsure if my tactrix cable would read anything useful out of a 98.

To me, unless you have an injector that's really hosed up.. like stuck open hosed up, I really can't see the fuel system being an issue @ idle to make it run rich.

A few things that I think might make it run rich:

1.) IAC stuck closed a bit. Not really sure you'd notice it all that much given the bay area temps.

2.) Evap solenoid stuck open/sucking fuel somehow.

I wouldn't doubt that new O2s would make it worse.

Should be able to see your AFR @ idle with most code readers, if you can't with yours you can steal mine for a few.

Jason

[kurt.]

If the cats are not to temp, you can fail miserably. How.much did you drive it before testing and how long did it sit before actually being tested? If a car is on the edge of not passing, I usually give ot an Italian tune up by driving it around at ~4k for 20 minutes and then leave it running and revving it.once in awhile while its waiting to go on the.machine.
Heat is the additive a lot.of people dump in the tank. The other.thing you can do is add an.alcohol based fuel to your tank which will make it run leaner..

-Kurt

[LPPrelude]

Find a mid section from someone else to try out. Basically cats that aren't 150k miles old.

Leakdown test that motor too.
You can be pulling in some coolant slowly and causing it to fail.

[xbmxxx]

the autozone additive is called Guaranteed To Pass, when I worked there I had a lot of people tell me it worked.

[Heat Racer]

the autozone additive is called Guaranteed To Pass, when I worked there I had a lot of people tell me it worked.

I'd already put that in on my last attempt, and I had driven more than enough to heat the cats up. These are all things that might lower the smog output a little, but when it's failing by more than double the maximum, there's something really wrong..

So I was thinking a bit more about that the elevated HC's mean... As unburned fuel, I originally thought too much fuel was being dumped in, but the key word is "unburned".. So maybe it's not that too much fuel is being put in, but perhaps something is keeping it from getting ignited at idle.. I'll check the sparkplugs (NGK Iridiums, which were fine when I checked em last year), but I would think it would cause a lot of other noticeable problems if they were failing to ignite the fuel that badly. What other problems/parts could cause failure to ignite the fuel but only at idle?

[alosix]

my gut kinda says iridiums might be a bit much for a stock NA car.

Have you checked the gap on them lately? Seems the part number is pretty close between the RS version and the WRX version, but the WRX has about 1/2 the gap.

I'd probably throw a cheap set of coppers in there.

You having any alternator or charging problems BTW? kinda wondering if the spark just isn't hot enough at idle.

[Heat Racer]

my gut kinda says iridiums might be a bit much for a stock NA car.

Have you checked the gap on them lately? Seems the part number is pretty close between the RS version and the WRX version, but the WRX has about 1/2 the gap.

I'd probably throw a cheap set of coppers in there.

You having any alternator or charging problems BTW? kinda wondering if the spark just isn't hot enough at idle.

I'll check the gap this weekend.. What should it be? Oh, and the sparkplug wires are NGK wires that're only a year old.

The car does seem to take more cranks to fire up than my other cars, but I dunno if that'd be related. Other than that, I do have a digital voltmeter on the car and it seems the charging system is operating normally.

[Heat Racer]

Ok, so I replaced the sparkplugs and put the stock air intake back on and still failed, so I eliminated those as factors. When I pulled the old sparkplugs, I found that one of them was damp and smelled like gasoline (even though the car hadn't been started in a couple weeks)... Would this mean the injector is leaking/messed up?

[Heat Racer]

Whoo-hoo! After over 5 months of failing smog, trying to figure it out, and throwing parts at it, my Subaru finally passed smog! =D I replaced the front catalytic converter, and the HC's went from '200' down to '11'. An expensive fix, but just glad to have it working and over with!