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Failing Smog: What To Do With All My Hydrocarbons
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Kburns737
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Joined: October 21, 2008
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Location: Ventura County
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PostPosted: Fri Aug 14, 2009 7:57 pm    Post subject: Failing Smog: What To Do With All My Hydrocarbons Reply with quote

Alright folks,
So I've got an 87 syncro here with the 2.1 in it. Been fiddling with it a few weeks now trying to get it to pass smog but my HC's are just too much. First time around it read out:

At Idle:
HC: 897
CO %: 1.12
CO2 % : 9.90
O2%: 5.76

At 2500 RPM:
HC: 978
CO %: 1.2
CO2 % : 12.30
O2%: 2.70

So I'd noticed it never seemed to be getting very warm, even zipping around lots of hills here in the tahoe/truckee area. So I replaced the thermostat( tested the new one too before installing it) and adjusted the TPS as well as I could. I also tried to lean out the AFM a hair, gave it a couple turns to the left, and I've got the original measurements written down still as well. Things seemed improved, brought my idle down to about 900 seemed a bit peppier on the hills and it got warmer going up them, not as much as I thought it should have, but enough to at least switch on the cooling fan. Much to my disappointment though, the results weren't much improved.

HC: 634
CO %: 0.42
CO2 % : 5.80
O2%: 12.40

At an idle, they didnt want to go through with it at 2500 since it was still so far off. I also took of the cat and examined it, everything looks very intact and pretty new, much nicer than some other cats I've had on older 1.9s
So anyone had any similar experiences, numbers like this? It seems to me that I need it to run a bit hotter, its way too rich, which for me explains why it runs so cool. I've run the oxygen sensor tests, everything seems fine. Tested the temp 2 sensor which also checks out. Right now I'm mostly just confused. The darn thing runs so well and even gets pretty good mpg, its got me baffled. Any help is much appreciated, all suggestions welcome.
Oh and I forgot to add this is for california smog laws and the max hc I believe is 150 at idle and 180 at 2500 rpm.


Kerry
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perrib
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PostPosted: Sat Aug 15, 2009 6:32 am    Post subject: Reply with quote

Ar you checking before or after the catalytic convertor. You may have an air leak, bad ignition wire, low compression,etc. Even without the catalytic convertor the HC should be under 200.
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madmax25
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PostPosted: Mon Aug 17, 2009 10:22 am    Post subject: Reply with quote

I went through the same thing a few months back, HC a few hundred above the limit. I forget now exactly what the problem was, but it was having problems with misfiring. The HC comes from unburned fuel. I'd make sure the timing is dead on (search for setting the total advance), and if the plugs/wires etc. could use replacing, might help. I was also dealing with a slightly broken ECU that made it idle really weird, which might have been it. I ended up borrowing a good one and it passed me. Also look for vacuum leaks and leaking around the air intakes/AFM. if it leaks there it could be leaning the mixture out and causing a misfire, making it really rich.
Can you hear any slight misfiring? Black tail pipe?
Also if you think it might be temp related, a new temp II sensor could help. I think they crap out quite often and really mess up the balance.
Good luck! Cool
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errolprowse
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PostPosted: Mon Aug 17, 2009 9:22 pm    Post subject: Reply with quote

my hc's were like that as well two months ago, found out it was a misfire. I changed the distributor/wires. fixed the misfire and hc went from 2000 to 27. oh and i also replaced the cat
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Kburns737
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PostPosted: Tue Aug 18, 2009 6:50 pm    Post subject: Reply with quote

The wires, cap and rotor are all new, I'm gonna order those ngk plugs. I was testing the lamba curve on the 02 sensor and I get readings all over the ballpark, from 10 to 1300 seems like maybe my 02 sensor might have crapped out, well I've got another one sitting around I can plug in and see. I've been worried about the timing, guess I'll have to break down and buy a light, mine is at home, since I'm only up here seasonally. Thanks for the hints, I'm in the backcountry 4 days a week, now I got three to fiddle around and somewhere to start at least.

Kerry
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wbx
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PostPosted: Wed Aug 19, 2009 1:35 am    Post subject: Reply with quote

Kburns737 wrote:
I was testing the lamba curve on the 02 sensor and I get readings all over the ballpark, from 10 to 1300 seems like maybe my 02 sensor might have crapped out, well I've got another one sitting around I can plug in and see.


That wild oscillation seems like a good thing, in my book. Narrow band O2 sensors used in our vans kind of act like an on-off switch telling the ECU "you are rich", "now you are lean", "oops, you are rich again" as the ECU corrects for the O2 sensor input. The O2 sensor can only tell rich or lean, not HOW rich or lean, so the best the ECU can do is oscillate around that stoichiometric tipping point.

But hey, you've got a spare sensor so sure... try it out!
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zerotofifty
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PostPosted: Wed Aug 19, 2009 7:59 am    Post subject: things to check Reply with quote

this smog results seems to indicate unburned gas and extra oxygen. If you were simply running rich, you will have excess HC but little oxygen as it would all be used up in burning the extra gas (unless you are running so rich that the engine cant fire, then you will have high HC AND high O2)

you might also have an air leak in teh exhaust system, that will give a high O2 reading. it may also effect the HC becuase the air leak will tell teh oxygen sensor that there is too much O2 in teh exhaust, teh engine will respond by enriching teh mixture up to the computers max limit of richness.

a shot catalyst will also make high HC levels, but your O2 level is still too high at 12 % even for a dead cat.

thus as suggested check your spark, amke sure you have good plugs and wires on all four. you can chek the spark plug one at a time by pulling them and cranking and look for a nice blue long spark. a mechanic with a scope can also check this

you also should inspect carfull the exhcuast for leaks. it seems that vanagons can get cracked exhaust manifolds , usually near teh sharp bends near the cylinder heads. mine had two cracks. they can be welded up, one was a bitch to get at int eh car but it did get fixed this way. you also may have leaks from loose exhaust bolts and gaskets)

if you O2 sensor is very old, that might be making the car run rich also, if the sensor is at the recommend service interval, I'd replace it. it can do wonders.


now if you have been running rich (or misfiring) for a while, your catalyst might be bad now, so that might need replacement, however I would not replace the catalyst first, without making sure your exhaust system is leak tight and ignition is right on. a new cataylst might clear this probelm up for smog testing, but if you dont get to the root cuase, your bandaiding something bad and your cat will soon die and your engine will suffer.

hope it is an easy fix for you.


also be sure you get the right vanagon three way catalyst. the vanagon uses a three way which is very nice. it cleans up HC, CO and NOx. cars with out the three way require an EGR valve to clean up the NOx, the vanagon uses the more better solution with the three way, no stinking egr valve to worry about!!!

at anyrate I'd look into an exhasut air leak that is giving false readings to teh O2 sensor, or bad spark/misfire from wires, dizzie or plugs. maybe your cat is going bad also. but youmust check out other things before the cat is replaced.
good luck
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Kburns737
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PostPosted: Wed Aug 19, 2009 11:50 am    Post subject: Reply with quote

Alright, well after fiddling a bit more I noticed my idle stabilizer doesnt seem to hum or buzz or vibrate like the book says it should. Would that mess with things in an major way? Also, idiot me, I just noticed that the tb switch was unplugged from me taking it out and fiddling with it, so that last smog check and result is probably pretty bogus, unfortunately the place I've been going to wont pretest it anymore, have to find somewhere else. And another idiot move, when i was checking my o2 sensors outputs, I had the multimeter on resistance not voltage so I've got to check that over again, sure was a long day was yesterday.

Kerry
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