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josephf31 | High HC emissions -- redux | ||
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Hello all,
I know this has been touched on in past messages and I've searched but I'd like new and fresh opinions. My 'stock 91 L98 just failed NJ emissions for high HC; allowed is 220 I blew 491 on the idle test. CO is OK 1.20 allowed blew 0.88, CO2% 8.5, O2% 8.2 and the high idle test is OK, 220 HC allowed blew 58, CO 1.20 allowed blew 0.53, CO2% 10.7, O2% 5.4 Car was hot when tested, what I had to do so I did not fail for the check engine light was pull over about 1/2 mile before inspection, shut off engine, and disconnect battery for a minute to clear the light, then went to testing within 10-15 minutes -- this couldn't be the cause could it? I did the same thing 2 years ago... Only code is a 32 after extended highway driving which I've had for years, the car passed emissions with flying colors only 2 years ago and nothing has been changed except for maybe the evap canister and lines (had fuel tank replaced). Injectors were replaced probably 3-4 years ago with units rebuilt by FIC, along with many other items, plugs, wires, cap, rotor, EGR valve, etc. Car is driven under 5K a year. I've seen and heard many different things, what really works? Seafoam? if so how, exactly? Timing? if so, how, advancing a little beyond 6 BTC or wouldn't the ECM automatically compensate? Pulling a vacuum hose (wouldnt' this create a vacuum leak and increase HC?) This has been really frustrating, especially since it passed with the same setup...thanks all! |
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Posted on: 2013/6/9 19:31
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josephf31 | Re: High HC emissions -- redux | ||
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A little more info...after warmed up fully (surges when cold, been doing that for years) when idling in Drive there is an occasional slight mis...
Also what about CRC "Guaranteed To Pass"...? And, just noticed, it looks like NJ added an idle speed emissions test, the previous inspection did not show 2 tests, only one, at "2549 RPM", which would seem to me to be equivalent to the "new" "high idle" test...apparently they didn't check (low idle) speed emissions before? NJ stinks BTW LOL Thanks again all! |
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Posted on: 2013/6/9 20:16
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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Those are all loosely based on CA SMOG tests.
There is a dyno involved, and a low speed test and a marginally higher speed test. 15 and 25mph, IIRC... Now, there is one thing you are not talking about. The cats. Or, more than likely, the main cat. Is NJ doing a visual or just a sniff test? If it's just the sniff, I would replace the front y-pipe with one that has no cats, then, replace the single main cat with a new main cat. When you get that close with the numbers, the cat is more than likely dead or dying. Our Cherokee did that last year. It was in good tune, for sure, but it also wasn't passing. Threw on a new magnaflow cat and the numbers crashed down to earth. I mean CRASHED. I don't remember the specifics, but HC's went from failing at 500 or 600 to passing with under 50. If you have the $$, try to retrofit an LT1 style system. That would allow for dual cats and dual exhaust and will add about 30hp to the thing. If you buy a cat, get one that meets CA OBDII standards. They are more expensive, but they also last much much longer. |
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Posted on: 2013/6/9 21:20
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josephf31 | Re: High HC emissions -- redux | ||
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I *THINK* I may be found the problem; see picture, today I found the air intake bellows has 2 small holes in it right near the throttle body, one pretty good size you can see the white behind the openings.
Can someone confirm that this could very well be the cause of my high HC at idle emissions failure? Maybe even a occasional slight miss at idle? It would be the cause of a vacuum leak, correct? Hopefully it's something simple like this and not big $ like the cat. Thanks all! |
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Posted on: 2013/6/15 22:06
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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maybe... it won't hurt to fix it.
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Posted on: 2013/6/16 3:24
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screamin_conure | Re: High HC emissions -- redux | ||
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I'd be surprised that a leak in FRONT of the throttle body blades would cause high HC at idle, since theoretically the blades should be nearly sealed/closed at idle. A vacuum leak BEHIND the throttle body blades would be a different story. And I don't believe '91 had a mass airflow sensor either. But like Andy said, slap a bit of duct tape on those holes for a temporary fix and see if things change. |
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Posted on: 2013/6/17 21:29
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CentralCoaster | Re: High HC emissions -- redux | ||
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I would NEVER disconnect the battery before a smog test that included idle. Was your idle rock solid rpm? The smog tests here don't care what your average reading is during the test, it only takes one blip above the limit to fail you, so a solid idle is very important. Luckily they got rid of the idle test though.
Your idle CO, while passing, isn't ok either, it should be much lower. What is your code for? I've used that "guaranteed to pass" I guess it burns much more cleanly than normal gas. I have no idea what difference it made without doing back to back tests. I've used seafoam too. I will never again, as I don't feel comfortable risking hydrolock on my car. I probably hydrolocked my LTD with it awhile back and bent a rod, but it was junk anyways. That hole can't be helping, it's letting unmetered air into your car. Not a whole lot as there isn't much vacuum behind the filter though at idle. But idle is finicky so you want that maf getting everything. I'd fix that code properly, plug the hole, drive it a few trips to learn the idle, then run the car hard to redline on a few onramps, and smog it hot. My vette gets excellent mpg after a track day, so I reason that it will help the smog check too. |
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Posted on: 2013/6/18 19:34
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josephf31 | Re: High HC emissions -- redux | ||
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Quote:
Been getting a code 32 for (literally) a few years after any time at constant highway speeds for more than a little while. Code 32 is EGR, valve was replaced not long ago, no help, I tried replacing the EGR solenoid, no go. Somewhere I read that a problem with the evap control system could trigger a code 32 but I have not yet had time to track that down yet. Since a check engine light is an instant automatic fail, for the past 2 inspections (every other year here in NJ) I have pulled over a ways before the inspection station and briefly disconnected the battery since I always got a (code 32) check engine light on my drive there. It's passed the other times, though I believe that between this inspection (failed) and the last one 2 years ago when I passed, they now check emissions at idle instead of only at fast idle. Just got new bellows today hopefully this weekend will be nice I can do some more investigation and get this thing through emissions... |
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Posted on: 2013/6/18 23:56
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CentralCoaster | Re: High HC emissions -- redux | ||
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Hmm. I guess EGR should only affect Nox. But resetting the ECM will affect idle and everything else.
Does your EGR temp switch and circuit work? It should ground only when hot and EGR is flowing. It can throw a code if its shorted/grounded. Probably also if it doesn't ground out when it's supposed to be flowing, which sounds like your situation. The sole purpose of that switch is to throw codes. |
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Posted on: 2013/6/20 6:06
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josephf31 | Re: High HC emissions -- redux | ||
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I though EGR would only impact NOx too, that's what my research shows. Not sure if the solenoid works, it's a part that's no longer available. Also not sure how to test it but if it's in the Helm's I'll look it up... |
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Posted on: 2013/6/21 0:28
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Scott7 | Re: High HC emissions -- redux | ||
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I agree with Andy on this, take a close look at your cat. I've had the pleasure of replacing that single cat multiple times to pass Colorado's sniffing tests. Recently I converted the system to two individual small cats, no y-pipes, and have had no problems since. I'm on my 4th year with this set-up, yesterday I went through emissions testing and passed with flying colors, examples: HC GPM reading O.6832 (Limit 2.0000), CO GMP reading 4.9566 (Limit 20.0000), NOx GPM reading 1.0589 (Limit 4.0000). |
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Posted on: 2013/6/21 19:05
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josephf31 | Re: High HC emissions -- redux | ||
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I'm guessing I still have the OEM cat(s) on the car, and it's got a little over 100K miles.
What is the "normal" life expectancy of a factory cat? Is there any way to do any actual testing of the cat? Thanks everyone! |
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Posted on: 2013/6/21 19:41
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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there is no "test" for the cat... but after 100k miles and 20 years, I am betting it's toast. In those days, they only had to be warranted for some 50k miles, IIRC. OBDI days were so innocent.
If you have to replace, I would go with a true dual system anyway... the average NJ smog tech won't know, and the end result will add 30hp. If you can find a used LT1 exhaust, that's your best bet. Check with Contemporary Corvette in Reading, PA, for a price. Also scour craigslist and ebay. You should pay no more than $150 for a full LT1 OEM catback, with hangers. If you could wait until Carlisle... I am sure you could get one for nearly free from Corsa, but you will need the hangers. the pricy part will be the cats... I would get the Magnaflow cats for a 92 vette, pre-welded for the LT1. Should work just fine. |
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Posted on: 2013/6/21 23:56
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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josephf31 | Re: High HC emissions -- redux | ||
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I'd love to replace the whole system right now but can't afford it...
If I replace ONLY the main cat, should that be enough to clean up the emissions issue? I can get a Magnaflow cat for about $140 from Summit Racing. |
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Posted on: 2013/6/25 15:53
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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that should do it.
The main cats just don't hold up. You are in NJ, they mandate the "CA standard" cat. If so, don't complain about the cost, it's a much better can than the basic replacement. It will last a long time... it has to meet OBDII durability standards. It might be more expensive, but it will 3 or 4 times longer. |
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Posted on: 2013/6/25 16:16
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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josephf31 | Re: High HC emissions -- redux | ||
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Maybe it's just me :-) but I'm confused http://shop.advanceautoparts.com/weba ... teel-magnaflow_22317388-p Says only not for sale in CA, nothing about NJ. Most other sites list this and other cats (e.g. Catco) as being "49 state legal". Is this cat not legal in NJ? or is it just not as good? One more ? do I need to worry about the pre-cats or if I replace only the main should that do the (emissions) trick? Thanks all! |
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Posted on: 2013/6/25 16:31
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screamin_conure | Re: High HC emissions -- redux | ||
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It's legal in NJ: http://www.magnaflow.com/02catalytic_ ... ogid=2918&directfit=93441 I've actually running the LT1 versions of these same cats on my '92 for the last two years. I passed Indiana's sniff test with flying colors. With the stock exhaust, they added a little bit of bass tone too. |
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Posted on: 2013/6/25 17:26
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screamin_conure | Re: High HC emissions -- redux | ||
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I guess that's up to you. If you're looking to do the bare minimum to get your car to pass, try replacing just the main cat. If you're looking to replace/update all of the old emissions-related exhaust components, replace them all. When I discovered that the passenger side cat on my car had started to deteriorate, I bit the bullet and went ahead and replaced them both. I figured it was likely just a matter of time before the driver's side started to go. In my last post, I meant to say if the product description states "49-state", it's legal for sale/use in any state outside of California, including New Jersey. |
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Posted on: 2013/6/25 17:35
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Scott7 | Re: High HC emissions -- redux | ||
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Another that you might want to look at is Random Technology. They offer a pretty nice product that performs well. When I did the change over on my car and went to a dual exhaust system I used their small bullet cats and they've held up well. Just a thought for you . |
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Posted on: 2013/6/25 17:42
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josephf31 | Re: High HC emissions -- redux | ||
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I saw the Random Tech units, they look nice, but pricey...I'm not loaded like you guys LOL
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Posted on: 2013/6/25 21:54
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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Trust me, I ain't loaded... just not afraid to spend some money for quality.
Don't get me wrong, the Magnaflow cat is a good as they get. Very good part. |
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Posted on: 2013/6/26 4:21
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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Scott7 | Re: High HC emissions -- redux | ||
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Ya, and wouldn't that be nice.
There's lots of good solutions and generally money for quality is money well spent, but sometimes . |
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Posted on: 2013/6/26 18:00
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josephf31 | Re: High HC emissions -- redux | ||
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Well my new Magnaflow converter arrived this week, hopefully this weekend I'll be able to install it. I've already replaced the O2 sensor, cleaned the air filter, changed the oil and filter; I'll check the timing then cross my fingers and bring her back to the testing facility soon, thanks all for your help.
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Posted on: 2013/7/11 13:58
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Scott7 | Re: High HC emissions -- redux | ||
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You get to do all the work so have a good time with your car this weekend I'm sure everything will work out well for you and the sniffer approves. That'll be cool
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Posted on: 2013/7/12 23:09
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josephf31 | Re: High HC emissions -- redux | ||
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Well check this out, I don't think the cat does a very good job when there is nothing inside it eh? LOL Wow I've never seen this before. Ya think this could be why I failed emissions? :-)
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Posted on: 2013/7/15 2:34
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Matatk | Re: High HC emissions -- redux | ||
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Not uncommon...check your mufflers and the exhaust for the broken pieces that could affect the exhaust flow.
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Posted on: 2013/7/15 2:37
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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Scott7 | Re: High HC emissions -- redux | ||
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Whoa, as Matt says you best be checking. . .
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Posted on: 2013/7/15 19:10
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josephf31 | Re: High HC emissions -- redux | ||
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Well, here is the latest, but NOT the greatest;
Brought the car back to NJ inspection yesterday, and failed (again) but this time for high HC at high idle; reversed results of the first fail. Here is a recap; First fail; @idle HC 491 allowed 220 (FAIL) CO 0.88 allowed 1.20 CO2 8.5 O2 8.2 @high idle HC 58 allowed 220 CO 0.53 allowed 1.20 CO2 10.7 O2 5.4 Second fail; @idle HC 199 allowed 220 CO 0.56 allowed 1.20 CO2 14.0 O2 1.1 @high idle HC 446 allowed 220 (FAIL) CO 0.71 allowed 1.20 CO2 14.5 O2 0.4 I don't get it, and I'm ready to throw in the towel and bring it to my mechanic. Changes between tests: New Magnaflow catalytic converter -- also fixed exhaust leak and replaced air pump hose New O2 sensor New air intake bellows Change oil and filter Clean air filter Clean injectors Check timing (was at 7, spec is 6) Observations; I have had an Accel foam filter for years, it passed with this filter before, I cleaned it but did not re-oil it so it is almost dry. I was getting a code 32 for (literally) years, now I don't get it any longer so there is no need to pull over before the inspection and disconnect the battery briefly to clear the check engine light. There is a very slight miss at idle which I can't trace down, it's been there for quite some time not sure it has anything to do with the numbers. So, what in the heck caused the changes in numbers, and most specifically, the "new" fail, HC at high idle? I am baffled. Any help is appreciated....thanks all. |
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Posted on: 2013/7/28 21:46
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screamin_conure | Re: High HC emissions -- redux | ||
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Couple of questions...
Did you replace just the main cat, or the pre-cats too? What kind of shape are your plugs? How fresh is the gas in your tank? |
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Posted on: 2013/7/29 20:46
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josephf31 | Re: High HC emissions -- redux | ||
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Just the main cat; don't have the time, money or facilities to replace the precats too Have not checked the plugs but they have less than 5K miles on them Gas is recently filled |
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Posted on: 2013/7/29 21:01
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screamin_conure | Re: High HC emissions -- redux | ||
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I think it still might be worth pulling a few plugs and checking them. Even with only 5k on them, given the condition of your main cat, and the fact that your HCs are still high (though passing at low idle), I'm betting that you've been blowing high HCs for a while now and your plugs may be pre-maturely toasted. I really think you're dealing with a lack of proper combustion (i.e., poor ignition). High HC pretty much means unburned fuel is making it through the entire exhaust system. I don't think there's anything that will destroy a cat like yours was faster than high levels of HC.
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Posted on: 2013/7/29 21:57
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Matatk | Re: High HC emissions -- redux | ||
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They make a fuel additive that is supposed to help you pass emissions....wonder if that would help?
I read somewhere that the CTS being out of whack can affect the emissions because it adds fuel. Can you ohm or scan that and check if it's in spec? Did you check for exhaust leaks, I'm sorry I don't remember from earlier in the thread. |
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Posted on: 2013/7/29 22:03
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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Matatk | Re: High HC emissions -- redux | ||
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Also, since ignition problems can cause unburnt fuel problems, have you ever changed the cap and rotor or plug wires?
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Posted on: 2013/7/29 22:06
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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josephf31 | Re: High HC emissions -- redux | ||
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Cap rotor and plug wires are all less than 5K old. Had an exhaust leak (at back of cat) fixed it when cat replaced. Tried the "guaranteed to pass" stuff before all it is is injector cleaner. I did put a can of Seafoam in the fuel tank and a bottle of Heet figured it couldn't hurt. CTS? |
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Posted on: 2013/7/29 23:47
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Matatk | Re: High HC emissions -- redux | ||
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Cts= coolant temperature sensor on the front of the intake manifold.
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Posted on: 2013/7/30 2:19
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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Matatk | Re: High HC emissions -- redux | ||
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Is the car running in closed loop? Do you have headers?
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Posted on: 2013/7/30 3:37
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josephf31 | Re: High HC emissions -- redux | ||
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No headers, stock manifolds. Pretty sure it's not in loop how can I tell for sure? |
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Posted on: 2013/7/30 21:38
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screamin_conure | Re: High HC emissions -- redux | ||
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The only way to tell if you're going into closed loop is with an OBD1 scan tool. Something like this: http://www.autoxray.com/product_detail.php?pid=94. Prices for these can vary, and you can find good deals for used ones on eBay. If you do pick one up, since your car is a '91, make sure that it is for OBD1, and that it can read live ECM data. Otherwise, just about every well equipped repair shop / mechanic will have a scope or scan tool that can tell what's going on with your system as well. Ron |
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Posted on: 2013/7/31 17:21
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Matatk | Re: High HC emissions -- redux | ||
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You can use a paperclip and observe the check engine light on the dash. Instructions are here: http://forums.corvetteforum.com/c4-te ... cation-91-5-7l-vette.html It also references the IAT causing running problems. I recommend getting the car scanned with a tech 1, laptop with tuning software, or equivalent scanner so you can see what your sensors are doing. |
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Posted on: 2013/8/1 1:29
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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screamin_conure | Re: High HC emissions -- redux | ||
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You learn something new every day! I had NO CLUE you could check for open/closed loop operation with a paperclip! Very cool Matt! |
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Posted on: 2013/8/1 17:35
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josephf31 | Re: High HC emissions -- redux | ||
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Have had to put this project on hold recently due to other issues, but ready to get back to it now...
Question; if the pre-cats are shot wouldn't that cause my high HC emissions? The idle HC dropped a lot when I replaced the main cat, figuring if the main one was that bad (totally blown out) the pre-cats may not be so hot... If that is the case, would replacing the pipes without pre-cats and leaving just the main cat cause trouble passing the NJ emissions? |
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Posted on: 2013/9/17 5:42
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bogus | Re: High HC emissions -- redux | ||
Grand Imperial Pooh-Bah
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The precats did 90% of their work at start-up.
If the engine is at op temp, they are done. This is why ditching them is such a good idea. As for NJ? should pass the sniff... again, once warmed up, but the visual is suspect.... I donno how anal they are. This is when I recommend an LT1 style dual cat swap. |
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Posted on: 2013/9/17 15:48
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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