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Thread: 1989 SC Failed CA SMOG Emissions Help(passed 2-12-14 update)

  1. #1
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    1989 SC Failed CA SMOG Emissions Help(passed 2-12-14 update)

    So, I took my 1989 sc 5 speed in for smog. It failed emissions.

    I had fuel system cleaner in the gas, which probably didn't help. Also there was most likely some very old gas mixed in with the fresh gas.

    Here's the read out @ 15.6mph target 15.0mph. Load hp 16.9 target 17.1

    HC:
    135 ppm actual, Max Allowed 106 ppm

    NO(x):
    1674 ppm actual, Max Allowed 762 ppm

    CO:
    .53% actual, Max .70%

    CO2:
    14.2%

    O2:
    .4%

    P.E.F.:
    .471

    This car has been sitting for many years. I have put 13 gallons of fresh 91 octane gas in it and have driven it around for awhile to try to get the old gas out of it.

    Typically high HC from my experience is a result of poor or failing catalytic converters. And nox is usually something to do with the egr system.

    The car runs and drives good. I just changed the oil/filter, & fuel filter. There are no disconnected vacuum lines. I will be checking for leaks, or incorrectly routed lines.

    The HC numbers are pretty close. Do you guys think this is something where if I give her a full tune up(plugs, wires, o2 sensors, fpr etc) it will pass? Or are the #'s too far off & I need new cats.

    Update 1-20-14:
    Since failing smog I have replaced with new parts Bosch o2 sensors, autolite double platinum plugs gapped @ .047", duralast plug wires all tested under 5k ohms resistance, & tested the egr valve at idle. The car dies as soon as I apply vacuum to the egr valve.

    Update 1-23-14
    Took it in for smog again. This time it passed everything except NO(x). I found that the egr vacuum solenoid was frozen and not allowing the egr to work. I'm hoping this will be enough for it to pass.

    Update 1-31-14
    Today I replaced the egr valve. Recently replaced the egr vacuum solenoid. The hose that connects between the egr tube & pfe sensor was broke off. This caused not only an exhaust leak before the o2 sensor, but also insufficient flow to the egr system. I replaced the pfe hose with a new high temp silicone hose as well. This took care of the code 33. Hoping this is all what caused such high nox.

    Update 2-4-14
    Took it in for smog again today. Same as last time, everything passed except nox. Even with a nearly completely new egr system the nox still failed.

    Update 2-10-14
    New Catalytic Converter Direct Fit Pipe arrived today:
    Looks to be well made, and better flow than oem for sure. The resonator is wide and open inside. 5yr/50,000 mile warranty

    Inside the resonator


    Update 2-12-14
    Passed smog today. The HC numbers were 0ppm @ idle, & 3ppm @2500rpm. The two stage idle test that the car actually needed didn't even screen for nox emissions, so I don't know if those were reduced at all, but considering the HC emissions pretty much disappeared completely I would venture to say the oem cats were either clogged, or bad. Either way the car runs a lot better with this new mid pipe in place. Definitely more power and running a lot more smooth.

    Thank You all for your help and advice along the way I appreciate it very much.
    Last edited by Xounlistedxox; 02-12-2014 at 06:38 PM. Reason: Updating info

  2. #2
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    If it still has cats, temp gun them and the pipes to see if they're flowing or not...or just grab hold and pray

    New air filter and clean the MAF wires.

  3. #3
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    Quote Originally Posted by KMT View Post
    If it still has cats, temp gun them and the pipes to see if they're flowing or not...or just grab hold and pray

    New air filter and clean the MAF wires.
    Will do. How do I know they're flowing? Any idea of temperature ranges that are acceptable?

  4. #4
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    Quote Originally Posted by Xounlistedxox View Post
    Will do. How do I know they're flowing? Any idea of temperature ranges that are acceptable?
    If the pipe right after the cat is measurably cooler, the cat is suspected plugged and overheating. If flow is decent, the cat won't be that much hotter than the pipes before and after. If the cats glowing after a spirited run, that's not good

    Any foul smell out the exhaust?

    If you end up replacing them, look into hi-flow cats and downpipes, at the least. My '90 exhibited near identical stats from one smog test to the next (passing both easily) after I had them installed.

    My brother just failed in is '90 964, and after a new battery, all was good, so you never know what's going to make the machines happy.
    Last edited by KMT; 01-13-2014 at 04:41 PM.

  5. #5
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    Does anyone here have experience will pulling the spout connecter? It seems to be a common cure on the SHO forums, as it tells the computer to go to default timing of 10 degrees and supposedly does work for a lot of folks to get by. Not sure what the effects on the SC are.

    I've always heard get the cats good and hot, so go out and drive hard, but am no expert. I had a bit of trouble getting my 90 SHO to pass after sitting for almost a year.

  6. #6
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    Quote Originally Posted by KMT View Post
    If the pipe right after the cat is measurably cooler, the cat is suspected plugged and overheating. If flow is decent, the cat won't be that much hotter than the pipes before and after. If the cats glowing after a spirited run, that's not good

    Any foul smell out the exhaust?

    If you end up replacing them, look into hi-flow cats and downpipes, at the least. My '90 exhibited near identical stats from one smog test to the next (passing both easily) after I had them installed.

    My brother just failed in is '90 964, and after a new battery, all was good, so you never know what's going to make the machines happy.
    Looks like the driver side might be ok all temps on and sround it erre 200 or less. passenger side was 300 on the body and under 200 before & after

  7. #7
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    Huh...50% higher... It's a bit further back as I recall and the exhaust flow on that side isn't quite as good as on the left, but that still seems odd, I think.

    Sorry if I missed it - looked at the plugs yet?

  8. #8
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    Nox is whats killing you. Does your model have an egr?. It may benefit from a clean out...maybe the guy skipped the functional test. 2nd Is your vac / boost gauge showing close to 20 and steady at idle? just for a clean bill of health. If you rule that out you probably have contaminated cats... Do you know if it had a recent head gasket failure? coolant kills cats and o2 sensors. Don't forget you'll need "CARB approved" Cats...not the exact identical ones the other 49 states use just without the ID tag I've also heard good things disconnecting the spout as mentioned above. Good luck. I know it's frustrating.
    Last edited by figulaz; 01-13-2014 at 09:51 PM.

  9. #9
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    Quote Originally Posted by figulaz View Post
    Nox is whats killing you. Does your model have an egr?. It may benefit from a clean out...maybe the guy skipped the functional test. 2nd Is your vac / boost gauge showing close to 20 and steady at idle? just for a clean bill of health. If you rule that out you probably have contaminated cats... Do you know if it had a recent head gasket failure? coolant kills cats and o2 sensors. Don't forget you'll need "CARB approved" Cats...not the exact identical ones the other 49 states use just without the ID tag I've also heard good things disconnecting the spout as mentioned above. Good luck. I know it's frustrating.
    Yes it does have an egr, I'll be looking into that soon. It idles with a steady near 20 on the vacuum side. No work has been done on this car for years. It has been sitting for the most part.

    I did find this today too. Can't be good. This was on the passenger side which was the side with the catalytic converter that was much hotter than the other. Also I pulled off the mid pipe today. The passenger side cat appeared to be in shape. No damage, or odd color. No odd smells. The driver side cat is strangely shaped, so I couldn't get a look at the cat material even with a telescoping mirror. There was no material rattling around in the pipe. No cat material in the resonator either. I'm crossing my fingers that this broken sensor was most likely causing a lean condition which resulted in high nox & HC.


  10. #10
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    You're going to replace both O2 sensors, I presume

  11. #11
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    yeah. change out your O2 sensors with new. disconnect battery and then drive it around so the computer gets used to it...new fuel tables...I think they're about $40-$45 each. change out the spark plugs too. If it's your first time changing these in a SC you're in for a fun filled afternoon. If you have a hand vac pump you can test the egr....just activate the diaphram by pumping it at idle and the engine should stall out. you can also connect direct vacuum from the engine if you don't have pump. You don't want to remove the egr if you don't have to. They're hard to get to and the manifold pipe is usually rusted frozen.

  12. #12
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    Quote Originally Posted by KMT View Post
    You're going to replace both O2 sensors, I presume
    I had some known good o2 sensors from my mustang laying around & they're the same part # as the sc replacement. I put them in last night, then on the way home a CEL came on while driving. I'll have to pull the codes today to see what they are. It'll be strange if that broken o2 sensor never threw a code, but o2's in good shape do.

  13. #13
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    That broken sensor could have been masking an issue - maybe the issue that led to the song test fail.

    What do the plugs look like?

  14. #14
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    Quote Originally Posted by figulaz View Post
    yeah. change out your O2 sensors with new. disconnect battery and then drive it around so the computer gets used to it...new fuel tables...I think they're about $40-$45 each. change out the spark plugs too. If it's your first time changing these in a SC you're in for a fun filled afternoon. If you have a hand vac pump you can test the egr....just activate the diaphram by pumping it at idle and the engine should stall out. you can also connect direct vacuum from the engine if you don't have pump. You don't want to remove the egr if you don't have to. They're hard to get to and the manifold pipe is usually rusted frozen.
    Yeah, while I had the mid part of the exhaust out it looked like it would actually be easier to change the plugs from the bottom. Either way it doesn't look like much fun at all.

    I have a hand vacuum pump, so I can test the egr, it definitely doesn't look like any fun to remove/replace either.

    All of the exhaust bolts were completely frozen. Took about 2 hours to get the mid pipe off without breaking any bolts. Lots of penetrating oil & patience. Wound up not breaking any bolts, or even messing up any threads. Put plenty of anti seize on all threads before reassembly

  15. #15
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    Im also getting an egr cel code 33. Is this usually the valve itself?

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