KraZeeZX Posted November 4, 2004 Share Posted November 4, 2004 Went to get my Z inspected now that everythings been running fine for a while. I passed all the test with flying colors, but managed to fail the Nox test by a fairly wide margin. Crappy thing is... it could be one of a bunch of problems causing the failure. My Z has been running lean... no idea why, but it has been. I dont have EGR and I dont have a way to put it back on. I have my exhaust leak on my driver side header. And my coolant system has no thermostat right now.. so I'm probably running in open-loop all the time. I'm bringing my car to MTI (ls1 specialists) tomorrow to get a diagnostics scan to tell me what codes my engine has been throwing... hopefully that will shed some more light on the situation. Just a bummer since I was sure I'd get my sticker this time. -Vann Quote Link to comment Share on other sites More sharing options...
MYRON Posted November 4, 2004 Share Posted November 4, 2004 Vann, I have seen and heard of cars running fine and throwing NO code but the KNOX readings being way out of whack... Not that it would make a big difference in getting your sticker, but you may want to ask the station if his system is calibrated... also, Why dont you register your car in San Marcos (Hayes Co.)? I dont think you have to put it on the sniffer out here... If the system all checks out and there is nothing wrong with your car, send me a PM, I may be able to help you with your problem.. Myron Quote Link to comment Share on other sites More sharing options...
DaleMX Posted November 4, 2004 Share Posted November 4, 2004 Could just be the placement of the MAF. Might just need recalibrating. MTI will know. They have a great reputation. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 4, 2004 Share Posted November 4, 2004 Hmm... not a smog guru but I thought that one of the major benefits of EGR was to reduce NOx. Something about the combustion of the a/f mix with the exhaust gasses added wouldn't be as efficient. Efficiency makes NOx. Then again, I could be talking out my butt... Quote Link to comment Share on other sites More sharing options...
BrandonsZ Posted November 4, 2004 Share Posted November 4, 2004 the dang nox killed tow of my cars, I hat smog checking that's why I'm going all sub 1975. But the NOX is specifically heat related the chamber is too hot. What causes heat? High compression Lean condition Carbon build up Make your play I'm out!!! Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 5, 2004 Share Posted November 5, 2004 The EGR lowers combustion temps which reduces NOx emissions. Did you fail at all speeds, or just low speeds? When I fist bought my Z28 (LT1), I had it smogged and it failed NOx badly. The car had been sitting for months. I took the car for a hard burn down the freeway, dumped in a gallon of denatured alcohol and retested....passed with VERY low numbers..... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 5, 2004 Share Posted November 5, 2004 I did that the last time I smogged my Toyota truck, it had a very tired bottom end at the time and was burning lots of oil. Needless to say if you were within about 20 feet of the thing your eyes were burning due to the alcohol and I think I used a quart of alcohol with about 2 gallons of gas in the tank... but it passed! Quote Link to comment Share on other sites More sharing options...
KraZeeZX Posted November 5, 2004 Author Share Posted November 5, 2004 Ya.. I'm still not sure whether it's EGR related or not. Some other LS1'ers say the reason the newer LS1's dont have EGR is because they have a different cam to acoomodate the lack of EGR... so... EGR may be my problem. Too bad I dont have any way to put it back on my Z. The MAIN reason I didnt pass is because they are testing my Z based on the newer Corvette emissions! Now.. I know they are supposed to do the emissions test for the body style of the car, but they went ahead and typed up 5700 - 8cyl for the engine size for my test. I KNOW it would pass the 91 emissions, no problem... maybe I just need to bring it to another shop and take the Corvette fuel rail covers off. Myron - Well first, I know I'm throwing codes.. my ODB2 light shines nice and bright all the time, lol. I would get it done in San Marcos, but I really don't want to have my car up at school for any amount of time. Last time I had my Z at school with me it was broken into.. so, you know how that goes. Of course... if I can't pass here in Katy, then the 2 hour drive might be worth it. I'll let you know how the diagnostics go. DaleMX - ya.. MTI informed me that MAF placement and Catalytic converter placement might be off... I'm sure they can only help me out tomorrow. jmortensen - You're right.. EGR is specifically made to reduce Nox, but Ive been told that it won't reduce the numbers enough to get my car to pass... of course, MTI might be wrong, but we'll see. brandonengineer - lol.. ya, sucks to have a newer car with a swap. What sucks even more is that the shop was testing me based on even newer emissions tests. I'm sure the lean conditions are contributing to my failure... my A/F gauge NEVER comes close to reading rich and barely ever touches the stoic area. Tim240z - I failed at both speeds.. I was 200 over (950 over 750 standard)at high rpms and 400 over (1215 over 830 standard) at low rpms. My engine had been sitting for about 2 years... but Ive driven her for almost a month now and have rowed through all of the first 3 gears a few times. Would that still possibly be my problem? And what does the alcohol do for the testing? I dont burn any oil and the engine is responsive as hell...I'm just getting irritated because I can't figure out exactly what's causing my failure. Hopefully I dont have to reinstall EGR... I'll have to get new manifolds and I dont have any $$$ right now. -Vann Quote Link to comment Share on other sites More sharing options...
Tim240z Posted November 5, 2004 Share Posted November 5, 2004 The alcohol burns super clean, plus cleans stuff out. Try putting a 10% mix in the tank, running it hard (full redline shifts), then take it to the smog station and try again. Ask them to just do a check, not a test (do not report the results). If it looks good, run the full test.... Quote Link to comment Share on other sites More sharing options...
KraZeeZX Posted November 5, 2004 Author Share Posted November 5, 2004 The alcohol burns super clean' date=' plus cleans stuff out.Try putting a 10% mix in the tank, running it hard (full redline shifts), then take it to the smog station and try again. Ask them to just do a check, not a test (do not report the results). If it looks good, run the full test....[/quote'] Awesome!!... Funny cuz I just had another guy tell me the same thing and he passed off a huge cam in his LS1. I think I might definitely be doing this after I get my PCM codes checked out tomorrow. Another excuse to drive fast. -Vann Quote Link to comment Share on other sites More sharing options...
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