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Thread: 93 LT1 emissions problems
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10-09-2015, 12:59 PM #1Lurker
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- JOE MACDONALD
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- 1993 PONTIAC FIREBIRD FORMULA
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93 LT1 emissions problems
Hey everyone, Ive been having some serious issues trying to get my car through Delaware emissions and was hoping someone could shed some light on my problem. The car is a 93 formula firebird, stock lt1 with long tube headers and still has a cat on it as well. I recently did a tune up on the car after it initially failed emissions twice in stock form before the headers were put on. Amazingly enough the car had the original opti on it right down to the cap from 93 and was still running quite well, however it was failing hydrocarbons by 234ppm, the limit in DE is 220ppm and CO's are 1.20ppm. So I replaced all the ignition components, opti, wires, plugs, coil and icm as well as waterpump, thermostat, coolant temp sensor, new heated o2's and also a egr delete since the headers did not have a provision for it. I just put brand new 22lb injectors and a fpr on the car at the recommendation of a local shop which did help the car some however now the car is failing worse with hydrocarbons now at 705ppm and CO's at 1.31ppm. This is also only happening on the idle test, the car passes the the high idle test with flying colors. I have searched the forum till my eyes hurt reading posts of other members cars that had similar problems and now at a loss at what to do. Any help or advice is greatly appreciated, thanks in advance.
93 FORMULA FIREBIRD, black hardtop, auto, long tubes, ory, ls1 lid,
97 CAMARO SS SLP, black hardtop 6 speed, shorty headers
84 MONTE CARLO SS, 305HO, th400, 3.42's
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10-09-2015, 09:54 PM #2"The Rock"
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Talk to our tunning guys. They may be able to tell u what to look for in a data log and what to adjust in the tune to clean it up.
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10-09-2015, 10:54 PM #3Lurker
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- JOE MACDONALD
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- 1993 PONTIAC FIREBIRD FORMULA
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- HARRINGTON, DELAWARE
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I'll give them a shout , thanks man
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The Following User Says Thank You to 84MONTESS For This Post:
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10-11-2015, 03:35 AM #4
It failed twice in STOCK form, so you put long tube headers and on ORY with a cat some where in the exhaust? Your cat is most likely too far back in the pipe to get enough heat to do its job at idle. You have a leak in your exhaust upstream of the O2 sensors. Then you threw a bunch of parts at it hoping to get it to pass.
Not trying to be a dick, Look at my sig. I have a FULL emissions 93 in CA and my last smog test my HC at idle were 37 and 11 at 2500 rpm.
A little more info on your car would be helpful. New cat, in the stock location? Or is it way back in the merge of the ORY?93 LT1 M6, LE, 223/230 .565/.565 112, Stg2 heads, Ported intake, 32lb injectors. Pacesetter mids. 1.6RR Tunned by Chuck Summer's. 382/351
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10-11-2015, 01:15 PM #5
OP, as noted in the above post, your long tube headers puts your CAT to far back to light off and burn as it should so your HC's are high. Even if you have lose emission testing in terms of visual (here in Calif you would fail on that alone even if pure oxygen came out the exhaust)
a tune may be able to lean it out enough but the CAT will struggle to get hot enough to burn off spent exhaust enough to pass. Really the whole purpose of "shorty" headers...it keeps the CATS close enough to burn off
you could try a new CAT and 02 (AC Delco)...might get lucky96 BBB 383/T56
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10-11-2015, 03:14 PM #6Founding Member
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I'm in delaware and having the same problem now too. Last time I went through with the exact same setup I passed with no problems. Now hearing this I am really thinking they do not have a clue how to do the test right. We need to talk.
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10-12-2015, 06:42 AM #7Lurker
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I was hoping you would see this post man, I read the thread you had your car and the results seem unfortunately similar lol. As for the other questions yes the cat is brand new and tbh the location of the cat was a concern to me simply because there is no close place to put it with the y pipe merging so far back in the exhaust. The 02 sensors are brand new as of the day of the original post, I had done the heated conversion the night before. The reason for replacement of the other items was not out of strictly to get it to pass but because they were all well pass there life span and I simply like to keep stuff in proper working order. The last thing I want to do is throw parts at it, that's why after much consideration I did take it to a good friend of mine who has 40+ years of automotive experience in emissions testing. I went by his shop on Friday after work and looked the car over again and is starting to think there is either a small vacuum leak or possibly a valve that is not adjusted properly. Thanks again for everyones input on this.
93 FORMULA FIREBIRD, black hardtop, auto, long tubes, ory, ls1 lid,
97 CAMARO SS SLP, black hardtop 6 speed, shorty headers
84 MONTE CARLO SS, 305HO, th400, 3.42's
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10-12-2015, 04:24 PM #8Founding Member
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I adjusted the valves and checked for vacuum leaks and still failed. The 3rd time thru at DE City the dude admitted he didn't know how to do the test. I still failed. Pm me here and we can catch up. I'm in the Odessa area. I'm currently looking for someone with fresh eyes to look over my crap. I am planning on waiting till 2016 to tag it. Get 2 years and then go for antique.
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10-13-2015, 02:54 PM #91997 Pontiac Trans Am WS6 clone | Build Thread | - just needs paint!
2001 Chevy Silverado 2500HD (the DD)
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10-13-2015, 03:40 PM #10Lurker
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@Spartan7 in theory one could pass smog in CA with LT's and reg universal cats with a "smog cam" and a really spot on tune?
Sent from my iPhone using TapatalkArctic White 1996 Z28. Stock internal LT1, CAI, LM1, MGW Shifter, 3.73's, some suspension junk, and shiny salad shooters (retired). Forgestar F14's 18x10 on all 4. Fun stuff coming soon. Also, Cali smog regulations suck...period. **Insert witty quote here** LT1FTW that is all. Have a nice day.
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