92 Z28 emission issues
Thread Starter
Junior Member
Joined: Dec 2010
Posts: 20
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From: Texas
Car: 92 Camaro Z28
Engine: 355 HSR ProComp heads
Transmission: 97 Fbody T56 6spd
Axle/Gears: Stock 3.23 10 bolt posi
92 Z28 emission issues
K so I've been on here awhile picking up lots of useful info but never posted, and I'll try to be as brief as possible.
I have a 92 Z28 with an L98 TPI 350 and 700R4. It's all stock except a flowmaster muffler and has supposedly 103,000 miles or so on it if I'm to. Believe the odometer.
It won't pass Texas ASM emission test.
This was the first test
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 113 pass 117 / 111 pass
CO .63 / .92 fail .65 / .99 fail
NOx 796 / 830 fail. 879 / 931 fail
Second time after RXP treatment and 3/4 tank of gas run thru it....it was down to........
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 100pass 117 / 99 pass
CO .63 / .80 fail .65 / .82 fail
NOx 796 / 552 pass 879 / 620 pass
So that was passing fairly well except the CO still off a good .17ppm, so I then checked the timing and it was so retarded that it wouldn't even read on the pointer! I thought to myself - great, put back to 6* stock and all should be good to get it to pass now!
WRONG!!
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 295 fail 117 / 350 fail
CO .63 / .60 pass .65 / .62 pass
NOx 796 / 1800 fail 879 / 1999 fail
I'm not sure what's up now cuz prior to taking it for the first test we did a major tune up on it....
E3 plugs
Oil and filter change and flush
Air filters
O2 sensor
New thermostat and flush
Scanned with a snap-on scanner....everything normal, no codes
Compression checked at 150psi in each hole warmed up.
Any ideas guys?
I have a nasty feeling it's the cats, but I'm hoping you guys have some better ideas!!
Thanks guys
Darren
I have a 92 Z28 with an L98 TPI 350 and 700R4. It's all stock except a flowmaster muffler and has supposedly 103,000 miles or so on it if I'm to. Believe the odometer.
It won't pass Texas ASM emission test.
This was the first test
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 113 pass 117 / 111 pass
CO .63 / .92 fail .65 / .99 fail
NOx 796 / 830 fail. 879 / 931 fail
Second time after RXP treatment and 3/4 tank of gas run thru it....it was down to........
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 100pass 117 / 99 pass
CO .63 / .80 fail .65 / .82 fail
NOx 796 / 552 pass 879 / 620 pass
So that was passing fairly well except the CO still off a good .17ppm, so I then checked the timing and it was so retarded that it wouldn't even read on the pointer! I thought to myself - great, put back to 6* stock and all should be good to get it to pass now!
WRONG!!
25mph(standard/actual) 15mph(standard/actual)
HC 114 / 295 fail 117 / 350 fail
CO .63 / .60 pass .65 / .62 pass
NOx 796 / 1800 fail 879 / 1999 fail
I'm not sure what's up now cuz prior to taking it for the first test we did a major tune up on it....
E3 plugs
Oil and filter change and flush
Air filters
O2 sensor
New thermostat and flush
Scanned with a snap-on scanner....everything normal, no codes
Compression checked at 150psi in each hole warmed up.
Any ideas guys?
I have a nasty feeling it's the cats, but I'm hoping you guys have some better ideas!!
Thanks guys
Darren
Joined: Oct 2001
Posts: 12,230
Likes: 1,157
From: Il
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: 92 Z28 emission issues
Ditch those plugs and put AC delco plugs in it. No platinum or new plug of the week just a good standard plug works the best..
Not saying it will fix your problem but I havent heard many good things bout those plugs.
Not saying it will fix your problem but I havent heard many good things bout those plugs.
Thread Starter
Junior Member
Joined: Dec 2010
Posts: 20
Likes: 0
From: Texas
Car: 92 Camaro Z28
Engine: 355 HSR ProComp heads
Transmission: 97 Fbody T56 6spd
Axle/Gears: Stock 3.23 10 bolt posi
Re: 92 Z28 emission issues
Wow, no suggestions other than swap brand new plugs for cheaper new plugs?
I was hoping to get it to pass stock just as it sits but if I can't find a better solution I'll have to go ahead and throw my EBL P4 Flash ECM and WBO2 on and manually create a passing program while on the rollers.
Maybe someone else will chime in with some better ideas
Thx guys
I was hoping to get it to pass stock just as it sits but if I can't find a better solution I'll have to go ahead and throw my EBL P4 Flash ECM and WBO2 on and manually create a passing program while on the rollers.
Maybe someone else will chime in with some better ideas
Thx guys
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