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04-30-2009, 05:29 AM #1
WONT PASS SMOG!! running too rich!
went to take my biannual smog test to renew the registration today and failed, ran too rich and cant figure out why?
ran it to get more than warm enough before showing up for the test, havnt made any changes to the fuel system. still dont know whats wrong. if anyone has tips or checks id gretaly appreciate it before spending the over priced fee of getting the diagnostic.
the test results:
Hydrocarbons max @ 15 mph is 118 ppm/ MINE was 172 FAIL
Hydrocarbons max @ 25 mph is 98 ppm/ MINE was 156 FAIL
CO max @ 15 mph is 0.68%/ MINE was 1.07% FAIL
CO max @ 25 mph is 0.87% / MINE was 0.56% PASS
thanks!!90' Chevy Silverado 1500
Suspension: Belltech 2" Drop Spindles
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04-30-2009, 09:58 AM #2
My 89 Suburban didn't pass a couple of years ago and it seemed to run fine. We replaced the EGR, no change. Did a full tune-up, no change. Replaced the Cat, passed with flying colors.Gary
99 K 1500 Suburban
78 Silverado Big 10 w/factory 454
00 S-10 Blazer
1976 Trans Am
1980 Honda CB900 Custom
05-04-2009, 06:32 PM #3
yea i was thinking it might be the cat, although i did put the cat thats on it in new about 6 years ago, i wouldnt think it would go bad that fast.
i did recentlly change out my spark plugs before taking the test because it was lagging in take off power and found one of them (or maybe more) had been burnt up and wasnt combusting (dead cylinder).
do you think because of those cylinders not firing over time could have jacked up the cat converter because of all that air and fuel mixture going through unburnt?
i just dont want to waste the money on a diagnost. if i can figure it out myself. lol
05-05-2009, 06:10 AM #4
Use a scanner and check your O2 sensors. If they dont come out of closed loop it can cause the same issue.
05-05-2009, 08:03 AM #5
Your cat is probably shot. Running raw fuel through it will kill it prematurely. A bad O2 sensor will set an O2 code.Jim
2004 SILVERADO 2500HD LS
Pro Comp Leveling Kit
285-75-16 Cooper ST All Terrains
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Linux Bed Liner
1967 Landcruiser <350 Chevy>
1990 Geo Metro Convertible
2007 FJ Cruiser
05-15-2009, 11:53 PM #6
thats what i figured.
takeing it in for diag. scan on mon, let yall know the results.
thanks for the help as always!!
05-16-2009, 10:14 AM #7
Diagnose it properly. Running rich will kill cats, but replacing the cat doesn't fix the running rich problem, which means the new cat will have a short life.
I'm not familiar with diagnostics on the TBI motors. Back when I had an '88, you could pull trouble codes by simply jumpering two terminals on the ALDL -- I fully expect your '90 has the same functionality: http://www.troublecodes.net/GM/ If the SES/CEL has come on, I'd probably start by pulling codes (as easy as it is, I might pull codes even if it hasn't been on). The primary function of the engine management (aka OBD1 system) is to control fuel mixture.
I don't know how to check fuel pressure on the TBI motors, but high fuel pressure can cause a rich condition. Check for leaks into the throttle body/intake (such as a leaky injector) which can cause a rich condition.'98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
'92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
"My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World
05-16-2009, 11:21 PM #8
you ever thought of moving out of cali? no more failed smog testbd1326
2005 Chevy Silverado 6.0 Vortec 4X4
K&N Air Filter: Stock Replacement
E3 Spark Plugs
Magnaflow Single Exit Exhaust
Rough Country Leveling Kit
Much More To Come
"Understeer is hitting the wall with the front of your car. Oversteer is hitting it with the rear."
- NASCAR driver "Fireball" Roberts.
05-19-2009, 07:08 PM #9
i was told before to try this to see what codes come up but i figure i might as well go through with the full diagnostic, luckily a buddy has a shop and is taking care of it for me otherwise id be out about $100 to run it. if it wasnt for that id be doing the paper clip method for sure, lol.
and i wish i could move out of cali for all the troubles here and stupid laws, unfortunately the pleasures outweigh the pains.
06-05-2009, 11:16 AM #10
- Join Date
- May 2008
Denatured alcohol. Look i tup online, if you just wanna squeek by it might help you out.
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