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suggestion/help for failed CA smog Posted by ryan [Email] ![]() ![]() |
Wanted to see if we could get any suggestions on a failed CA smog issue. This is for an '88 900 Turbo, only modifications are a SAAB redbox APC and a SPG9/Group9 3" stainless-steel turbo-back exhaust. With this setup, the car had passed smog for half a decade, no problem. 15mph HC and NOx were always a bit high, but from looking at other's tests, it seemed typical for a 900 Turbo. Two years ago it started having problems passing smog, the assumption was that the catalytic converter on the SPG9 system was finally wearing out.
So, this year the car failed, failing in everything (HC, CO, and NOx) in the 15mph test, and getting pretty close on the 25mph test in HC and NOx (but passing). For 15mph, HC was 129 (max 116), CO was 0.60 (max is 0.52) and NOx was 1667 (max is 791). For example, in 2008 these numbers were 105, 0.19, and 782. In 2006, they were 82, 0.19, and 778.
Put on a new 3-way Magnaflow California catalytic converter (33009) on the car, expecting this would set everything straight. Now the car passes HC and CO across the board, but fails NOx in both 15mph AND 25mph. The 15mph numbers came down from before (maybe 300 points), but the 15mph numbers went up past the max allowable of 730. Figured that the new low HC/CO numbers and high NOx meant high-combustion temperatures and therefore a lean fuel mixture. The fuel mixture was made more rich and the car was driven 50 miles or so to 'break-in' the catalytic converter. Tested again and the NOx numbers actually went even higher.
So, we are a bit of a loss at the moment. The car has a relatively new O2 sensor, the AMM was replaced a few years ago. The car only gets 91 octane and every six months gets Redline fuel injector system cleaner. The engine runs very strong with 216,000 miles, only issue is it consumes maybe a quart of Mobil 1 0W-40 after 5,000 miles.
posted by 108.88.224...
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