sonomacrew01

My 1993 LT1 failed RI state emissions. The car has the LT4 hotcam kit, headers, Random tech. high flow cats. and a 3" B&B exhaust. New O2 sensors, new A.I.R. system/EGR valve. New plugs, wires, opti, coil. I also had the injectors cleaned.

Obviosuly, I need to have the car retuned and since the retune, I've never touched the engine (over a year and maybe 1200 miles). The car was due for a new inspection sticker and it failed pretty bad.

HC PPM at idle = 623, limit was 220
HC PPM at 2500 = 128, limit was 220
CO % at idle = 2.97%, limit was 1.20%
CO % at 2500 = 2.94%, limit was 1.20%

High HC and CO means a rich fuel mixture...correct? If so, is this a tuning problem? Should I start there? If the guy did a bad job at tuning and I've been running rich for 1500 miles or so, should I start looking to replace O2 sensors, cats???

ebisko

Hi, I just had my 94 Lt1 redone last winter, similar goodies, bigger cam, 383 forged stroker. I also did not pass emmisions testing, similar numbers on the test. I went nuts trying retuning , and rechecking all parts & O2 sensors. After (4) retunes and lots of $$$$ it still did not pass. Here in Ontario, we have a conditional pass that the emmisions testing station preformed. Basically they checked the car out and told me that I would have to change the cam. This cost 1 hour labour and with this report, they issued me a conditional pass. I don't know if you have anything similar but this was my way out. I've resigned (?) myself to having this done at each annual test. Now I just enjoy driving the car as it is, and try to forget that the car WILL NOT PASS EMMISIONS TESTING. Hope you have better luck, I'll be keeping my eye on this post. Earl.

STL94LT1

Sounds like you need a good tune, not just a WOT dyno tune. But, one that is done doing part-throttle street driving.

sonomacrew01

I hope so.. I've been testing injectors, fuel rail and O2 sensors. I want to go to a tuner with an understanding of whats going on.

SunCr

You could spend some time tuning, but I'd be more inclined to look for a header or exhaust leak, particularly since they've been swapped out. A scan will tell you what's going on. I'd guess it's adding fuel it doesn't need - which happens when air gets sucked in from some other source.