Failed IL IM240 test for the second time in my TTA, and am looking for advice [note that all values below are GPM.] The car is in great shape and runs well w/22k mi and ran a 13.4@103 last summer at Route66 w/a crappy 2.2 60' in 90+ deg heat and very high humidity (pump gas and street tires.) Only mods to the car at this point are K+N, jacob plug wires, adj fp reg, adj wg, valvecover breather (replaced with stock cap before tests), 3" cat, 3" edelbrock cat back, and thrasher 93 chip (replaced w/stock chip before tests.) FP was left at 45 (line off.)
Here's the lowdown. I took it for the first test w/o realizing that the stock cat had been previously gutted (doh!) It also had a bit rough of an idle. It failed w/an HC of 3.6 (limit .80) and barely passed CO w/14.2 (limit 15.0.)
This is when I checked the cat and found it gutted, so I replaced it w/a 3" high flow unit. I also replaced the (lazy) Bosch O2 sensor w/an AC Delco and replaced the spark plugs (AC R42LTS's, gapped at 0.35".)
The idle improved quite a bit, and the idle vacuum reading on the autometer boost gauge went from 12-13 to 15-16.
Took it back for the second test, only to fail again! This time, it read HC 1.88, CO 8.7, and CO2 347. (NOx is not read on their tests.)
I know that the high HC indicates unburned fuel, but I'm not sure why this would be. I'm hoping to get some TL readings to help sort it out, but I have very little time left to get it to pass. I've thought about lowing fp, but I don't understand how this would help on a closed loop system (unless BLM's are off the chart) and would think this might even hurt results by worsening the injector spray pattern? Any help appreciated.
Here's the lowdown. I took it for the first test w/o realizing that the stock cat had been previously gutted (doh!) It also had a bit rough of an idle. It failed w/an HC of 3.6 (limit .80) and barely passed CO w/14.2 (limit 15.0.)
This is when I checked the cat and found it gutted, so I replaced it w/a 3" high flow unit. I also replaced the (lazy) Bosch O2 sensor w/an AC Delco and replaced the spark plugs (AC R42LTS's, gapped at 0.35".)
The idle improved quite a bit, and the idle vacuum reading on the autometer boost gauge went from 12-13 to 15-16.
Took it back for the second test, only to fail again! This time, it read HC 1.88, CO 8.7, and CO2 347. (NOx is not read on their tests.)
I know that the high HC indicates unburned fuel, but I'm not sure why this would be. I'm hoping to get some TL readings to help sort it out, but I have very little time left to get it to pass. I've thought about lowing fp, but I don't understand how this would help on a closed loop system (unless BLM's are off the chart) and would think this might even hurt results by worsening the injector spray pattern? Any help appreciated.