I just tested my car at work on our machine. Thinking it would pass. 91 TPI (swapped from a TBI). Runs great just some detination on hard acceleration. bumped the timing up from 0-6 deg.(run 89-91 oct. )all the time, anyways my HC at Idle was all over the place 270-500 Co was about .60-1.12 off Idle HC was between 60-230 Co up to 2.00 car runs fine . used the scan tool. Block learn was 150+ inter. was 130 so there is my pinging problem. but why is the exaust so rich. only thing Not conneted is the egr silinoid. and that would make it run even more lean . injectors were bought off ebay I think they are 21 lb not to big (5.0l) injector pulse is 1.6 ms
another thing I noticed was the o2 would go to open loop at idle I thought that was a problem but the scan tool said that some o2's due that on some cars. It would go back to closed if I hit the gas though sometimes it would take about 10seconds. The o2 has about 50,000 miles on it maybe 3 years old. the cat is stock as far as I know (car had 80,000 when I bought it ) No major mods the motor( muffler,gear change, stock chip, afpr , ) I think either O2 is lazy, Injectors too small, cat not working or all of the above. any ideas?

 

If your car has the air pump still on, slip the belt off and see if there is any difference. Could be a faulty diverter valve. Pumps too much air at idle, tells the car it is lean and then it goes to open loop. Mine would even go to open loop on a long down hill at lower speeds.