mikem01 Posted January 23, 2019 Share Posted January 23, 2019 05 lgt(stock) has thrown a pending po420 code twice in 2 weeks. Tracking it from a bluedriver and when I turn off the car and go to restart it the code is gone...no idea why. So far I have replaced both o2 sensors (denso), plugs (ngk), one coil pack, replaced the MAP to manifold hose and zip tied all hoses, Cleaned throttle body and replaced the clamps.My fuel ltft stays at about 11-14.8 at idle but drops to the 2-3 range while driving. I'm assuming there is a vacuum leak somewhere but I can't seem to find it. I know it's coming so yes I have checked the "t connector" under the intercooler. I have also looked for rusty spots or holes all through the exhaust. Plan on doing a smoke test tomorrow but curious if anyone has any suggestions or know something I might have missed. Sent from my XT1585 using Tapatalk Link to comment Share on other sites More sharing options...
relative4 Posted January 23, 2019 Share Posted January 23, 2019 Re the fuel trims, you're on the right track with the smoke test. Re the P0420, an infrared thermometer may help you verify if the cat is underperforming. Link to comment Share on other sites More sharing options...
Notorious Posted January 23, 2019 Share Posted January 23, 2019 How many miles on the car? (Assuming the catalytic converter has never been replaced). If you are using the OEM TMIC, it could be leaking from the end caps or from the O-ring gasket on the hot side. If the smoke test is inconclusive I would also check the catalytic converters with an infrared thermometer like relative4 mentioned. Temperature should increase after the cat compared to before by at least 50 degrees. You can find a cheap thermometer at Home Depot for like $20 or sometimes Autozone may have one in stock. Link to comment Share on other sites More sharing options...
mikem01 Posted January 23, 2019 Author Share Posted January 23, 2019 Thanks for the input guys. The car has 160k and as far as I know the cats and the tmic are both original. Sent from my XT1585 using Tapatalk Link to comment Share on other sites More sharing options...
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