Hello folks.
Car is 1997 GTP with 90k miles. Strong runner and well kept. Mods include 3.25" pulley with supporting mods and meth injection.
I had meth injection installed yesterday, 50/50 mix, comes on at 6psi , with my max boost being near 13psi. First question : I had 5 degrees of knock at WOT before installing the meth kit. After installing the kit I was able to test it only briefly before going to bed, and the 5 degrees WOT knock was still there. Today however, I am not seeing more than .5 degrees knock after extensive testing, and it is the same weather conditions. Why might this be? It seems as though the meth kit is now doing its job perfectly. *note* The knock most commonly occurred with a hard downshift during WOT. If I eased into WOT I had virtually no knock at all.
Second question: For a month or so now I had a p0420 code appearing (Catalyst System Efficiency Below Threshold (Bank 1) but I assumed it was just my high flow cat triggering the code (as per research online). Today however (approx 2 days after installing my meth kit), I went to start my car and it just sputtered and quit. In order to get her going I had to give it a little gas while starting the car. Also, there is now a mild hesitation/sputter occasionally when accelerating from a dig. Performance after initial acceleration is fine though, which makes me think it is not the cat. Is it merely a coincidence that this happened shortly after installing my meth kit, or is related to the p0420 code which has been lingering for a month, meaning a bad cat or O2 sensor?
Thank you in advance,
J
Originally Posted by The Sunfire Guy
