P0420-After Complete Exhaust Replacement
A few months ago, my car threw the TC P0420. I didn't have the money to deal with it then, but over the last 6 weeks, I've been trying everything I can to no avail.
First, I took it to the shop. They charged me 400 for an upstream sensor. CEL came back on. Then, they said I had to replace the cat. So I buy one off Ebay (premium based on manufacturers specs) and that didn't work. Code came back. So finally, I figure there is only one possible problem left. The downstream O2 sensor. So I buy one and replace. CEL came back! At this point, I'm confounded so I research some more, and try the spark plug savor MOD. Essentially, it pulls the sensor out of the stream. Runs rough until computer calibrates, then it starts running REAL bad. Not shifting correctly, at the right RPM's, and trans makes dropping noise when I shift to D or R. So I climb back under there and pull the MOD off. I had unplugged the battery while removing that MOD, but not 10 minutes into test drive, the CEL came back on. I figure the computer needs to relearn the operation protocols.
The engine runs a little better after removing MOD, but trans is still kinda slamming into 2nd, and a tiny bit in 3rd and 4th. I plugged the monitor in this morning and it gave me 10 different, exhaust/vacuum related codes. I figured it is still figuring stuff out so I reset it, and test drove it again. 15 minute test drive and no problems except for the slight gear slippage into 2nd. I turned the car off and when I turned it back on, CEL reposted. Typically, it takes a week for the CEL to throw the P0420, but now, my CEL hit fast.
What am I gonna do about this thing? I bought the parts, and did all the work myself cause I'm broke. When I do take it to the garage, They are gonna create a huge list of vacuum leaks, and god knows whats else to try to charge me for. Any insite, or reassurances would be totally appreciated.