1. Sorry for the lengthy post, I know most of these things have been discussed before but alas, here I am.
2.I troubleshoot Avionics system on fighter aircraft for a living and consider myself relatively inclined mechanically so try not to insult my intelligence TOO much
3.I HATE paying a shop to do something that I could do myself.....BUT
this has been an ongoing issue for months and now seems to be coming to a point where I'm at a bit of a loss and looking for some advice before I gut my wallet at a dealership or a shop..
-about 6 months ago had o2 sensor issues, replaced all 4 sensors with bosch units (I know..), no fix. ended up being the aft mini-cat totally gutted. So all new cats now.
-Then had a bank 2 sensor 1 code, put the original stock sensor back in, fixed for a few weeks, then the P0152 came back along with a P0300 (multiple misfire). Took apart the TB and fuel injectors and cleaned everything quite well including all sensors on the TB iteself (IAC/MAP/TPS) A LOT of build up in there so it looked promising. Put back together and then had some low rpm stumbling (wasn't there before). Rechecked the plugs (looked good, they were recently replaced-autolights) and put some good cleaner through the tank. I read the Coil pack and Fuel filter/pump are lifetime items so I'm ruling those out for now..
-Stumbling never went away, but ran GREAT above 1500 rpm.
-Then got P0300, P0303, and P0152. Common denominator seems to be either fuel injectors or the 02 sensor. Have been trying to find schematics to shoot all assoc. sensors but the info out there is lacking.
-Did a compression test and the 3rd cylinder was ~160 compared to ~180 for the rest, then a wet test on all and got about 20 psi increase on all respectively, so now I'm thinking piston rings. So for S&G's I put a can of restore in the oil to see if I could get any improvement.
-Just checked codes again and I'm now getting P0300, P0303, P305, P0627, and P0152... the 627 is pointing to fuel control relay circuit. Not sure how as I haven't messed with the tank or assoc parts, only thing was the actual relay when doing the comp test, but that is seated properly. It's running worse now at all rpm's, actually feels like its missing on a cylinder or two
SO, I'm just trying to figure out if this is just a snowball ****show of issues or if there is possibly one good root cause of all of this. Aside from putting yet another rear upstream o2 sensor or fuel injectors idk.
P.S. I've done about as much homework as one could online and via the haynes manual...I'm just trying to minimize the cost of replacing everything twice, or god forbid a complete engine overhaul. I feel like I already know what I'm going to get for responses but at this point it can't hurt to ask. Thanks in advance