Hello! I made a post awhile back about this same issue, I received a lot of really good help, but that was over a month ago and I'm still stumped so I figured I should reach out again. I've got a 1976 K10 with a 350 TPI, replaced the motor because cylinder 6 piston blew up. The motor is re-manufactured. While I was in there I replaced all ignition components, fuel injectors (22lb/hr from napa, I regret not doing more research before hand on injectors), cts, map, iac, and some other stuff. I've got timing at 6 degrees before top dead, and my wires are all where they need to be. I probably only have about an hour of run time on the new motor and the plugs are already black as night. I've got good fuel pressure, and it holds after the vehicle is off. Just for kicks I turned the key on, let the fuel pump prime and pinched off the return line to verify that my new injectors weren't leaking. I've checked and rechecked distributor orientation about a dozen times. Smoke tested for vacuum leaks through the booster hose with the throttle body plugged up, found two little vacuum leaks and took care of them. Noticed that bank 2 header were heating up a lot faster than bank 1. Typically the bank 2 header gets about 100 degrees hotter than the bank 1 header. Cylinders 4 & 6 are usually about 50 degrees hotter than 2 & 8. I removed the cat for bank 2 and found that to be pretty plugged up with pieces of piston that blew up in the old 350 (still kicking myself for not doing that sooner), so I just ditched the cat. After correcting exhaust restriction I started it up and it was still idling rough and hunting. I held the motor at about 1,100 rpm for a minute or two and it ran much smoother at that rpm. Immediately after that I checked the exhaust temps with an infrared thermometer and bank 2 was at around 450 degrees while bank 1 was significantly cooler. Pulled the header off bank 2 because I thought that maybe that got plugged up, but everything seems to be okay. The previous owner of the truck wired up a heated o2 using the o2 out of a ford bronco, pulled power from the fuse block, and grounded it to the frame. I'm going to give the stock o2 a shot and see if that helps at all, but I'm sure that an o2 can't be the cause of all of this. I'm thinking that I've still got vacuum leaking from somewhere because of the hunting idle. I noticed that I've got some oil leaking from the back of the engine, I believe that the leak is where the intake meets the block. Is a vacuum leak from here possible? I also never checked to see if the vacuum canister is leaking, so I'll need to check there.

Could something ECM related be the cause of these issues? I'm pretty unfamiliar with these OBD1 computers, so I don't even really know what I'd do to verify that everything is operating as designed. I know that you can sometimes diagnose a bad ECM by hitting it with the engine running, but other than that I'm clueless. The fact that I've got injector pulse and it'll give me codes makes me think that the ECM is okay, but I'm unsure if the previous owner maybe put an aftermarket prom or something in there that is causing issues. If this is a possibility, how might I check for this?

Any suggestions/ideas of something I should check that I might have missed, points in the right direction, or help of any kind is much appreciated! Sorry for the wall of text, and thank you for reading!

 

You have too much fuel on all the cyls of bank 2.

Most likely, this is because the O2 sensor is in bank 1, but bank 1 injectors aren't working; and the ECM is fueling the thing like crazy to get the O2 indication up to snuff. Which is hard for it to do because any fuel that gets to bank 1 has to come over sort of accidental-like from bank 2. Which thus ends up DROWNING bank 2.

We call this process "feedback". It is independent of OBD1 vs OBD2 etc.

I'd start by checking the 2 INJ fuses. Then I'd check for the presence of injector pulses on all 8 injector connectors.

Doesn't matter that the O2 is "out of a frod bronco". O2 sensors are a simple chemical thing, all the same. (apart from wideband UEGO types, which are a whole other unrelated matter) Only thing that makes one different from another is the connector style and the presence / absence of a heater. They're even all (or at least the VAST majority) the same thread. Bosch holds the patent and licenses it to EVERYBODY ELSE.