Due to the engine management problems of the last 8 months I decided to replace the AFM and O2 sensor prior to RA this weekend. But the O2 sensor was slow to arrive and didn’t get in until last night. So I pulled out the old O2 sensor, that had been used when I installed it from my parts box at Mid-O last June, but then had a helova struggle threading the new O2 sensor in.
After fighting with the new O2 sensor for quite a while trying to ensure that I was threading it in square, I started looking for things to do differently. I figured that I could put the old O2 sensor in and make precise note of exact location of the O2 sensor’s rear. This, so my theory went, would help me put in the new sensor exactly square.
But the old sensor didn’t want to thread in either. So then I looked at the old O2 sensors thread and they were all torn up. They were so torn up that it was a wonder that the sensor had held in place. That told me that the threads in the exhaust bung were all torn up. Oh great. Shit, couldn’t I have just left this alone?
So I tried a while longer to thread in the new sensor and it was a nogo. I thought “maybe I can fix the exhaust bung threads by threading in an exhaust bung plug. The plug will be a helova lot easier to start square.” So I looked around, found the exhaust bung plug I’d recalled and tried fruitlessly to thread it in.
It was time to start thinking about backup plans. I have a 2nd O2 sensor because I have an F/A meter on the dash. I could splice in some wires to make the OEM O2 sensor reach farther and put it in the alternate location. But if I did that I wouldn’t have the F/A meter which is critical to troubleshooting the engine management problems. I could also try to fix the threads on the exhaust bung.
So I hustled out to Harbor Frieght and bought the largest tap and die set I’ve ever seen. It has taps all the way up to something huge like 30mm or so and comes in a metal box the size of a surfboard.
Back home I decided that I should test the idea on the exhaust bung plug so I used the die to fix the threads on it that were slightly goobered up by me trying to thread it into the exhaust bung. By careful use of the die I was able to improve the slightly damaged threads until they were entirely ruined. With that behind me I was ready for the exhaust.
I spent probably 90min trying to repair the threads in the exhaust bung, with hands wedged up past frame member and sway bar, and it wasn’t going well at all. The tap was constantly shifting on me, the force of turning it made it shift. Sometimes it was loose and other times it was practically unturnable. I was using a 10mm wrench to turn it and at one point applied so much force that the wrench snapped. It was really going well, I thought. The idea of saying “screw it”, calling the race weekend a casualty, getting some dinner and several beers was really starting to sound appealing. Who knows, maybe after a couple beers my morale would improve enough that I could take the car to midas and give it to them for the day. Getting the exhaust system off so the bung could be repaired was going to be no picnic.
Getting a bigger wrench I kept at it. At some point I decided that although the threads in the exhaust bung were clearly buggered up, maybe I’d changed things enough that a sensor would “start” threading in. Then we’d see what happened. So I grabbed the new O2 sensor and after some fiddling, it threaded in. This was quite unexpected. So I gently tightened it down, sure with each movement of the wrench that the threads were going to give way in the next instant. And they didn’t. The darn O2 sensor threaded in ok. It might not be threaded in quite tight enough, but it’s pretty darn close. A miracle had occured.
So I loaded the damned car up in the middle of the night, went and got some chow and had a couple beers. Dang that was a pita.