Obtained a timing light. Discovered that my base timing was WAY off (yes I disconnected the SPOUT plug)… fixed that, but no change to symptoms. The symptoms have evolved to a mostly consistent low, rough, and unstable idle which often stalls out when in gear (and sometimes when not, even with the A/C off). Bad enough for me to park it and drive my other truck instead 🙁
I then ran a fresh KOER test. I received codes 12 (idle too low), 13 (idle too high), 23 (TPS out of range, may have been my fault for not mashing the gas at the right time), 41 (O2 sensor reports lean), and 73 (another TPS code, likely due to my goof on the throttle hit).
From this, I’m suspecting either:
- I still have a bad vacuum leak
- The carb’s idle circuit has an issue, despite being rebuilt
- There is a partial misfire that is not burning all the fuel (shows as lean due to unused O2)
- The O2 Sensor is faulty and actually making it run way too rich
My fuel economy is garbage too… if that makes any of these more likely.
Also odd is that the RPM range was faulted as both too high and too low. If this wasn’t an idle-only issue, I’d suspect a distributor pickup/wiring problem. However, I seem to be getting consistent spark, so I doubt that’s it.
I took a video of it idling… but the video doesn’t seem to show the “roughness” well. Also, something in body is knocking from the rough idle… which made it sound like I’m about the throw a rod (not the case!). If this helps, I can upload it to youtube anyway.