Running Lean at Idle and Throttle Sputter
I have installed the Fitech on a SBC in a 71' C10. I had everything working great with no throttle lag or lean AFR. I was driving the other day and suddenly the AFR jumped up to around 17 and when I hit the throttle it went supper rich and sputtered. Idle was running an AFR of about 18 and no matter what I adjusted I could not get it to come down. I called Fitech, and they said it sounds like an exhaust leak pulling air in and making the O2 sensor report incorrectly. I had the clamp on the O2 bung so I welded that, verified all other gaskets were good and bolts were tight on the exhaust. This improved the AFR, but it is still hovering around 16 to 17 at idle and when I hit the throttle it jumps to 20 then back down to 12 to compensate. I have adjusted the accel pump and normal acceleration is good. When I hit the throttle harder the AFR jumps to 20 then back to 12 with a lot of backfiring. I adjusted the fast accel in increments of 10 both ways to the max, and have gotten no improvement.
To recap my main issues are high AFR at idle and super high AFR/backfiring on fast accel. Any help would be greatly appreciated.
Sorry forgot. I have the IAC hovering between 8 and 10.
Have you tried unplugging the O2 sensor and letting run open loop? See if the performance issues still exist.
Ok so I disconnected the wiring harness on the O2 sensor. The truck would run, but it would idle up then almost die, and repeat. The IAC steps would not go down from 225 and the AFR just read 14.7. The acceleration seemed to be better. I plugged the sensor back in and the truck would not idle below 1300 RPM, and the acceleration was still an issue. I decided to load a good backup and now the truck will start for about 5 seconds then die. I can keep it running if I give it gas and once the IAC steps come down it idles fine. The acceleration issues are back though.
Do you think I have a bad O2 sensor? I will replace tonight and see if that helps. I don't understand how it could go out so fast. I have only put maybe 50 miles on the truck since I put the Fitech on.
I tried to make a datalog, but when I plug the handheld into my PC there is no log_file folder. Is there a certain amount of time I need to log for?
Thank you again for your help.
If the issue was your O2 sensor then your engine would have ran better with it unplugged. You have another issue. Vacuum leak, exhaust leak, not enough exhaust length past sensor, etc.
When you log, you must let the ecu power down before you unplug the handheld.
Aside from the idle moving up and down it did run better. Acceleration was better.