AFR zooms to 20.6!
I have a 30002 600 throttle body. I've run this unit last year with much success with my 350 sbc. This winter I rebuilt and stroked it to 383 and put it back together with basically the same pieces, i.e. heads, headers, intake and so on. Bottom end is fresh.
Now the car runs fine at first and then Afr rapidly climbs to 20.6 and the car stumbles dies etc. Plugs are seriously fouled and the 02 is likewise fouled. I've tightened all possible exhaust connections till my knuckles hurt and checked for vacuum leaks. Everything appears fine. I called Fitech and they suggested I reload/flash the ECU so I did that as well. Actually that seemed to work for awhile. I took it for a spin and it never ran so well. Snappy, good idle and no hesitation when you get in on it. Good times! Until the next time I took it out. It behaved at first and then went back to 20.6 afr. I decided to drive it to town, 1/2 hr trip, but it remained at 20.6 and once or twice blipped back down to 13-14 where it should be, but only momentarily. Each time it did that the car performed as it should. The idle was OK but big hesitation when I throttled it a bit.
When I was ready to return home, it ran so bad that it sounded like it was running on 7 or even 6 cylinders. I was barely able to make it home. I checked this am. and the plugs are bad, however the oil doesn't appear to smell of gas. I'm going to order a new 02 sensor, but other than that, I'm not sure what else to do other than reload the software again. Could it be a stuck injector? How does one remove or replace an injector in these units? I'm going to remove and check all the plugs tomorrow. Perhaps that might tell me something I don't already know.
Any suggestions would be helpful
Thanks , Richard
I know you have checked for exhaust leaks but this sure sounds like a leak. I've got exhaust cutouts - when I open them at idle my AFR raises to 20+. Had to extend the cutout pipes. I think something is opening up and causing a leak at temperature. Can you move the O2 sensor to the other side of the exhaust?
Quote from 69_R-Code on July 8, 2021, 7:56 amI know you have checked for exhaust leaks but this sure sounds like a leak. I've got exhaust cutouts - when I open them at idle my AFR raises to 20+. Had to extend the cutout pipes. I think something is opening up and causing a leak at temperature. Can you move the O2 sensor to the other side of the exhaust?
I know it does. That and vacuum leak are the prime suspects. I'm going to disconnect header and examine gasket and both flanges for possible leaks. I know on that bank, the header and pipe needed persuasion to join. Perhaps there is a leak right there. I'm also going to do a smoke test for vacuum leaks. I'm ordering an 02 as mine is pretty shot. Also going to check the weld on the 02 bung to make sure it's not leaking there.
As an update, I think I may have discovered the root of the problem. For those who are interested, I believe the pressure regulator is to blame. After watching this video
I decided to check for fuel in the vacuum line of the regulator. It poured out some fuel. I've just changed my 02 sensor and checked all gaskets for a good seal, which they were, so I've ordered a new regulator and will let you guys know if this was the issue all along. Makes sense to me. Ruptured membrane would cause fuel pressure drop signaling a lean condition. I'm going to install a remote pressure gauge inside the cab to monitor pressure going forward.
if the a/f ratio went up to 20.6 it definately be 02 sensor fault.
had a issue where it did that, at the time i could only get a lsu 4.9 sensor which fitech said will definately work.
it did not.
managed to get the lsu 4.2 sensor with differant connector cut the differant end of and soldered on the orig fitech connector. worked perfect.