Commanded AFR Changes While Driving

[Earwax]

Hi, I`m new to using HP Tuners. I have a 2005 Silverado 5.3 that I swapped a mild 6.0 into.I had a mail order tune that was rich, I posted the issues and got great help from this forum.I`ve been reading and experimenting with various settings on my tune. I was able to gain over 3mpgs from these changes. the truck runs fine. I have noticed a problem while at part throttle that it goes rich by about a point of AFR.From 14.6 down to 13.6.The O2 sensors confirm that it is rich. It appears to be stuck in this rich mode for a short time and then it commands 14.6 and straightens out? I looked over the log and I can`t find a reason for it to command the AFR change.I would appreciate it if someone with greater experience than I currently have would help point me in the direction of what may be causing this.I don`t think this occurs when the laptop is plugged in? Thanks for the help,I really appreciate it. Thanks,Bill

[5FDP]

Do you have the cat converters still and are the rear o2 gone??

If the rear o2 sensors are not plugged in, the vehicle will run a cat test that you cannot turn off. Just having them plugged in and zip tied to the frame will stop said tests.

[Mep_q8]

any misfire codes? when you get a logged misfire, your fuel enrichens. Max out the misfire tables if you have a cam installed. Message me if you need any help.

[Earwax]

5FDP,Trailblazin: thanks for the response. Sorry I left the Cat info out. Yes it has cats and rear O2 sensors.The only emission item that was changed in the tune is the Miss fire codes were disabled by setting the ETC to 284*for both enable and disable.It would set a P0300 if it idled for 10 minutes.I also have LT headers and a 3" y pipe with cats and 4" exhaust.I drove it today with out logging it and it did the same thing on the wideband. It occurred right after I was in DFCO and reapplied light throttle. It had about 12" of vacuum when it occurred. When it was in this rich mode, I could change the AFR with the throttle.I could lower the AFR into the 10-11 AFR with low vac(8" or so).Almost like it was in PE,except the rpm was too low as was the TPS.The MAP was probably close to its 87 kpa? I am thinking that the MAP may be intermittent or it has to do with DFCO? I`m going to try changing the DFCO settings and then check the MAP and wiring. Here is a list of what was done to the motor: It was an L33, I built a LY6 for it. I kept the crate engine(heads,injectors,intake) except for a 160*thermostat,Comp cam (212/[email protected],.558/.563-114 LSA),Long tube headers with cats,CAI,4 " exhaust.I changed the Crank Reluctor to 24 teeth and the cam sprocket to 1 tooth.
link to earlier post:http://www.hptuners.com/forum/showth...ail-order-tune
Thanks again for the help.I appreciate it. This HP tuner is a great learning experience for me.
I`ll post my findings. it may help someone else.

[Earwax]

I finally had time to check this issue further. The MAP sensor and wiring were ok. I found that I had the DFCO entry RPM set too low.This was in 3rd gear.Apparently,it was too close to the RPM that 3rd produced at part throttle? I raised the entry RPM to stock L33 specs in 3rd (1600) and the problem was gone.I think that being the trans is 1.00 to 1 in 3rd.It is very slow to rev,that and the low DFCO RPM entry speed caused it to stay rich until the RPM was higher than the entry RPM? I`m probably wrong about this theory,but I`m learning.