AFR climbing without changes to truck
 

Hey guys,

I posted a question in the forced induction section (https://www.performancetrucks.net/fo...-truck-549631/) but wanted to post up a couple data logs I took tonight in this section to hopefully get some help.

Long story short, I haven't made any changes to my truck but the AFRs have recently been climbing into the high 12s and even a 13 at WOT. I've been told to check my fuel pressure but I can't see it in my log file. I've attached a couple logs I took tonight. Maybe one of you guys can help me.

Right click on the PID you want to change and select the new PID for that row from the list.

Your FP drops to 50 PSI in boost. But AFR looks a little rich, not lean.

Still a 1 bar MAP sensor?

Thanks for the reply DrX. I did figure out how to see fuel pressure late last night. I pulled an old log file from before I had the issue with the AFRs and the rail pressure was dropping about the same amount it is now. I'm still on the stock MAP sensor. I'm ok with it running a little rich because it's my daily and I'm not looking to blow the thing up!

I'm beginning to think the small exhaust leak I can hear in the morning might have something to do with this...

If the truck really was leaning out wouldn't it affect the LT fuel trims? I'm seeing negative numbers there which I thought meant the truck was pulling back fuel because of a rich condition...I'm not too familiar with tuning though so I could be off-base with that assumption.

LT fuel trims will not learn at WOT with narrowband O2 sensors. A lot more information is necessary: calibration strategy, ie SD, MAF, hybrid, etc; wideband sensor placement; air intake routing; IAT sensor placement, and a number of other things.

Thanks for the lesson, smoke. I don't know if you can take a look at those log files but if you can do you see anything I should be worried about?

I'm pretty sure I have read somewhere that ltfts can eventually cause your wot fueling to change.

https://www.hptuners.com/forum/showthread.php?54025-LTFT-changing-WOT-tune-over-time

If someone wants to maintain LTFT functionality but does not want potentially poor calibration of airflow estimation corrupting the LTFT values applied at WOT, I recommend setting the highest fuel trim cell MAP enable thresholds to a high value. This will prevent learning in those cells due to the truck entering power enrichment prior to entering those fuel trim cells. For example if your high MAP cell boundary is set to 75kpa, move it up just a few kpa shy of a realistic barometric pressure. For a boosted application, you can set the value in the boosted range if the software allows. However I'd suggest something like 90-95kpa to start. This applies to port injection controllers...not sure how GM is handling direct injected fuel trim cell boundaries. Probably a little more complicated now :)

It just got REAL complicated, smoke. Thanks for that! haha. I'm trying not to make it so complicated. I haven't made any changes to the truck so theoretically it should be something simple, right? I'm going to clean the MAF sensor and collect another log file. What are the symptoms of a wideband O2 sensor going bad? I bought the wideband used about a year ago...

I'm really hoping that the truck isn't running as lean as the wideband is telling me. I pulled an old log file from a few months ago and everything seems to be the same. FRP is similar, fuel trims are similar. I'm not a tuner so I don't really know what to look for.

Thanks for the help so far, everybody! Keep the ideas coming! If you need any more information just let me know.

Alright boys and girls, I've got the truck running back like it did before I started having issues! I feel a little foolish but it was an easy fix. I cleaned the MAF, tightened up some clamps on the intercooler piping and a v-band on the crossover, and cleaned the wideband O2 sensor. Now I'm seeing mid 11s on the wideband at WOT, which I'm much more comfortable with.

Just thought I post up my resolution so that if anybody else is having an issue they can reference this thread.