Hey guys I have a mp112 on my 5.3, If i'm under part throttle accelerating or while Towing I could be at 3-5psi part throttle and showing 11.5 on my a/f and it will suddenly kick out 4-5 seconds into it and go back to 14.5 or so. This does not happen at WOT. My tuner is going to hook up his lab top and see if the computer is still commanding 11.5 when it kicks out and see if its a fuel issue. i'm only running 3.3 pulley on a 5.3 with ls1 cam and catback. I have 42lb 8.1 injectors. I should not be running out of fuel during partial throttle. I'm going to change fuel filter tonight.

Any change its a returnless fuel system issue? Any tuners run into this ? My truck is a 05 5.3 non flex.

 

Could be the rpm and map value conflicts in the pcm. What does your a/f look like under full boost and throttle? That will tell you if its a fuel system issue

 

If I'm WOT I can old it there all day. a/f shows between 11.3-11.5 Never have had an issue WOT. Just partial throttle it goes crazy after a few seconds and kicks out of p.e. mode

I get a system to rich code bank 1 and 2 p0172 and p0175 occasionaly as well

 

Let us know what the tuner find out. There are a few tables that control PE and when it comes in. If you can post the log from your tuner if he is willing to send you the file.

Is he using HPT or EFI Live?

 

Are you on a factory OS or a custom OS for FI?

 

I am betting your falling below the TPS % required to enable PE even thou your MAP range is above 1-2psi.

If your on a factory OS have him set your commanded AFR for MAP ranges above 90kpa to 11.5ish.

 

ok, I will ask him what he is doing with it. I'm pretty sure he would have adjusted all of that, He uses efi live and has a turbo on his own vehicle that he tunes and does not encounter this issue.

 

When it kicks out if you give it 10-20% more throttle but not go WOT will it enable PE again? I think Corey is on the right track.

Be careful about it not staying in PE when in boost though. It can cause a bad day pretty quick...

 

I have not tried to give it more throttle once it kicks out of pe, Everytime it kicks out I just let off the gas immedietely, I dont want to force it to boost when its lean. I can try and blip the throttle next time and see if it drops down again. My buddy is going to hook up efi too it again tomorrow and see if we can figure some things out.

 

WEll I swapped my maf to see if anything changed, and nothing. If i'm going part throttle at say 40mph in second or 3rd and showing 3-5psi it will show 11.5 then pop out to say 14.5 if i slightly let off it will go back in to p.e. mode, i can then give it a little more throttle and it goes right back to 14.5+ so basically if i let off it pops back in and if i hit it again it goes back out of p.e. I've already done a wot pull from 0-90 with no issues. stayed around 11.5 entire time. Only thing I can think of is possibly fuel pressure regulator is loosing pressure in the system under medium load and cannot regain. where as if i hit it from a dig it holds pressure. does not make sense what so ever. I'll tell ya one thing, its really hard to pull a trailer that has any weight!!