My truck started running lean at WOT all of the sudden (like 15.1)!

I got my tune from PSP everything worked fine for a couple of months. I have the Excalibrator II, so I was able to set the air/fuel up to 14% richer at WOT in the tune.

This did nothing!

I think the tune is fine, but my truck no longer knows when it's at WOT. I checked the TPS and it's at .992v closed and 4.3v wide open (using a Billet-Flow throttle body).

It is much cooler outside, and I have upgraded to a LFP heat exchanger and a JLP intercooler tank. My IAT temps are super low. Would the cooler, denser air cause this?

Help!

 

Definitely sounds like something mechanical has changed. I'd start with a fuel pressure guage on the truck. You should be seeing 50-60psi at WOT. If you aren't, you've got an issue. I'd bet the high side fuel pump relay needs to be replaced.

 

Where is the relay located?

I forgot to mention that I have a Autometer fuel pressure guage. At idle, I see 37psi, and at WOT, I see 54psi. That has been unchanged from the start. I can see on the fuel pressure guage that something kicks in at 3/4 throttle that immediately adds 10psi.

I have a single Bosch 255lph fuel pump. I would like to go larger, 400-500 lph when I go to the built engine. What about a exterior pump (not in tank). That would make servicing a lot easier.

I have an AEM wideband. I feel confident that it works correctly due to the idle A/F readings are stable and normal (14.6 - 14.7).

 

edited!

 

Anyone?