Looking for some info here on AFR's going lean over night.

So I was out tuning last night on good old CA 91 oct. from the 98 oct I am used to in TX.

So I was able to get my AFR's into 11.5 steady across the band with 100% meth.
Today I get in the car, step on the gas a bit and watch my AFR's cruse up to 16's !!!! With no laptop in the car to log with. So I let off and just cruised the rest of the way.

Has anyone ever seen such a change over night with no tuning from last nights session to todays?
With the 91oct and 100% meth I have been aiming for 11.5 AFR from 140 load up and 12.5 from 0-140 load.

I have never had this happen before and am curious where to start trouble shooting.
BTW I did test the meth pump and its working, plus I can hear it turn on under throttle.

NOTE: I have been messing with my PTE 880's latency lately but they looked good last night.
High trim: -3
Mid trim: 0
Low trim: 0

Thanks for your help.

 

If it leaned out that much I would first make sure your meth kit is still spraying and/or you still have meth in the tank.

If so, then I would look towards the fuel pump or FPR

I had a fuel pump go bad the other day. AFR went from 11.5 to 15.1 at WOT.

 

I added the part about testing the meth pump right when you replayed. Sry hahah.

I am thinking I have a cursed Walbro 255, with out a Fuel Pressure gauge in the car to test with how do I test fuel pressure under boost?

Thanks

 

How did u test the pump though? Did you take out your sprayer and make sure that part is spraying? The pump can work still but if there is a leak or obstruction it might not make it into the car.

 

Another way to check, although not the safest thing to do is, make a straight 91 octane fuel map quick (just richen the hell out of it) and see if you still see too lean AFR. If you do, it is your FP or FPR

 

I took the nozzle off and some foil from the Heet bottle tops must have slipped into my meth tank, then down the line and stopped in the nozzle screen.

I cleaned it out and all is back to normal, well everything but the fact I still miss the 98oct

Thanks for your help Razorlab