Hey all,



So I've been battling this fueling issue for a while and can't seem to figure it out. Under boost (does not do this while cruising) I'm noticing in my logs that all 4 injectors will suddenly drop by 10-15%, with the AFR following suit by showing lean. This is under full throttle, so the stock computer should be in open loop. my logs show no hickups in the tps signal, or the MAF signal. I have also replaced the ECU and still have this issue. If it were a loose CKP connector I would think the engine speed would show that, maybe the cam sensor? I'm stumped, what do you guys think?



Here is the log:

Injector dip.jpg

 

MAF is maxxed out. Try a GM 3" MAF and scale accordingly based on the size ratio from your stock housing to the 3".

 

The maf is clamped at 4.40v, there are other occurances of this where the maf has not yet reached the clamp value so I'm not convinced that it could be the problem. It has to be something the stock computer is doing, what else can tell it to pull fuel in open loop?

 

I'm still fairly certain your issue is MAF related.

 

This is what I used to do, fighting a piggy back and factory computer trying to learn past the electric confusion. Reset ecu drive for one drive cycle 30 mins various conditions. Then for the crazy part. Unhook both O2 sensors forcing ecu to run in open loop all the time. I ran this way up in to the point I got my megasquirt. it worked for me. Almost exact same issue. obviously your fuel mileage will sux but you shouldnt have a lack of fueling. if so you have another issue. Failing fuel pump possibly. My fight was Unichip and factory ECU. So there is a difference however, Thought id share.

 

Well I did come here for advice so I decided to try out your suggestion. You were 100% correct i8cobra, it was the MAF! I adjusted the clamp value down in increments until I got to 4.20 - and the issue went away! It still seems strange that the computer would remove fuel in the event the MAF sensor gives a high reading, but the results speak for themselves.



as for open loop, I am using the analog output from the FIC to remap the throttle position sensor, sending the ECU a WOT signal whenever the throttle is over 22%. I know it will run a bit rich in part throttle boost but I'm ok with that.

 

I've just seen it many times on NA cars that have been turbo'ed. That's why I usually either go with a GM 3", or convert to speed-density.