lean and sputtering with low throttle input

[pSimytSi]

So I've searched many posts for some kind of help but keep ending up empty headed.

I've been having this lean-sputtering problem with my car.. It's happening when I'm staying a steady speed holding a low throttle input. It'll be driving perfect, then instantly it'll start sputtering, my a/f gauge jumps from 14ish to 3 Red - - - meaning it's over 18. It's real similar to what it does when your deceling only you can't accel when this happens.

If I try just letting off the throttle for a second and getting back into it the sputtering just gets louder. The 2 things that cure it for the moment is to engage the clutch and wait for the rpms to drop down to the idle level then resume driving as if it never happend. Or I can downshift and resume driving as if it never happend.

It'll do this randomly a few times every half mile or so if I'm holding steady at say 40mph. When I'm running it hard, even from a stop it has never happened, it pulls hard all the way to the brakes.

I know it has a shorted ISC, a blown Fuel Pressure Solenoid, the stock FPR, FIC 550's, 255lph pump, and a new set of NGK wires and plugs (600miles) they look to be burning pretty good.

Can anyone offer information? I don't have a logger so I can't show any logs. Please help!

 

[Backinajiffy12]

You need a Logger or DSMLINK or AEM. Your cars stock ECU can't compensate for the bigger fuel pump and bigger injectors even though you may have rewired them!

 

[Polyol]

For one you need a ajustable fuel pressure regulator with that 255lph fuel pump.

 

[pSimytSi]

You need a Logger or DSMLINK or AEM. Your cars stock ECU can’t compensate for the bigger fuel pump and bigger injectors even though you may have rewired them!

The ECU/Car has ran great with all it's upgrades sence last spring. This problem has only been around for about a week.

 

[Colt4G63 also]

The ECU/Car has ran great with all it's upgrades sence last spring. This problem has only been around for about a week.

Uh huh. And the shorted ISC doesn't make your ECU blow white smoke either right. Next your going to try to sell us a bridge in NY, or some vacation property in Florida.

Perhaps your long term fuel trims have finally caught up to you. If you're running a cold thermostat, the engine will almost never meet the conditions for the trims to enter "learn" mode. It will have to wait for you to idle long enough to bring the temp up, then try to learn the 150hz and up trims when you start driving, but before the temp goes back below 190 or so. This could take all summer if you run a 160 stat. WOT operation uses a different fuel map that is preset in the Eprom and doesn't change unless you change it with DSMLink or some type of tuning software. I suspect the cruising trims have finally learned a spot they want to be, but that spot doesn't agree with your 150HZ-250hz airflow readings. This is where being able to set your global fuel settings and injector deadtime are crucial.

Corners are vengeful; if you cut them, they will cut you back.