Intermittent Lean Condition, FML
 

WTF is going on with the 2015-06-07 log? No changes other than minimal auto-tuning between the two. Barely got the car home on the second and luckily I was only warming up the car and not WOT when it went so lean.

96 chassis
03 VVT motor w/ NB2 sensors
Brain built DIYPNP

Car seems to run fine again now, but who knows when this will happen again. Can't drive a ticking time bomb...

ECU issue?
Electrical issue?

Heading out to re-check grounds again now.

If it got worse after autotuning, you need to look at the settings in Tunerstudio for AFR calibration.

VE changes were minimal between the two logs.

Point is I was seeing 18:1 at light load with targets in the 14.7:1 range, then a few days later everything is fine again with no changes.

Do you feel it go lean? Like bucking, runs like crap? You didn't post a whole lot of info for us to go off of.

What wideband? How old? Last time calibrated? Did you wire it as per the directions included with it? Is this problem new or always done this? Fuel system specs? Fuel pump type and age? Injectors?

Sorry, never really know how much to include to avoid TL;DR syndrome.

Heavy bucking on load. Sounds like it's running on 3 cylinders.

Zeitronix ZT-2. Unknown last calibration, but targets and diplayed AFR have never been an issue. Wired correctly. New problem. Fuel system is FIC 650 EV-14s @ 3bar base pressure, hard-wired AEM 320lph in-tank with under 1k miles, stock fuel lines.

If you lost a cylinder it will appear lean because the fuel never burned.

Also looking at your log you are getting negative throttle positions. to the best of my knowledge this should never happen. you need to adjust the sensor or the offsets in the software. (i might be wrong tho)

I cant find a smoking gun with the data provided but i would assume being intermittent that it is a loose wire

Sorry if this doesnt help

Any response is appreciated.

There is no way I lost a cylinder. I did on my last motor and this is definitely not the case here. Car runs fine today, but I only started it up to wiggle around the ECU wiring as a test. No changes though.

I set the low TP value that way because it's the closest to zeroed. The next value up gives +2 at a minimum.

Could be a bad fuel pump, and you're loosing fuel pressure. If you can hook a fuel pressure gauge up and watch it next time this happens, that would rule out the entire fuel system.

I'll look into getting a fuel pressure sensor hooked into the ECU so I can log it. May drop in a new fuel filter while I'm at it to eliminate the variable.

Old thread, I know..
Did you find out what was going on?

Never got to the root issue. It's been one of those situations where it's one thing after the other is fixed, but always intermittent so difficult to narrow down.

Considering a part-out so I may have some nice goodies up for grabs soon.

How long have you been running with a wideband? Ive seen a few reports of widebands going bad tonwhere they will start leaning out(AEM uego ive witnessed) after about 1-1.5 years of use off of gas and 6-12 months running eth