So I datalog almost every day.
Drive to work and back. (if i go to work)

And I'm just perplexed at some of things I see.
I often will drop into open loop at idle at very low loadcalc's and hit low 10AFR's.
I can't finger out why. I used to think it was something to do with my fuel trims...which it "might" but now I'm not so sure after I fixed my idle fuel trims and have them almost at zero.

Suggestions? During a single datalog, this may happen 5-10 times.
During idle and during cruise conditions etc.

 

What were you doing when this happened? It looks like you were going fast and then just let off the throttle .....Can you post your fuel maps as well?

 

bad 02 sensor?

 

A lot of times, yes it is immediately after I let off the throttle.
One time I am sure it happens is when I drive up my driveway and let off the gas so I can pull into the garage. The car just spits fuel at that point. Really annoying.

My fuel maps. You can see that I made a fruitless attempt to remedy this by leaning out my 10 load values to 15.2

 

explain why you think that?

 

Out of curiosity, what size injectors are you running and how do you have them scaled, meaning both the injector size and voltage latencies?

Eric

 

Factory injectors. No change in injector size or latency.

My mods:
Test pipe and dejon intake

What I've changed in ecuflash:
MAF scaling ( this was an attempt to fix this problem. It was occurring before my attempt)
Fuel table
Ignition table
VVTI map
Boost settings ( using an EBC so I set all my boost settings high)

 

I have no idea what would cause this, but wonder if your dejon intake is screwing up the MAF under vacuum ? Did you have the same issue when you had the stock intake? Have you tried putting the stock airbox back on?

 

Typically if your fuel trims are so far out of range, the car will drop out of closed loop, reset the trims, then attempt to find them again.. This will cycle every so often until the ECU can find trims that require less than 25% correction..

If I run my car in open loop, my low load cells still idle at 13.5-14.5 or so in open loop.. If you drop out of closed loop into a 10.0 AFR or so, it means you have a huge scaling problem, either the MAF is reading artificially high, TPS is reading higher than normal, or the injector scale or latency is way off..

Fuel trims are an offset of the background map (there is some speculation its the low octane map, but I think its whatever map the octane number puts it in) and therefore, you need to force open loop, make adjustments to get your open loop to fit closely to what stoich should be, then your closed loop trims will be fairly close.

You could have a bad O2 sensor that is completely throwing things off, or some other issue.. but I suspect its an adjustment your dealing with now.

 

So that is what I originally thought. That if I adjusted for my MAF scaling that this problem would stop.

However, my fuel trims at idle seem to be very much within acceptable ranges...which is why this is confusing me.

I have disconnected the neg terminal and reset the trims after loading my newly MAF scaled map.

interesting.

 

Was that immediately following a pull?

I get the same thing if I keep the clutch engaged following a pull letting the engine slow the car down with foot off throttle:

load drops to -8
A:F reads like 86 for one moment then dips down to 10 or 9 and stays there until you step on the throttle again
It's just air flowing through the engine, if you do it long enough you can even perform a free air calibration with engine still running

Loog at row 97 and after, I have same thing

 

Maybe it's a neutral thing?
Actually come to think of it, it may be. When I log runs, I pop into neutral after a pull.
And at stop lights, I'm in neutral which is when I generally notice it.

 

how do you guys know if the ECU is in open or closed loop mode?

cheers
dave

 

The easy way to tell is to use one of those hidden flags in the bitmapped requestID's that nobody is sure what it does..

But if you look at the 02 feedback value, if it flatlines (100 if its Evoscan, 0 if its Mitsulogger) its likely in open loop.. There's other indicators too, but thats a glaringly obvious one..

 

I say O2 sensor. Look how your feedback just stays at straight 100 the whole time. This is from a log of mine: