Help with fuel trims, log included.

Wondering if you guys have any thoughts about this situation. Log is attached.

Recently installed a Damond PCV plate, new PCV, stage one catch can, and oil fill breather cap. Other mods are minimal, Cobb intake, balance shaft delete, mild tune from versatune, stock K04, larger turbo inlet, EGR delete w/EGR pipe removal.

This morning I disconnected the battery, took off the (OEM) MAF and cleaned it thoroughly, cleaned the electrical connections there and they all looked fine. Left the battery disconnected for about 90 minutes, came back and hooked everything up, let it idle until it was completely warm and then pulled these logs out of it.

I'm wondering if I have a bad O2 sensor or something? Why is my STFT pegged at 25, and my LTFT never comes off of zero? You'll see my STFT change just a hair when I blip the throttle, otherwise it is always stuck at 25 and even when I blip the throttle my LTFT doesn't change at all.

Air fuel ratios look good, but I had a P2188 pop up so I am trying to chase that down.

Thanks for any advice!

 

You should be logging quite a few more things than you are. Actual AFR, Calulated load, throttle pedal position, wastegate duty cycle, injector duty cycle, etc.

Did this just start happening when you installed the new parts? It sounds like you probably have a checkvalve in the wrong direction or a hose hooked up the wrong way. LTFT is just an average of STFT after an amount of time at a given load, so if you drove around for a while eventually your crazy STFT trims will move over to LTFT. That'll reset every time you flash. I can't really see what you're doing during this log since you don't have any information about where throttle is and where your calculated load is at.

 

Maybe check the oring / gasket on the MAF sensor.

Something doesn't seem right with sitting at just 2-3 g/s on idle.

EDIT: agreed on the parameters you are logging with. Also, do you need to tune for the oil breather cap? You may need to...

 

@VashEXE sounds good, I'll log all of that other stuff and anything else that looks semi-relevant. Is it good if I just leave it at idle in my parking spot while I log stuff? Or would logs of actual driving around the city be more beneficial?

Everything is certainly hooked up properly, I just finished a full engine rebuild, so I for sure know my way around the engine. When I did the PCV plate/PCV/catch can I pulled off the intake entirely and really took my time with everything.

A few days ago I did a round trip drive around...180-200 miles in total. Most of it was highway driving, CEL never popped up until after I had finished the majority of that drive and did about 4 miles on surface streets back to my house.

@Duey1083 good call, didn't think about tuning with the breather cap installed. I definitely did the previous tune before I installed these new parts.

Hopefully you guys can forgive my ignorance, I am for sure an amateur and this is all a bigtime learning experience for me!!

 

@liquidefex, I just asked the guys on Shoutbox (also, cause I'm interested in getting a vented breather cap as well).

Does the one you installed have a check valve? If it does not, you're going to be introducing unmetered air and your trims will be all over the place.

 

If this log was done at idle you have a huge vacuum leak. You should check what your Actual AFR is showing because basically, if you're maxing out STFT trying to stay at 14.8 (stoichiometric at idle) you're probably not even at 14.8, which means a shitload of air is getting in and it's adding a bunch of fuel to compensate. If you're just dead locked at some Actual AFR value that's could be a bad 02 sensor, but that is the most misdiagnosed part in tuning honestly. I'd check everything else first before doing that.

I ran a vented breather for a long time. Remember, that isn't attached to the intake tract, it's in the crank case. You'll still get a little unmetered air, but not enough to max out STFTs like this. This seems like there is something completely loose/unconnected on the intake side honestly. Does the car even run well in it's current state @liquidefex ?

 

@Duey1083 yeah it has a check valve in it, it is https://www.c-f-m.com/performancepa...-Kit-for-1986-2001-Mustang-GT-Cobra-p3206.htm because I have an 09.

@VashEXE that first log was done at idle, this log I just did looks very very different, and also a P2187 popped up while I was just idling it and logging this info. In all honesty the car is running quite well, some stuttering/hesitation on aggressive acceleration, but got about 30mpg on that 190ish mile road trip I did the other day. Also I can't hear any vacuum leaks anywhere!

Check out these new logs, this is everything I could see as relevant using versatune to log it all.

PS I watch a car wizard video last night.



If you go to 14:15 he starts talking about the MAF flow volume, and this seems to be happening with me. If you look at the I column in the log it starts out under 2.3 and gets progressively lower and lower. Could it be as simple as a failing MAF sensor causing weird Air/Fuel ratio stuff so it throws a P2187 or P2188 at different times?

@Duey1083 Also checked that MAF o-ring when I had it apart earlier today, ring is still malleable/no cracks or tears in it, still looks good in my opinion.

 

The valve cover has a breather to the intake, unless OP blocked it off.

I was trying to figure out how the breather cap could cause this. Of course, this isn't the issue since his has the check valve.

I agree with you...his MAF is barely registering anything. So I think you're on the right track.

EDIT: @liquidefex, how did you clean your MAF sensor? Maybe you caused some damage?

 

@Duey1083 I do not have it blocked off, that breather is still running to the intake. I think I'm gonna see if I can pull some voltage data from my O2 sensors to make sure they are signaling how they should be, but yeah I am leaning towards this MAF getting wonky.

Cleaned the MAF only by spraying it repeatedly with MAF sensor cleaner, didn't wipe it off or use any other cleaning chemicals on it.

 

Well I figured again I would try to bring some closure to this thread.

And I wanted to thank you all for dealing with me, a genuinely stupid, stupid idiot.

Would anyone care to place a wager on why my fuel trims were so weird? I ordered a new MAF sensor and I was going to install it just a little bit ago, when I noticed this!




So now that is all buttoned up, I'll hang onto the new MAF sensor for a week or two to see if that sensor is still weird, but somehow I doubt that is going to be the case...

Anyways, thank you guys for all of your time and thoughts!

@VashEXE
@Duey1083

 

Is that your recirc tube or valve cover breather that's disconnected?

That'll do it! Haha...glad you figured it out

 

Hahaha yeah its the valve cover to intake recirculation tube. Gonna take it for a couple mile test drive right now and see how it feels, hopefully that CEL stays off and the rich/lean stuff sorts itself out.

 

Leak, pre turbo, called it haha. Glad you found it.

 

Hey man did your stft and ltft improved after this?

 

This was fun to read, great plot twist!