Negative LTFT at Idle, Rich AFR at WOT

Hey everyone,

Tagging: @StreetSpeed6 @Awafrican @Enki

I've been trying to trace an issue with very negative fuel trims at idle, KR at WOT and pig-rich AFR conditions during WOT runs. A lot of these issues started happening after cleaning the intake valves and installing an OCC last March and can be seen in this thread (should you have time): Negative LTFT at Idle, KR at WOT | Mazdaspeeds.org, The New Era in Mazdaspeed, CX-7 & Ecoboost Forums!

Long story short, I took the car to a shop to check for boost and exhaust leaks. Two were found and fixed: first was the EGR (which was deleted) and the second was on the intercooler flange for the BPV and throttle body inlet. Other than that, no other leaks were found and my compression across the cylinders was normal.

I'm working with Stratified on a datalog revision and sent the attached datalogs into them for review. If any of you have time to review the logs to see if anything jumps out at you, I would greatly appreciate it. The biggest issue to note that I can see are the pig-rich AFRs, which go down to 8-9 halfway through each pull in 3rd gear. I've also attached my MAF Cal log and an Idle Log.

If it's not a tune related issue, I'm starting to suspect my primary O2 sensor is the culprit, but they're expensive and I would rather know before throwing money at parts.

Thanks in advance!

Andrew

 

Do you have your secondary O2 sensor? The narrowband exists to calibrate the wideband.


Do these in whatever order suits you:

• Clamp or disconnect and plug the evap line.
  
• With the car idling, if you wiggle the MAF does the idle change?
• Does the issue persist with the filter off (only do this for idle in a relatively clean area and no wind)?
  
• With the car off, disconnect the MAF, start it and log. Does it sound any different? How are trims?
• Pull the intake and inspect it from filter to next post MAF coupler.
• Try a MAF from a known working car.
• Compare your MAFCAL (or idle RPM, massflow and mafv) to another same gen car with the same intake. How far off is it?

Looking at the logs...
For the idle log, I don't really have any context on what 3" intake numbers should look like so to me it just looks like the calibration is off as a best guess.

For the 3rd gear WOT, it looks like you dump 2 degrees (50%) of your timing for no fucking reason right as it goes rich...In my mind it looks like some weird table smoothing issues or something. Who exactly over at strat is tuning your car?

Edit:
Second third gear wot log has identical symptoms...This looks like something might be askew at/sub 2.0 load and/or at/above 4k RPM.

 

@Enki you rock man! Always appreciate your help and detailed replies.

I'll try those suggestions out this weekend. I don't personally know a speed owner, but there are a few in my neighborhood...i might consider knocking on some doors and introduce myself to see if one of them can help me out with a MAF sensor.

I do still have the secondary O2 sensor installed. My understanding is that these sensors can get lazy with age, meaning they're not as fast to react. My idle issue is somewhat intermittent. Sometimes the car is endlessly chasing 14.7 (I.e. 14.0 to 15.0 and back; without AC running). Other times it's pretty stable. NOTE: I know variation is normal, but mine doesn't seem like normal operation to me.

As for the tune, I can't recall who's doing it, but I'll probably switch over to Freek soon.

Hopefully I can get this resolved.

Andrew

 

Two more things to try:

1. If you have the intake out of the car, you should be able to get to the secondary O2 plug (the smaller of the two plugs attached to the bracket on top of the trans). Unplug it and see if things improve. I haven't run one in years because they kept causing me problems.

2. Flash back to an OTS tune if you can get one for your intake. If not, go back to the base map for your mods and see if things change.

 

You ever have your injectors cleaned?

 

Yep...had them cleaned and tested a year ago. Put Overspeed seals in.

@Enki will unplugging the secondary O2 sensor throw any CELs? Also, when I clamp or pull the EVAP line, I assume I clamp or plug (with finger on end) the part of the hose that runs to the intake manifold?

 

Sure will. It will go away a couple starts or cruise after you plug it back in though.

Yeah.

 

So basically, if I unplug the secondary, I'll get a CEL, but ill just be cruising around like that to see if the fuel trim issues resolve. If they resolve, that means my secondary has gone bad?

I assume going WOT would be a no-go with the secondary unplugged?

 

the high negative ltft and the rich afr at boost points towards the car losing air after the maf sensor. It measures the air, then some of it escapes because it's getting less than it expects.

Is your tmic ok? Did it like take a rock through the scoop and get punctured? one of the couplers pop off or crack? If you have a stock tmic throw that on for the lulz and see if anything changes.

If you have your stock intake laying around throw that back on and go to a stock intake tune (like stage 1 or stage 0 or stock). See if the trims still act up. That will tell if it's a tune issue or something else.

 

So @Awafrican had really inspired me to pick up a boost leak tester from Princess Auto (Canadian Harbor Freight), and man...almost every coupler was leaking on the intake to the TIP. It's amazing how tight you really need to clamp those couplers.

But the biggest leak was coming from the rubber valve cover washer seal around the VVT solenoid. I believe Awa also had a leak here in his.

Anyways, I'll need to order up some parts and do the valve cover gasket, VC washer seal for the VVT solenoid and hopefully that will fix most of my issues.

 

Glad you found some leaks sucks that they're there but atleast you have less.

Yup I'm leaking there too awesome, for those looking the vvt solenoid gasket is
Part Number: L3K9102D5A
Supersession(s): L3K9-10-2D5A
"Engine Valve Cover Washer Seal"
https://www.jimellismazdaparts.com/...lve-Cover-Washer-Seal/1889373/L3K9102D5A.html

If you're likee me and the rubber on the VC bolts looks doodoo worth buying some fresh gromets I just ordered some adapted performance dress up kit for it.

 

I really gotta stop assuming people check the simple shit.

Make sure you either reflash or pull the ground and reset the ecu trims before you drive next.

 

He paid a shop to check for boost/ exhaust leaks... @Duey1083 have you had it apart since then?

 

In all fairness to me, I had what I thought was a competent shop look for and fix boost leaks less than a year ago and I hadn't been playing under the hood since then.

I do have a small concern...hoping I didn't fuck anything up, but I forgot to pinch the hose between the intake to the valve cover when doing the boost leak test. Corksport says to pinch this line in order to prevent high crankcase pressures.

Failing to do this, any chance I fucked anything up?

Additionally, their video states that a leak from the VVT solenoid gasket is supposed to he normal?

 

VVT solenoid gasket leak would be because of high crankcase pressures. I'm pretty sure my crankcase pressures while driving are higher than yours were during your test... Don't worry about that unless you start seeing oil leaks or smoking (unlikely on both counts).

 

Related, mine not his vvt solenoid, haven't noticed any oil leak BUT did notice it during boost leak test definitely oil coming out, I did clamp my breather hose although apparently only partially at first, this happened during ~13-15psi, leave it be or replace do you think? That is oil coming out

 

Swap the seal and clean up the vvt solenoid.

 

Was afraid of that, thought perhaps I'd get lucky. Ha. I'll probably just swap the solenoid if I'm in there... thanks

 

Shouldn't be that big of a deal, just need to pull the valve cover and pop the old seal out.