Help Please!
 

I need help.... 2012 Stillen SC 370Z w/ A2A.

AFRs are consistently at least +2.0 above normal (cruising around 16-17, sometimes higher)
Startup is extremely bad, to the point of the car stalling out completely (AFRs reading 19-20)
Upon acceleration, AFRs will jump to about 15.5-16 and then fall back down to 14.7 while the engine is under some load, but then steady back out well above normal.
Sometimes at stoplights, the AFRs will bottom out (10.0) and the car will seem to bog down unless I rev it to about 1000 RPM and then it holds steady around 13 (1.5 below normal)
One MAF reads anywhere from 1 volt off of the other to right on the money from idle to under medium load, respectively.

Recent changes:
9# pulley installed 3/12, car ran better than with the 8# pulley without a tune revision. (EDIT: Car was daily driven for 5 days following pulley swap with no issues)
Power steering and tranny cooler installed 3/16-3/17, drove to Baker Infiniti in West Ashley (~15 miles), up to Moncks Corner (~30 miles), and back to North Charleston (~15 miles), zero issues
Yard work Sunday = no driving
Monday morning, problems...

Things done so far:
Tuner says look for vacuum leak,
Charleston Performance Solutions gets me in to pressure test the intake piping. Found both MAFs leaking, fixed that issue. Found a coupler with a small leak, didn't fix yet, but does not impact AFRs since it's before MAFs
Pressure tested the vacuum lines to the boost meter, BOV, and Fuel regulator, solid to 25 lbs, no leaks
Tuner sent me a potential electronic fix via remote tune, but no change
Swapped MAF extension cables

Current Thoughts:
Bad harness - Nope
Bad Gas - maybe? tuned on 93, 0.01% chance I accidentally put 87 in it
Vacuum leak - maybe? would have to be post throttle body and not a vacuum line.

Does anyone have any ideas? Thank you so very much in advance!

UPDATE: MAF sensor abnormality that follows the connector. I have the "gen 2" Stillen extensions on order, arriving Saturday. More to follow.

Another update: Replacement harnesses received, verified <.2 ohms per wire, and they are not the problem. Car seems to be getting worse as it will not even idle for more than about 20 seconds now before dying...
Ironically the MAF connection without the extension reads .2V lower on the 5V supply signal than the one with the harness (4.803 compared to 5.038 with battery voltage at 11.6)

Just a thought but you said you went with the 9lb pulley but didn't tune for it? That would be putting more air in and leaning the car out. I'd think I'd be looking at the tune and getting some data logs before chasing mechanical issues

AFRs all checked out during the week of driving done post-install... Even though there would be more air, it would still be accounted for passing through the MAFs

Sounds exactly like a vacuum leak to me. Or maybe the connector to your valve timing got hit while installing pulley. Make sure your engine grounds that connect to the stillen brace are legit too.

You should be running pretty dang lean under wot without a tune from that pulley swap.

The closer I got to WOT, when the car was running semi-safely, the closer my AFRs got to normal. I was at 14ish under medium-heavy load, but I never did WOT. Sebastian sent me a tune rev based on the data that I gave him to try and compensate, but it didn't have any effect on the car...

The second thing I checked was those connectors and they are physically intact and seem fine. Data doesn't show any errors there. The engine is pulling timing and fuel a good bit a good bit. Fuel trims are ~ minus 20-30% and timing is retarded. Pulley install was pain-free and a simple pull of and replace. No banging around or anything like that.

All grounds are tight.

A quick and easy way to check for vac leaks is to spray some brake cleaner around the throttle bodies and down around the intake manifold mate-up. If you hear the car pick up idle at all during this then there is a vac leak there.

This will not detect leaks all of the time but like I said it is a quick way to check if your suspect.

Smoke-tested all the lines, then pressure tested the intake piping up to the manifolds to ~11# with no leaks. I pressure tested all vacuum lines to 25# with no leaks. I can't get the car to even idle for greater than 20 seconds at the moment...

I'm going to revert the car back to my original tune to see if it runs. If not, I may be looking at something major....

With that said, I wouldn't expect something major to manifest the way it did.

Update
 

Siphoned and replaced all of the gas, and then flashed back to revision 1 of my tune. Idle started out bad, but got better. Flashed back to revision 5 (current) and the idle started a little rough, but evened out to normal. Took it around the block for some logs, so we'll see! Thank you guys for the inputs!

I'm honestly not sure if it was bad gas or if warming the car up cleared the issue... Once I get a tune rev from Seb, we'll see...

It seems I have unequal flow through the intake Y-pipe. More to follow...

Have you tried testing if one of the MAF sensors is bad? They are quite sensitive so potential for damage is possible. I hope it was just bad gas but I do not think that would mess with AFR readings. A vacuum leak would make more sense if the car was idling high, sometimes comes with a code too but a code should also be thrown for a bad MAF. hmmmmm.... well, looking forward to this resolution, good luck! :tup: Sounding like it was just bad gas, I'd avoid that gas station if that is the case.

Couple of personal observations & questions mate.

1. Are you on a hybrid MAF/SD tune or SD only? If SD only, MAFs having an issue is far less likely.

1a. If you're on an SD only tune, what MAP sensor are you using and where have you tapped into the intake manifold?

2. Whenever me and Seb tried to do a hybrid tune, it always ended with all sorts of hesitations and idling issues. Going back to SD resolved it.

3. I've never seen good equal flow with the A2A pipe, but like I said earlier, it's kinda a non-issue if you're SD only and nothing wrong with your MAP Sensor setup.

4. A suggestion I could make is what my previous Tuner did earlier on which was to bridge the MAF voltage output to each other. Single cable. Effectively makes the MAF voltage signal identical accross both. A good Tuner should still be able to make it work and if nothing else, it'd be curious to see what effect it may have for you. When I was attempting a hybrid tune, this little trick helped quite a bit.

5. I've even gone so far as to chop up my A2A pipe and add 3 honeycomb air straighteners, before the Y & just before the MAFs. Still never saw equal airflow, the airflow just stabilized, but on average I see approx 45-50% more air flowing past the 'outside' run, to the 'inside' run while under low throttle conditions. Under medium to heavy throttle they quickly even out. It definitely helped while attempting a hybrid tune, but SD still won for 'around-town' drivability. The difficulty achieving equal flow across the MAFs was a pet peeve of mine from day 1.

6. Long shot, but way early on, I was getting all sorts of sh*t AFR readings from one bank only. Long story short, it turned out the gasket between Intake Manifold & Lower Plenum had a minuscule tear leading into Cylinder 6. I did pressure test as well, but I didn't find it. Anything past the TBs I usually attributed to air leaking into Cylinders and back out the exhaust. Changed the gasket and it was a night & day difference. AFRs were 100% back on point.

MAFs are good, swapping around cables and MAFs showed the flow imbalance.
Gas was good. Completely siphoned and replaced with good gas.

Thank you!

1. On a hybrid tune, talking with Seb about potentially going straight speed density if the flow/MAF issue can't be resolved and significantly impacts the engine performance/safety.

1a. I have the Omni 4-bar sensor recommended by Seb for this application in the stock MAP sensor location, back driver's side of the manifold.

2/3. Looking in to straight speed density.

4. The only issue with that is the running really rich if you send the higher-flow signal to the ecu. Since flow is not balanced, you really need the average flow from both branches for it to be accurate. Could splicing the wires together cause damage since the voltages would not be equal? Once you get into electronics that small, even small voltage irregularities where they are not supposed to be can be bad.

5. I didn't really look into the logs until now since the car seemed to be running fine. The MAF disparity existed even while the car was running fine under previous tunes, which is weird. I'm thinking that maybe the increased airflow from the 9lb pulley and the Si trim impeller may have caused the greater disparity and therefore made the car perform worse?

6. How did you find the tear? I am trying to avoid tearing down if possible... Trust me, I ill not hesitate to do what must be done, I just feel like an air leak happening all of the time would show in the car idling higher or something like that.

Cheers,

The SpecialtyZ MAP sensor is recommended for the the stock a2w Stillen setup. He recommended the Onmni 4-bar for the a2a setup. I may end up tearing it apart this weekend for a looksie if we can't get it locked in.

Thanks!

I'm curious behind his reasoning for the different MAP sensors. I've got both, and he didn't ask me to change over to the other one. Kinda want to try it now, lol.

What’s your fuel pressure? Around 52psi is normal idle I believe. Also the fuel strainer/pickup could be really dirty/clogged.

Fuel pressure is 52 @ idle.

I received my full speed density tune last night and it's a night and day difference! Hopefully that will be good for the long-term.

Thank you all for input!!

Why do you think your car ran OK for a few days after the swap, before the problem? Any ideas on the trigger?

I honestly have no idea. Other than the vacuum line to the BOV and removing the intercooler, literally no other air-carrying lines were even touched... A theory I have is maybe the MAF signal disparity was initially manageable but the addition of the 9lb pulley caused the imbalance to be too big? Maybe?

Even that I could argue you should see problems immediately following the install...

The other theory is that maybe the orientation of the coupling from the intercooler to the intake Y pipe is directing flow differently after removing and replacing the intercooler.

With the a2a setup the turbulence normally present at the stock stillen MAP sensor location goes away. If choosing to run the stillen manifold unmodified, then tapping in between the two throttle bodies is the way to go to get a clean manifold pressure reading with minimal turbulence.

Turbulence as reason make sense. What doesn't is how changing from W2A to A2A affects Turbulence. Air still flows past the same TBs in the same manner, albeit more flow overall. I'd be pretty concerned the characteristics changed so much inside the intake manifold to necessitate a change in MAP location.

I haven’t confirmed it myself but it’s what I recall he told me also. Perhaps someone that has both installed can do a few runs side by side and check the variation in the two different readings.

So you have two Mass Air Flow sensors that meter the air coming into the engine as it flows past them. There is also a Manifold Air Pressure sensor on the back driver's side of the intake manifold (stock or Stillen). With the a2w setup, that heat exchanger is in the way of air entering the intake manifold and getting to the engine. This can cause pressure fluctuations (turbulence) where the stock sensor position is. Moving the sensor to before that heat exchanger (n between the TBs) gives you a more accurate reading of manifold pressure.

With the a2a, that intercooler is not in the way and so the air flows through the TBs into a giant cavern (relatively no turbulence) before entering the engine.

Just my thought on the why, but I am not an expert.

Ahhh, forgot about that piece of crap Intercooler inside. I had erased that terrible thing from memory, lol. This is a fair point.