slash128

After a couple weeks of researching and troubleshooting I am reaching out to the forum. I have read many threads, gone through the FSM and other docs, replaced parts, logged, worked with friends, etc., still I have resisted starting a new thread, but since the threads I have researched so far have not helped with my issue here I am.

Here is the problem. A few weeks ago I tried fitting my turblown kit, again, but still had issues, so I took it back off. That's a separate soap opera with it's own thread if you are bored... After putting things back together the car started to hesitate and buck and run lean at high RPM. I had this same problem earlier this year when I had done some work prepping for the first install attempts of the turbo, but it eventually went away on it's own. This time the problem is persisting and I am wondering if something was damaged to the point of causing intermittent issues previously, but now whatever it is has finally failed completely. I've read the threads about the SSV, about vacuum leaks, injector wiring, fuel delivery, MAF cleaning, etc. Instead of making a long thread of all the research I have done I will summarize with symptoms and what I have tried to date. Perhaps I have missed something very simple and can't see the forest for the trees.

Mods when the problem started:

1) BHR coils with dwell increased to 5ms
2) AP crank pulley
3) MS CAI
4) MS catback
5) AP catless midpipe
6) Rear O2 sensor replaced with Bosch wideband for AFR gauge, DTC P0037 masked
7) Air pump deleted, pipe to exhaust manifold removed, block-off plate and gasket on airpump port on exhaust manifold, 60A fuse removed, DTC P0410 and P0411 masked
8) Boost gauge

Symptoms:

1) If I rev the engine while parked and let go of the pedal the AFR will hunt between low17s and high 16s for several seconds (5-10 sec) before settling back down to 14.7 with STFT idle high, typically around 25%

2) While driving and accelerating thru low to midrange RPM (5K or so) AFR is normal

3) Continuing to accelerate into higher RPM (above 5-6K RPM) the car will hesitate and buck and AFR will climb, I have logged into 18's

4) The transition from stable engine behavior and normal AFR to hesitation/bucking/high AFR seems to coincide with the transition between closed loop and open loop, based on STFT dropping to 0.

One of two things appears to be happening in open loop with no feedback for the ECU to correct: excess air is making it's way in, post MAF, or not enough fuel is being delivered.

Here is the troubleshooting I have done so far. I try to make a single change at a time so I can keep track of what specific change made a difference.

1) When reverting back to stock I removed my uncapped yellows (all 4) and installed a brand new set of OEM yellows. The problem happened with both the new OEM yellow injectors and with the uncapped yellows. I did adjust the injector scale accordingly. I used the same scaling that had worked previously. I quadruple checked injector wiring and had others verify - no change
2) Cleaned SSV, even though it has very free travel, no stickiness whatsoever - no change
3) Cleaned MAF - no change
4) Replaced MAF - no change
5) Replaced all UIM gaskets - no change
6) Swapped out BHR coils for a brand new set of stock coils and wires and went back to stock dwell timing - no change
7) Checked plugs - they were replaced new a couple months ago and still look good
8) Replaced entire fuel pump assembly (had a Walbro 255lph installed in the original assembly) with complete new OEM assembly - no change
9) Swapped back from AP crank pulley to stock pulley with brake pedal reset - no change
10) Had intake manifold smoke leak tested, no leaks found
11) Removed and replaced the block off plate and gasket covering the airpump port on the exhaust manifold - no change
11) Put uncapped yellow injectors back in (all 4) and scaled as they worked before - no change. I am not going to claim that my scale is perfect, but if my scale is the culprit then I would expect some deviation, but symptoms are identical between stock injectors on stock tune vs uncapped injectors with scaled tune.

What I finally did yesterday was scale the uncapped yellow injectors (all 4) down so the ECU thinks they are smaller, which effectively injects more fuel. I did some logging and tweaking with the injector scaling, leaving all other tables stock. Currently the yellows are scaled down by 75% of what had worked previously (700 vs 930 in ATR Bank 2 & 3 fields). This has bandaided the issue. The buck and hesitation is gone. AFR in open loop areas is back to normal. Now before someone says "ah-ha! there it is!" remember that the stock injector scale (in fact, entire stock tune) with new OEM injectors exhibits the same hesitation/bucking/lean AFR.

I never physically touched the reds but I also scaled them down to correct the high STFT and AFR hunting at idle. Currently they are at 88% of the stock table value (325 vs 369 in ATR Bank 1 field). Since all 6 injectors seem to be affected this brought to mind some questions. Could the injector driver circuitry or ECU have a problem? Is there a way to test? Battery and generator voltage seem good, but I don't have an Ammeter capable of performing the high load tests. Even still, I thought the injector latency/battery voltage table should correct for low voltage.

Thanks in advance for any help. This has been driving me nuts...

dannobre

iTrader: (3)

What map are you running on the AP?

I had a corrupt map once that did something similar

Do you have any other CEL's killed by the AP?

ESS..did you check it? Swap it out with another one if you can get one?

slash128

The current map I am running is the stock map, except for the following:

DTCs masked: P0037, P0410, P0411
Injector Bank 1 value currently at 325
Injector Bank 2 & 3 value currently at 700

I have tried several saving, recreating and reflashing the map but symptoms persist. However, by tweaking the injector scaling the problem goes away. Based on this my thought is the map is not corrupted, but good thing to verify.

I have not gotten any other CEL's. One thing I was curious about is that others seem to get a lean code 2096. I have not seen this, even though both the AP and Bosch read nearly identical high AFR. Only thing I came up with is possibly that the lean code gets thrown from the rear O2 sensor, which I have deleted. Can anyone verify if this is correct or incorrect? I have come across documentation that seems to indicate that the rear O2 sensor is involved in the feedback to a degree. Perhaps this is the root cause of my issue? Anyone else have issues after removing the rear O2 sensor? FWIW, however, I had been running fine without the rear O2 sensor since last fall, so I didn't think this would be the culprit.

I did wipe off the ESS and it looks pretty clean, but I have not swapped it to test if it is faulty. I will add that to my list of things to try next. Thanks for the advice.

dannobre

iTrader: (3)

You can get lean looking spikes with a missfire too....basically if the ignition missfires it sends the high o2 mixture into the pipe.....so it looks lean....

What are your A/F like just before it starts doing it?

slash128

Just before it happens A/F is normal, compared to what is in the fuel tables for the given load & RPM. It is a very sudden change. It doesn't spike and come down, it just keeps climbing as long as I dare keep my foot on the gas.

slash128

So in a last ditch effort I went back to stock to take to the dealer. After uninstalling the Cobb AP the problem was still there at first, but then went away after about 10-15 minutes of driving. Not even enough time to get to the dealer. I reinstalled the Cobb with the Stock Style map and the problem came back and stayed. I re-downloaded all the Cobb maps and tried again, problem persisted. I uninstalled the Cobb again, problem was gone after another 10-15 minutes of driving. Not sure what it's going on, but at least I know it's not the car, and that I can correct the issue by scaling down the injectors in ATR if I want to use the AP.

slash128

Problem fixed. Hope this helps someone else. Turned out to be that one of the MAF screens, the one right before the MAF, had gotten dislodged and turned sideways so it was edge on facing the MAF sensor. Not sure why uninstalling the AP had any effect. Maybe the flash on the ECU was able to compensate more than the ATR stock map. I dunno, but problem solved

EricB

iTrader: (7)

this happened to me a few days ago.. along with...

#1,4 wires were not fully seated on the coils
maf gasket was broken
screen was turned sideways

hard launch, then at 20mph the car bogged like no other. lost all its power and idle dropped to 0. when i restarted it the car only stayed on for 3 seconds.