Need Some Help Diagnosing a Problem - Starts misfiring/leaning out when hot

[CJ_]

Alright guys so I need some help with diagnosing this problem. First of all, huge thanks to Brad (Corradovolksb) for all your help and with tuning so far. As some of you know I finished putting my motor and transmission in last Thursday. I was having some problems getting into boost and was working through some tuning with Brad. He realized I was tuned for a HPX maf and after we fixed that, the car was running great. It was a little lean under boost, but anyways I decided to drive it out to Vegas for Wüste. I was babying it most of the way, but had no problems hitting 15-16 psi of boost. The ambient temp was about 70º when we left.

About 2.5 hours in to the drive, it started leaning out under throttle and began misfiring. We were about 20 miles out so we pulled over for a few minutes to check things out. After shutting it off, it wouldn't start back up, it would kick for a second and then shut off. We let it cool down for almost 2 hours (the ambient temp was above 100º at this point). It started back up and ran fine again. We got back on the road, and it did the same thing, this time about 2 miles from Wüste. luckily my friend had AAA and I was able to get a free tow to the event. At the event, some of the guys were helping me with some diag and it was misfiring mostly on bank 2 (cyl 4,5,6) at idle with 5 and 6 being the worst.

Then on Sunday, I started it up and idled good, ran good, AFR looked alright at ~15 so I decided to give it a shot home. We got about 1.5 hours into the drive and same thing happened. Ended up getting a u-haul in Kingman and towed it the rest of the way home.

Summary: for those of you who don't want to read the above

Car runs fine when cooled down, then starts misfiring and running lean when the engine is warm and running for awhile. First happened when ambient temp was about 100º, was driving for 2.5 hours in sub 100º temps. When warm misfires on bank 2 the worst when idling. Starts and runs fine when cooled all the way back down

Heres a list of codes I've noted, in no particular order. Can't remember exactly when what codes where thrown at what times Ill add some as more come to mind

16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean

16558/P0174 - System Too Lean, Bank 2

17965/P1557/005463 - Charge Pressure Control: Positive Deviation

16534/P0150 - Oxygen (Lambda) Sensor B2 S1: Malfunction in Circuit

16514/P0130/000304 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit

17649/P1241 - Fuel Injector for Cylinder 5 (N83): Open Circuit

17645/P1237 - Fuel Injector for Cylinder 1 (N30): Open Circuit

16684/P0300/000768 - Random/Multiple Cylinder Misfire Detected

Misfires on cylinders across the board

These are all the codes I can remember for now

Stuff Ive tried:

Swapping injector adapters -> problem still stays on injector 1 and 5

Swapping coil packs for new ones (thanks MetalMan) -> No change

unplugging maf -> No noticeable change

untucked harness wires from under intake manifold -> No change

New o2 sensor on bank 1 before problem started happening

Swapped ICM deletes -> no change

Checked grounds and voltage at ends of injector adapters

Swapped FP relay for known working one when misfiring -> no change

Swap injector 5 with inj 6 -> open circuit fault moved to cylinder 6

Compression test:

Cyl	Pressure (PSI)
1	132
2	140
3	140
4	140
5	135
6	135

If anyone has any ideas or help is greatly appreciated. Im going to boost leak test it hopefully tomorrow

[Believer]

Have you checked your grounds? Not sure on the S4 but the A4 has a large post behind/above the coolant reservoir and down on the passenger frame rail. Might be more

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[88ninety9]

Have you checked resistance at the injectors?

[julex]

I've had the same problem with HPX, it lacks proper temp compensation unlike stock mafs. I don't have this problem anymore after adjusting tune to allow more % on trims and also adjusting 02 sensor failure voltage thresholds so that fake O2 codes don't pop up when car operates in extended lean condition until LTFTs catch up...

[julex]

To elaborate on order of events:

Intake temps get into 50-60C during summer
HPX lacks temp compensation. It under reports true maf flow. Mixture goes lean.
ECU sees that and tries to compensate but hits the 10% LTFT coded limit in software. Car is still lean.
ECU pops a code for "System too lean"
O2 sensor diagnostic subroutine sees O2 sensor voltage permanently stuck under diagnostic threshold (I think it was 0.02V) and pops a generic "malfunction" code since it is neither short or open as voltage sits at something like 0.01V
Car goes leaner and leaner and thus hotter and hotter... with various level of problems. In my case it was moderate lean, in yours severe lean so that it wasn't firing mixture anymore.

[gmdiluca]

Sounds like Julex is onto something except I'm pretty sure OP is running a Hitachi or Bosch because he said he was mistakenly tuned for an HPX but later fixed that?


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[christianb5s4]

Luca, he's running an HPX maf AFAIK. CJ feel free to chime in on this one, but Julex could definitely be onto something.

[CJ_]

Sounds like Julex is onto something except I'm pretty sure OP is running a Hitachi or Bosch because he said he was mistakenly tuned for an HPX but later fixed that?

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Yes this is correct. I'm running a hitachi maf. Daz had me set up for a hpx maf in my base file because I talked about an hpx with him, but never ended up going that route. After corrado changed the maf values to hitachi, that's when it started running better.

[CJ_]

Also I forgot to add, I did check the grounds and I checked voltage at the injectors and that checked out okay.

[erykv1]

what ignition system are you running? factory or 2.0T?

[CJ_]

It's the ECS 2.0t conversion, forgot we tried swapping ICM deletes and the misfires did not swap banks

[erykv1]

It's the ECS 2.0t conversion, forgot we tried swapping ICM deletes and the misfires did not swap banks

make sure those ICM deletes are on tight, I know there were a handful of reports of bad connections between the ICM deletes which is why I recommend people to solder. Might not be your issue but cant hurt to double check.

[CJ_]

Have you checked resistance at the injectors?

I just checked the resistance at the injectors and this was the results:

Injector	Resistance (ohm)
1	16.0
2	15.6
3	15.3
4	15.2
5	25.5
6	15.5

Could this be part of the problem? 1 and 5 is where I'm getting the open circuit injectors where 5 happens the most. 5 obviously seems way out of spec, 1 is closer which could explain why that code doesn't come up as often

[vavJETTAw36]

I just checked the resistance at the injectors and this was the results:

Injector	Resistance (ohm)
1	16.0
2	15.6
3	15.3
4	15.2
5	25.5
6	15.5

Could this be part of the problem? 1 and 5 is where I'm getting the open circuit injectors where 5 happens the most. 5 obviously seems way out of spec, 1 is closer which could explain why that code doesn't come up as often

Swap injector locations. That's what I would do. It's pretty easy to pull the fuel rail. Just note you'll probably need new seals. I'd put them on just to be safe.


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[88ninety9]

^seems this is the best next step. If it doesn't follow I'd start tracing wiring.

[CJ_]

Yep so I swapped injector 5 and 6 and the open circuit moved to cyl 6.

[vavJETTAw36]

Yep so I swapped injector 5 and 6 and the open circuit moved to cyl 6.

Boom. Glad you found something resembling an issue. Now fingers crossed that it keeps all the other codes from cascading.

Just curious what injectors you use?


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[BLK01S4]

I've had the same problem with HPX, it lacks proper temp compensation unlike stock mafs. I don't have this problem anymore after adjusting tune to allow more % on trims and also adjusting 02 sensor failure voltage thresholds so that fake O2 codes don't pop up when car operates in extended lean condition until LTFTs catch up...

Thats interesting, I run an HPX myself. Could you reference where those changes could be made ??

[MetalMan]

I just checked the resistance at the injectors and this was the results:

Injector	Resistance (ohm)
1	16.0
2	15.6
3	15.3
4	15.2
5	25.5
6	15.5

Could this be part of the problem? 1 and 5 is where I'm getting the open circuit injectors where 5 happens the most. 5 obviously seems way out of spec, 1 is closer which could explain why that code doesn't come up as often

Interesting... if the ECU doesn't see a low enough impedance that seems likely to cause an open circuit fault.
Where did you buy the injectors? Might be worth asking them if there's anything they can do. (unless it was Daz... RIP)

[CJ_]

Unfortunately, I did get them through Daz. They were Bosch EV14 630cc at 3bar. Luckily I found them on eBay for $35 each. Im going to swap #5 (now #6) and #1 just to be safe.

That kind of makes sense that it would happen worse when hot because the resistance should go up as they get hot correct? meaning they would be less likely recognized by the ecm

[vavJETTAw36]

Unfortunately, I did get them through Daz. They were Bosch EV14 630cc at 3bar. Luckily I found them on eBay for $35 each. Im going to swap #5 (now #6) and #1 just to be safe.

That kind of makes sense that it would happen worse when hot because the resistance should go up as they get hot correct? meaning they would be less likely recognized by the ecm

Make sure they are genuine. There are a lot of aftermarket units out there the don't flow worth crap (YouTube it). Just look for the Bosch stamp.


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[CJ_]

These are them. If anyone has any input on genuine or not, let me know. They look pretty genuine to me

http://m.ebay.com/itm/Bosch-EV14-60l...ATCHING_ACTIVE

[vavJETTAw36]

These are them. If anyone has any input on genuine or not, let me know. They look pretty genuine to me

http://m.ebay.com/itm/Bosch-EV14-60l...ATCHING_ACTIVE

Description and brand says genuine Bosch. You're good.


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[BLK01S4]

don't forget to order OEM O-rings too. Had to swap the green ones out.

[CJ_]

^ are the blue ones good? cause I have a bunch of those left over from when I swapped all the rings for OEM when I first installed them

[BLK01S4]

all I know is the green ones leak and I smell gas when running. OEM rubber o-rings stopped the smell. IIRC the blue ones go on top of the injectors not sure if they are the same OD/ID as the stock OEM o-rings.

EDIT** https://jhmotorsports.com/shop/catal...h=21_56_61_240

[CJ_]

Umm so I went to start it yesterday afternoon and the oil light was flashing. Went to check the oil and it took a whole quart! No leaks underneath and haven't seen any smoke out the exhaust. Anyone know where it could be going??

[88ninety9]

When is the last time you checked the oil level? May want to check your intercoolers...

[erykv1]

x2 on checking intercoolers. seals could be bad on the turbos (doubtful since they are new)... but oil just doesn't dissapear.

[christianb5s4]

Those injectors are right but make sure they are the correct length aka the same as the rest of yours.

[CJ_]

If the seals on the turbos went bad, wouldn't it be smoking a ton? Would it be smoking if I was consuming it in the engine?

[vavJETTAw36]

If the seals on the turbos went bad, wouldn't it be smoking a ton? Would it be smoking if I was consuming it in the engine?

Maybe its sitting in your IC's from pcv blowby ;)

[CJ_]

So no signs of oil anywhere in the ICs or IC pipes.. Should mean my turbos are okay correct?

[88ninety9]

Did you top it off or drain the oil? A visual inspection could give more detail as to what's going on. You have

No oil in intercoolers/piping
No smoke
No external leaks

Maybe a head gasket? My best guess was excessive blow by....

[CJ_]

Wait a minute, after some research this is the light that was on: Meaning it was oil pressure?? what causes that light?

I checked the oil and it was a little overfilled now, so maybe I wasn't as low as I thought..

[axnjaksn]

see if there is any codes with vcds, could be your oil level/temp sensor is bad?? or oil pressure sensor? or maybe there is an underlying problem in the wiring harness?? am I in left field with this one?? definitely not the what you want to see in your cluster

[Corradovolksb]

I had this same issue with my buddy's s4 and I found the wire between the pressure switch to the connector at the drivers front of the intake manifold was broken causing the oil light to come on. Check the wire before you dive into checking oil pressure it will save you the headache of pulling the oil pressure switch and installing the oil pressure gauge.

[y3ti]

That's the low oil pressure warning. Not good if it's legitimate... I wouldn't drive it until you know for sure.

[88ninety9]

I had this same issue with my buddy's s4 and I found the wire between the pressure switch to the connector at the drivers front of the intake manifold was broken causing the oil light to come on. Check the wire before you dive into checking oil pressure it will save you the headache of pulling the oil pressure switch and installing the oil pressure gauge.

Good call. With a recent stg3 build that's a good possibility

[CJ_]

Just found these dangling down in the engine bay.. Looks like it leads down by the oil filter, this should be my culprit right?