Need help diagnosing 29DC: Cyl Inj Cutout Code?

[IQraceworks]

I was on the way home from work today...just cruising on the highway at 70mph. I just barely rolled into the throttle a little bit to get in front of a car before I changed lanes, and it instantly felt like the car started shaking and running rough. No check engine light, but something felt off. I ended up clicking it down into 5th to get the vibration to calm down a bit. I figured my center bearing on the driveshaft failed, or a u-joint. I limped the car home as easy as I could. I did notice that when I rolled onto the throttle the motor had no power at all.

When I pulled in the driveway....the car was idling like it was only running on 4 or 5 cylinders. I shut the car off, and then fired it back up....instantly, everything was back to normal. I scanned for codes and have a 29DC injection cutout, 2C77 O2 sensor after cat, and 2C78 O2 sensor 2 after cat). LPFP was right at 72psi at idle, and HPFP was around 700 at idle.

So.....did I have an injector die, and then come back to life after I restarted the car? Since the O2 sensors triggered a fault...may there was a rich or lean mixture? Could an injector have gotten stuck open? Faulty LPFP sensor?

I'm running a Walbro 450 LPFP, and when I did a WOT 3rd gear log a few weeks ago, the HPFP looked to be in great shape. My plugs and coils are new with only around 8,000 miles on them.

Any ideas would be a big help!! Thanks!!

 

[IQraceworks]

Well, I was able to get a log! I fired up the car this morning while I had MHD running and was able to log everything. As you can see, LPFP and HPFP pressures look fine, but as I went for a drive, as soon as I start rolling onto the throttle....and the HPFP pressure starts to climb up to around 2,600psi.....and then just falls on it's face.....down to 422psi. Then it triggered the 29DC injector cutout faults again, and I had to limp it home. Once home I shut if off, started it back up...and all was morning again.

When a HPFP goes bad.....is that how they act? They build pressure just fine....and then just crash?

Here is the log...sorry, it's kind of long...

datazap.me | Iqraceworks | Log 1631469618

datazap.me

 

[NoGuru]

I did not see LTFT in the log but your STFT is climbing fast. I'm no tuner but I would say the three things to look into would be O2 sensors, Fuel injector, and maybe HPFP.

Who is your tuner?
What index are your injectors?

I would be VERY careful with the car until you resolve this and do not drive it unless you have to.

 

[IQraceworks]

I'm pretty sure that the reason the fuel trims are climbing, is because the HPFP/rail pressure is dropping....at one point I'm at full throttle and the rail pressure dropped down to 460psi. I don't see how injectors would have anything to do with it.......or O2 sensors. Neither one of those things would make the rail pressure fall off like that.

I'm running a pretty mild 93 tune that V8Bait made for me. I've been running it for several days with no issues.....3rd gear logs looked great and the HPFP pressure never got below 2,300psi........then the next thing I know I'm driving down the highway, HPFP tanks, and I get the 29DC injector cutoff code.

Is there a seal or high pressure relief in the HPFP that could be failing when the pressure climbs??

I'm 99.9% sure this isn't a tune issue...

 

[wheela]

Sorry, i'm on my phone and the datazap site isn't cooperating well. What happens with your low pressure when the high pressure tanks? I see you have the walbro 459, do you still have a stock EKP module running it? I've read those can overheat running larger lpfp. Perhaps that unit is failing causing a dip in low pressure, causing your hpfp to loose pressure? If that was happening, i'm not sure why high pressure wouldn't recover once your low pressure does though. Maybe the hpfp stays low after the event as some kind of limp mode? I've seen others post similar problems when their EKP was going out due to larger lpfp, so may be worth checking out. However, i'm n55 and still on a stock lpfp, so perhaps others with direct experience could chime in?

 

[IQraceworks]

The LPFP pressure looks fine....I don't think it's that. I did notice on my log that when the HPFP died off, both the STFT's maxed out on both bank.....so it wasn't a stuck open fuel injector. If that was the case, one bank would be overly rich.

At this point..... everything is pointing to a bad HPFP. It's like the HPFP builds pressure just fine to a certain point......around 2,4-2,600 psi.....and then it just tanks. I know there is a fuel pressure control module inside the HPFP.....could there be a faulty seal on that thing that fails at a certain psi??

I just don't see anything on the log that points to an injector problem.

 

[IQraceworks]

So...I went out tonight after work and tried to get a nice clean log showing what's going on. I slowly rolled onto the throttle in 3rd gear.

As I'm rolling into the gas in 3rd gear, at around 3,000rpms with only 4psi of boost the HPDP pressure just tanked...it dropped from around 1,200psi down to 215psi. As soon as I let off the throttle, it bounced back up to 2,800rpms.

Both banks STFT jumped up to 34% (trying to correct a lean condition). If this was a stuck injector, I don't think both banks would be equal...one would be way rich or way lean....right?

At this point........I'm pretty sure it's a HPFP issue. What am I missing here?

datazap.me | Iqraceworks | 3rd gear HPFP issues. 93 Base Tune

datazap.me

 

[NoGuru]

At this point........I'm pretty sure it's a HPFP issue. What am I missing here?

datazap.me | Iqraceworks | 3rd gear HPFP issues. 93 Base Tune

datazap.me

You are missing a new HPFP.

 

[IQraceworks]

FCP Euro here I come....

 

[IQraceworks]

Well....I gave it one more shot before I ordered a new HPFP. First, I checked all the plugs after the car sat all day...all dry and look fine (no leaky injectors). Then I hooked up MHD, got a log running, and fired up the car.

This time the HPFP never got above 50psi...the motor sputtered and coughed as it attempted to idle. After doing that for around 10 seconds, the HPFP came to life and the pressure sprung up to around 2,600psi and the motor started to idle normal.

At this point....I'm 110% sure it's a HPFP problem. I think something is jacked up with the built in fuel pressure regulator. I'm going to order a new one off of FCP Euro tonight, along with a new rail pressure sensor.

I will report back after the parts show up and I get to take the car for a test drive.

datazap.me | Iqraceworks | No HPFP at Idle....

datazap.me