Cuts out under boost, logs attached

BlackLC2burd

Member
Joined
Jan 8, 2011
Having a problem with boost cutting out under load. Feels like it stalls under a heavy load, loses all boost, but right after I let go of the accelerator rpms come back up. Mods are in my signature. Fuel pressure rises with boost and steady. Turbo is set tuner style at 10 psi (no map signal to powerlogger yet though). Cam sensor end play is set to .015". Pressure tested the intake system from turbo inlet to 30lbs and no leaks what so ever. All vacuum lines zip tied. New oem module and coil, hotwired. New wires from rock auto. NGK ur5s gapped to .28. Grounds are all tight with no voltage drop (several ground bars throughout car hooked directly to b-) I did notice that the o2 does not cross at all. The denso sensor that was in there before did not cross either, so i replaced it with a bosch unit. Same results. 2 bad sensors possible? Also, my blms are real low. I tried lowering fuel pressure to 39 psi and played with the maf translator settings, same results. Im starting to lean towards injectors causing the low blms (115) or some sort of chip/pcm issue. Have not checked for a flat cam, weak valve springs or rubbing crank sensor. Would any of those cause this issue? I would think a bad crank sensor would cause the rpm to drop to 0 if the crank sensor lost signal? Any help would be appreciated. Attached are several logs. Thanks
 

Attachments

  • cutting out1.dat
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  • cutting out2.dat
    51 KB · Views: 64
  • cutting out3.dat
    51 KB · Views: 47
  • cutting out4.dat
    51 KB · Views: 65
During the times you start laying into the throttle a little bit, I notice your injector duty cycle maxes way out and pulse width is through the roof. May want to get more opinions but you should be nowhere near maxing those 50lb injectors out, especially at that low of a load. You're barely cracking 3400k RPM. Oxygen sensor cross counts won't cycle when in power enrichment mode, that's normal.

Couple things that come to mind:

1) Fuel filter
2) Bent/kinked line (notice you have modified feed and return lines....why?)
3) Incorrect injectors/chip combination (may want to verify with Eric)

Capture.JPG
 
The MAF signal goes vertical at these points, check it out on the same area of the same log that 87geeinn shows. The engine gets drowned in fuel.

RemoveBeforeFlight
 
Translator switches On On On Off. Base set at 8, WOT at E.

I will check it out when I get a chance. As for the o2, during the whole 15 minute drive, it never cycled, closed loop or during pe always above 750mv-850mv.

I did notice the idc reach 100%, which does not make sense as o2 was reading rich and ecm is trying to pull fuel. Why the rich command? I will get in touch with eric in regards of the chip.

Thanks guys.
 
As I posted, the MAF signal is the issue. Check the log:

CuttingOut1.jpg


The ECM is reacting to (following) the MAF signal for the main fueling input. Air flow goes up, needs more fuel.

RemoveBeforeFlight
 
RmvBfrFlght,
I meant to comment on the maf earlier but works getting real busy. I did notice that the signal shot straight to 256g/s. Is that not a good thing? For some reason i thought it was ok. Do you have any logs of a good signal? Thanks again.
 
The MAF reported airflow doubled in the blink of an eye. Not good. Here is more along the lines of what I would expect (not my log):

run_3.jpg


RemoveBeforeFlight
 
That actually looks like an extender chip log.

It is possible for the MAF to exceed 255 but it takes boost of > 10-12 psi to do it.
 
Makes sense. When the weather clears up, I'll stick a stock maf on. Would a bad maf spike up? I usually see bad mafs have a low (voltage) or drop outs in the signal. Possible bad calibration (settings) in the maf translator or possibly bad translator? Thanks again guys. Really appreciate the help.

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Found the problem, opened up the convolute on the maf pigtail. While monitoring the signal, reference, and ground with dso on peak detect, I found that twisting and pulling on the ground wire underneath the alternator would cause voltages to drop, losing ground.

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