Sudden drop in G/Cyl for no reason

[CK@UPP]

Hey Guys,

Having some issues on a 2010 silverado, turbo, running SD.

Occasionally, while driving (any load) it will feel like it shuts off. Finally got a log of it (Attached, see the end , 02:32:32.749) you can see the g/cyl drop out all of a sudden, timing goes up, fuel shuts off, then it comes back. But MAP doesn't change, and no real hickup in RPM (until after it shuts fuel off), and there is no MAF at all. Nothing else I can see as far as sensors is picking anything up. Any idea what would cause this, or what all sensors are calculated in the G/cyl copulation?

oop.hpl

It's only for a split fraction of a second, but you can feel it REALLY bad when driving. And always right after the knock and burst seem to act up for a few more fractions of a second.

[SSUte01]

Standard OS? I can?t view the log right now but only time ive experienced the same was on a SD E38 with MAF removed and never got to the bottom of it because the car was sold. My next plan was to swap to EnhOS as I chased it as a APP issue for a while.

[lukearmstrong1990]

post file.

you can see PCM is asking for it as the inj pulsewidth falls away

[CK@UPP]

post file.

you can see PCM is asking for it as the inj pulsewidth falls away

The File is attached below.

[CK@UPP]

We are on a 2 Bar OS.

[CK@UPP]

Bump

[Tre-Cool]

You ever find what was causing it? Have come across a car that is doing this exact thing. Inj PW will drop to nothing. which causes a knock event when injector comes back on.

Car is auto & SD with small cam, exhaust only. had same os car's with identical mods not have this happen. so im a bit perplexed on why this is occurring.

kinda feels like ecu is triggering a knock event to check sensors are there. since the engine was pulled for cam work. i don't know if it had this issue before.

[Cringer]

You ever find what was causing it? Have come across a car that is doing this exact thing. Inj PW will drop to nothing. which causes a knock event when injector comes back on.

Car is auto & SD with small cam, exhaust only. had same os car's with identical mods not have this happen. so im a bit perplexed on why this is occurring.

kinda feels like ecu is triggering a knock event to check sensors are there. since the engine was pulled for cam work. i don't know if it had this issue before.

Are you in SD? If so its corruption of the MAP^2 VVE coefficient. It can spike the calc'd VVE to the maximum or minimum.
https://forum.hptuners.com/showthrea...ittent-Stumble

[Tre-Cool]

Yeah. Cheers for that. Probably my fault as i copied the coefficients over from another tune, when i've never done that before. was in a hurry. typically i copy the VE map only, then regenerate the coeffecients.

Doh.

[blindsquirrel]

OP's file doesn't even have the right injector data (along with many many other problems, like PE never comes in ever).

[Cringer]

Yeah. Cheers for that. Probably my fault as i copied the coefficients over from another tune, when i've never done that before. was in a hurry. typically i copy the VE map only, then regenerate the coeffecients.

Doh.

No that is not all the situation. It is a defect with the OS when you go into SD. If you have not failed the MAF then this is NOT your issue.

[Tre-Cool]

Im not using HPT for tuning.

The tune file i used as the base had the maf still enabled. I Typically dial in the VVE, then re-enable the maf. Both cars have same mods, except this one is SD only. which would explain why SD-MAF car never had this issue.

[Cringer]

Im not using HPT for tuning.

The tune file i used as the base had the maf still enabled. I Typically dial in the VVE, then re-enable the maf. Both cars have same mods, except this one is SD only. which would explain why SD-MAF car never had this issue.

HPT or brand E, or whatever, it doesn't matter. The issue is in the ECM for SD.