2ToNe04

iTrader: (1)

Hello, Im having two issues right now and its keeping me quite unhappy. Tried to fix it my self through forum searching and part buying, but im giving up, and turning to you gear heads.

First Problem: Idle,

So at idle it seems my truck wants to die, and sometimes it does just die. What will happen is that fuel pressure will randomly go up to 100-108 psi, and then drop, sometimes itll stay. Here is a video of what is happening, green gauge is fuel pressure, and it is accurate, it matched the pressure that was being read on the tech 2.
https://*******/kZJzV

Codes off Tech 2:
P018B-Fuel pressure sensor performance
P069E-Fuel Pump Control Module Requested MIL illumination

note this happened just two weeks ago long after tune.

Second problem:

When in WOT, for some reason at 3k rpm it seems to choke out. I then get the multiple misfire cel flashing. When i let off the throttle it goes away. Could the boost be blowing out the spark?

Final conclusion. My tuner is horrible, and i might give up on the truck.

03sierraslt

iTrader: (22)

What's spark plugs are in it and what gap are they? How much boost?

As for fuel, I assume your running the factory pressure control module correct? What fuel pump?

smokeshow

iTrader: (16)

That fuel pressure issue shouldn't be happening if the internal fuel pressure popper valve is still installed. Looks like fuel pressure goes up and you drop below minimum pulse width where the short pulse adder is poorly calibrated, assuming the injectors are of decent quality. The fix depends on how your fuel system is set up. As for the 3000rpm misfire, we would need more information.

03sierraslt

iTrader: (22)

Good point about the min pulse.

What injectors are in this?

2ToNe04

iTrader: (1)

Spark plugs are either NGK TR6/7 and i gapped them to .030 boost is at 5-7 psi


For fuel, i got rid of stock pump, and i have a LPH 450, and correct, I have a factory pressure control module.

60# injectors from on3. Could a clogged injector cause a spike in pressure? Not too sure just throwing ideas out there lol

I can drop the tank today, and check, how would i look for the internal fuel pressure popper valve, excuse my ignorance i dont think ive seen one. I can also get a video of the 3k rpm issue.

Also is there any parameters i can look up on the tech 2 to verify any issues?


Thank you for all the help i greatly appreciate it guys.

03sierraslt

iTrader: (22)

If you are running 7's then tighten the gap, they don't like large gaps. Bring them down to like .022

smokeshow

iTrader: (16)

If you didn't know what you were looking for when you installed the fuel pump, then the valve is still in there. Might be plugged up, or just maxed out. Given that it is a new pump and the FPCM is still installed and functional you may need to get your tooner to turn some ***** in the FPCM calibration, such as maximum pump duty cycle at lower fuel flows. OBD may be running an intrusive diagnostic on the fuel system by commanding high pump duty cycle, expecting it to open the popper valve and max out around 75psia. Since you've got a bigger pump, it could be overpowering the valve and setting the fuel pressure sensor fault.



Set the values in the 5-25g/s rows down to something like 60%. That's a bit of a guess as you really just need to correlate pump duty cycle with fuel flow at 75psia. If the engine fuel flow rate and popper valve max flow are less than the pump can do at a given duty cycle, pressure will rise. I say all of this assuming the diagnostics reference values on that surface are what OBD looks at to test the fuel system. If they look at the global values instead (the other two standalone values), then you're kind of boned. Also, I'd recommend fixing this fuel system issue first. You may find that it and the misfire are related... Good luck.

NoorJ

Get a log of it in hpt, it could be the fuel pressure sensor is on the way out hence the P018B and is sometimes reading low/high for a short period of time

2ToNe04

iTrader: (1)

sorry im a little late on my response ive had some extra work around the base.

Well fellas, all you guys were correct about the issues.

I first went on ebay, and found new oem replacement parts for a steal.

Purchased a fuel pressure sensor and replaced it. Thank you Noorj
This resolved the fuel pressure issue. P018B.

I downloaded an electrical schematics. I looked into what smokeshow said about the FPCM.

Now, ive had a service trailer brake light, so i was diagnosing and chasing this issue for quite sometime. Well i discovered that on some GMT900, NNBS, trucks had an infused module. FTCM, Fuel & Trailer Control Module. So when i read smokeshows reply on the Fuel control module, I then assumed the FTCM might be out.

Purchased a used one on ebay. Didnt need to reprogram it, just installed it. The service trailer brake system message went away. My trailer brakes work now. No fuel issues. No high pressure anymore.

Solved thank you fellas.


Now my next issue and final issue, is that my truck cannot go wide open throttle or into heavy boost without misfiring, its always around 3rd gear 3k rpm. I just replaced my trans with a trans that had 6k miles on it, and checked my trans already by manual shifts and works good.

I am going to check what 03sierraslt said and regap all my spark plugs, maybe itll solve this pesky misfire under boost.

I also noticed now that i have some mutliple mumisfire at idle. Do you guys think my tune is really crap? I might honestly buy Hptuners, and check it out myself. Gonna check for any IC/intake leaks tonight as well.

Note: noticed on the tech2, Tuner tuned out all O2 sensors. Wth?

smokeshow

iTrader: (16)

Not that verifying plug gap isn't a good idea, but try something else first. Use the tech2 and drive to reproduce the 3000rpm misfire. Monitor throttle position and let us know what it does during the misfire.