06 LQ4 stock maxing LT&STFT at WOT

[Dominatorstang]

The truck is a stock 2500HD, I had removed the torque management from it months ago since I feel the 4L80E will hold up fine. I also took all the ETC cells to 100% as it felt gutless before.

I discovered today that my Injector pulse widths are going to 26+ms and 114% duty cycle at WOT. This cause is seen by my STFT maxing out to 30.5% and LTFT at 21% and climbing while at WOT.

It starts doing this from about 3500rpm and up but is actually correcting the LTFT when I am below this rpm at WOT, it is like it just switches. I dont see what can cause this and I dont see any KR or other strange inputs.

The only tune changes from stock are on the General tab of Torque management. I even did a compare to another downloaded stock file and do not find any other differences.

I have also tuned the LQ9 that I go done putting in my Jeep YJ in July. The injectors on it never get over 21ms and the LTFT stays solid and the STFT pretty well does too.

Any ideas please?

[Dominatorstang]

In more review of the log compared to my LQ9 log that looks good. I find that this problematic LQ4 shows 255.13g/sec of MAF at 4896rpm but I dont know what to make of this. I just dont see this high of numbers on my LQ9.

Also once it starts dumping the fuel in then my O2's stay very low at about 30 and 43 so I dont think it is correcting a lean condition.

[Dominatorstang]

I dont know much about the CAT over temp protection but this would not be it activating would it?
Update, I tried disabling this and it did not change any thing.

I also went to the stock tune and I still had the same problem.

I then unhooked the MAF sensor and the STFT and LTFT are not maxing out now. The power does feel funny though, like the more throttle I give it then it starts to fall on its face. at this time my STFT are jumping all over and the 02s look like they are switching at WOT with the MAF unhooked. Not sure what to make of it yet though

[Dominatorstang]

I see why it feels like it falls on its face with the MAF unhooked. The timing does the opposite of what my throttle position does. at WOT it is running 5deg and less so the more throttle I give the more the timing drops. this may be due to the fact that it does not know the IAT so it plays it safe. It is not from KR as the most it pulled was -1deg.

I am thinking that I will swap the MAF with the Jeep tomorrow as they both have the same sensor part number but I really think the problem only appears when the MAF signal is sent to the PCM but not a bad MAF signal itself.

Any advice?

[Dominatorstang]

My LTFT numbers were all over the place with the MAF/IAT unhooked so I disabled the MAF in the software and did another log on the way home. The problem is still there, STFT start rising closer to 3000rpm and are maxed at +30.5% by 4200rpm and then the LTFT just keep rising. The last log showed the STFT come up to 30.5% and the LTFT had made it to 14% with a 26.3ms pulse width. The fuel trim cell stayed in the 15 and the dynamic cylinder air made it to 0.81g/cyl. I dont have many other idea's right now.

What would command the system to go rich at WOT in steps, not just a commanded fuel setting but like it slowly adjusts richer but the O2's are already rich and it should not be using them at WOT anyway.

[flame]

If your O2's are reading 30 and 43 then the pcm thinks you are lean low = lean. That is why the STFT and LTFT are correcting trying to add fuel. Typically at WOT your O2's should be in the 800mv range. First thing to check is fuel pressure and volume. Hook a gauge up and verfiy the pressure doesn't drop underload.

[Dominatorstang]

I had that scale backward in my head it looks like. Thank you for correcting that.

I just got done with a more indepth log of this truck vs log of my jeep and I did find another difference that may be explained by the computer correcting for lean condition which I will be checking shortly. The difference I found was the fuel system status, the truck shows CL - Normal when at WOT and the Jeep shows OL - Accel/Decel.

I will put a gauge on it and see what I get, the setup I have is long enough that I can read it when driving so that should help.

Thanks again.

[Dominatorstang]

That is it, fuel pressure goes from 58psi down to 30psi as it revs out. i dont see much pressure change with KOEO vs vacumm with KOER but I am going to change out the fuel filter first and then going after the regulator. When the regulator on the Jeep went bad it started leaking into the intake and making hard hot restarts a problem from flooding. if it is not the filter then the regulator may be plugged up a guess.

Thanks again Flame for correcting me on the mV reading, i got spoiled on my early tuning using the Tweecer as it had a color bar so I didnt try well enough to remember the mV.

Another strange thing is that the Truck was still commanding 14.68AFR at WOT. Well I will work on that after the fuel pressure drop problem if it does not correct it too. Good thing it was still in CL as I was lucky enough running that lean with out blowing a head gasket or worse

[Dominatorstang]

Just for more research before I get the filter and change it tomorrow, I did not find a pressure regulator listed at the parts stores so I am not sure of the system i have until I take a look at mine. Plus my logs from 5 months ago show the same symptoms but not as bad. 5 months ago it would richen up about 35% total and not max out the STFT's, also kept up at the commanded AFR with these settings.

This shows that my problem has got worse or filter has gotten plugged more (I should have seen it on the log 5 months ago though) Now it richens up a total of 50% (tries but maxes out Pulse width in time between cycles) and stops keeping up at about 4000 to the commanded AFR.

This is just more info I wanted to add to help in other peoples different problems they may have. I will update tomorrow with the filter change

[flame]

I'm pretty sure the 06 doesn't have an external filter. Also on the regulator they rarely fail. You need a fuel pump.

[Dominatorstang]

From research, it looks like the filter and regulator a a unit on the fuel pump assembly so I see what you are saying. I did get under my truck just a bit ago and I do have 2 fuel lines headed to the motor so not sure about the regulator but your right that i dont have a fuel filter on the frame rail. That answer why I didnt change the fuel filter when i bought it 6 months ago when i did all the other maintenance and even flushed the trans fluid since it was black. I am guessing the fuel filter in the tank is still what is plugged since it creates plenty of pressure but just cant do the volume. I may see if I can do something with it before i just throw another fuel pump on. May even see if I can throw a fuel filter in the middle of some already quick connects on the feed line and do away with the internal one.

[flame]

I may see if I can do something with it before i just throw another fuel pump on. May even see if I can throw a fuel filter in the middle of some already quick connects on the feed line and do away with the internal one.

If you get rid of the internal filter your pump will likely lock up within a few days. Unless you enjoy pulling down the fuel tank just put a pump in and be done.

[Dominatorstang]

The internal filter is just the same as an external except that it has 3 ports,2 of which are Yed. Them being the fuel pressure regulator and outlet of the filter going out of the tank to the fuel injectors. It was not worth it to me to try and find a reliable way to reconfigure all 3 of these quick connect ports into to one and add an external filter. The pump would still have its sock so the filter after the pump should have no effect on it except to make it try harder to pump when it is clogged up as I am sure the pressure was maxed out on the pump outlet side (probably around 85psi) when I was at WOT but after the pressure drop of the clogged filter restriction then I was only seeing 30psi at the injectors.

I installed the new OEM ACDELCO fuel pump assembly and swapped out the foglight relay for the fuel pump relay as I do not have fog lights and the fuel pump relay had gotten pretty hot from the extra load of the clogged filter. I then did another data log. The fuel trims are staying good now but it still stays in CL-Normal at WOT. The only time it is not in CL is when it does Decel fuel shut off or if the truck is just started.

My settings all look good so I guess I just need to figure out what parameters puts it into OL at WOT and see what I am missing.

[Dominatorstang]

I am going to make a new post as this is a different problem now and from what I can tell then it goes to OL when the manifold absolute Pressure gets somewhere in the mid 80s or higher. It should also go into Power Enrich OL mode by my stock settings of about 90% or more TPS.

Thanks for your help Flame