LB7: Truck feels fast for a short time......

[GMC_2002_Dmax]

Didn't duratothemax have an issue for along time of hitting cutting out fuel quantity at random times also? Wonder if its doing the samething and what he did to fix it

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He did, and I believe he still does. I have encountered many LLY's over the years that suffered from either an 88mm3 or 56mm3 fuel limiting and I have resolved it every time.

FWIW, my truck right now has a dead pedal, mm3 is limited, when cold. it will absolutely not give me response until the truck warms up to approx 170 degrees. If, say, the fuel temperature sensor was unplugged or not reading correctly, would the ECM limit fuel to xx MM3 until the fuel reached a baseline temp? could the same be said for the ECT sensor? Justin's issue doesn't seems like a rail pressure sensor because it is intermittent, the sensor is pretty stout. so what else limits fuel in an lb7? throttle input right? he said he was going to change the pedal, maybe that works....if it doesn't could we safely assume the ECM is just not reading and interpreting the data correctly after a short while?

There are specific reasons why trucks will have problems with regards to fuel limiting, some are sensor related, some are tune related and some have other reasons. I believe Justin has been fighting a simple issue with regards to his truck, through PM's I asked if he was scripting or comparing his tune when he created a new one.

I have seen tunes created with scripts that will exhibit the same issues as the suspect tune, I know he has changed OS's, but any tune compared from or created from the faulty one will have the same problem.

 

[juddski88]

hmm, thanks for raising that point Tony. In my case, the tune was not created from a scripted one, But that may explain why his issue seems to clear up after a reflash?

 

[JustinD]

Gonna try that tune today after work Trent, I do have another FICM to swap out if need be? But it is an 03 FICM are they the same? Hopefully someone will find it???

 

[juddski88]

all the lb7 ficms are the same

 

[JustinD]

Thanks Tim, think its worth a shot?

 

[super diesel]

Can't remember if this has been looked at yet Justin, but maybe the fuel pressure sensor (back of the fuel junction block in the valley) is starting to take a poop. I had an issue many years ago where the wires to the pressure sensor got meted through because they were close to the turbo compressor housing and cause a slight short every now and again when the truck heated up which caused an issue similar to this. Another shot in the dark.

 

[juddski88]

Mike, that sane theory could apply to any of the shielded wires too for that matter- cps ckp rps

 

[JustinD]

Can't remember if this has been looked at yet Justin, but maybe the fuel pressure sensor (back of the fuel junction block in the valley) is starting to take a poop. I had an issue many years ago where the wires to the pressure sensor got meted through because they were close to the turbo compressor housing and cause a slight short every now and again when the truck heated up which caused an issue similar to this. Another shot in the dark.

Thanks I'll take a look there too.

Mike, that sane theory could apply to any of the shielded wires too for that matter- cps ckp rps

Gonna check all of these harnesses.


Thanks guys!!

 

[TrentNell]

He did, and I believe he still does. I have encountered many LLY's over the years that suffered from either an 88mm3 or 56mm3 fuel limiting and I have resolved it every time.



There are specific reasons why trucks will have problems with regards to fuel limiting, some are sensor related, some are tune related and some have other reasons. I believe Justin has been fighting a simple issue with regards to his truck, through PM's I asked if he was scripting or comparing his tune when he created a new one.

I have seen tunes created with scripts that will exhibit the same issues as the suspect tune, I know he has changed OS's, but any tune compared from or created from the faulty one will have the same problem.

I def agree Tony on the potential problem you can run into with scripts , The initial tunes i sent over were not scripted , we have used scripts to be able to try many different OS's with out chewing up a ton of time , but have tried the same tunes with out scripts to rule that out of the equation also , and the tune i sent over yesterday was not scripted either , so some scripts have been used but this issue is not a due to scripting IMOP .

Gonna try that tune today after work Trent, I do have another FICM to swap out if need be? But it is an 03 FICM are they the same? Hopefully someone will find it???

Let me know Justin .

 

[JustinD]

Let me know Justin .

Will do.

 

[JustinD]

So I found a log from 2009 at a truck pull, log shows it limiting until a certain point then it picks up and timing goes to 28.0* max?? Here is the log does this give any better info??

 

[JustinD]

Finally going to try swapping the engine harness and FICM, hope this is it???

 

[JustinD]

I had noticed ever since I changed my alt about 3 years ago my gauge reads about 16v I always just thought it was a fluke with the gauge, I had 2 new batteries put in 2 weeks ago I noticed the battery tray on the passenger side has corrosion on it now??? Could it be that my Autozone alt is over charging and boiling my batteries and causing all my issues????

 

[JRODS*LB7]

I had noticed ever since I changed my alt about 3 years ago my gauge reads about 16v I always just thought it was a fluke with the gauge, I had 2 new batteries put in 2 weeks ago I noticed the battery tray on the passenger side has corrosion on it now??? Could it be that my Autozone alt is over charging and boiling my batteries and causing all my issues????

Sounds possible justin when did you find that out?

 

[JustinD]

I was looking at another 01 truck, and his gauge read more like 14volts and I noticed my battery leaking yesterday. I am going to put a new alt in it after work today.

 

[JRODS*LB7]

I was looking at another 01 truck, and his gauge read more like 14volts and I noticed my battery leaking yesterday. I am going to put a new alt in it after work today.

kool hopefully thats it :thumb:

 

[juddski88]

my truck with one battery and original alternator run at 15.5v after running for a few minutes....no battery problems

 

[JustinD]

my truck with one battery and original alternator run at 15.5v after running for a few minutes....no battery problems

Probably not my issue but I guess I need to fix it regardless.... Still going to have the harness and FICM changed tomorrow.

 

[JustinD]

Well the engine harness got swapped today, gonna go pick it up after work and log it to see if it is behaving now??? It was done by a good friend of mine and he says it feels good now? Hopefully it isn't temporary??? I will fill you guys in later on.

 

[JRODS*LB7]

:woott: