LB7 Wont Drive

[MMLMM]

Ok came across this today.

LB7. Truck starts and runs fine. On a stock tune it will drive but drive crappy. Put a good size tune in and it runs good. After awhile start it again and it runs but wont really drive. It can idle around just fine but seems like there is no throttle there.

Flash stock tune in again, truck drives now but wont run very good, seems like it stops fueling around 50mph.

Flash Big tune in again, Truck hauls ass and runs great. Everything seems fine. Then Shut it off for a few hours and start it again and back to square 1.

 

[stacks04]

possible the main connectors are acting up?

 

[FMOS]

Fuel line issues between the tank and CP3???

 

[duratothemax]

this is an electrical issue.

bad ECM is my guess.

 

[McRat]

Lift pump is starting to fail?

 

[MMLMM]

this is an electrical issue.

bad ECM is my guess.

lol, anything but an electrical issue please!

Yea its funny. It comes and goes. It seems to be fine after a flash. You can shut off the truck and restart and still god. Its like after it sits and cools down it comes back.


Idont think its a mechanical fuel issue as once a big tune is reflashed in it rips around pretty good like it should.

 

[SmokeShow]

Am I understanding correctly that it never runs good (aka runs good while driving around) on a stock tune though? only time it drives around and runs good is with the big tune for a limited time period?

Safe to assume there aren't any logs for smart ones on here to look over?


C-ya

 

[MMLMM]

Am I understanding correctly that it never runs good (aka runs good while driving around) on a stock tune though? only time it drives around and runs good is with the big tune for a limited time period?

Safe to assume there aren't any logs for smart ones on here to look over?


C-ya

On the stock tune it seems to be weird. Haven't flashed the stock tune in after the condition on the big tune to see if it goes away. Going to try that.

Once you flash the big tune in the truck runs awesome for awhile, than after it sits, you start it and its like theres no throttle. It recognizes throttle, but doesnt really do anything. So you flash a new tune in and it seems to fix it for time being.

The MAP sensor got broke before this condition. A new one was put it and it didnt change. Then the broken one was fixed (it was its mount) and re installed and now the truck only does what I am explaining. So not 100% sure its MAP related. there was a Baro code and underboost code with the stock tune.

Also will have some logs this afternoon.

 

[duratothemax]

this is NOT a fuel delivery/mechanical/physical problem, I 100% guarantee it.

wiring, or ECM

 

[McRat]

Yeah, logging it will show where the fault lies:

Pedal position
RPM
mm3 of fuel
Commanded and Actual rail pressure

You need a "good" and "bad" sample.

 

[GMC_2002_Dmax]

Ok came across this today.

LB7. Truck starts and runs fine. On a stock tune it will drive but drive crappy. Put a good size tune in and it runs good. After awhile start it again and it runs but wont really drive. It can idle around just fine but seems like there is no throttle there.

Flash stock tune in again, truck drives now but wont run very good, seems like it stops fueling around 50mph.

Flash Big tune in again, Truck hauls ass and runs great. Everything seems fine. Then Shut it off for a few hours and start it again and back to square 1.

If it is a 2001 flash it to a 2002 OS/15186006

If it is a 2002-2004 send me the stock tune file, I can provide you with a "good" stock tune to try in its place.

I would suspect a corrupted OS/Tune file.

 

[MMLMM]

If it is a 2001 flash it to a 2002 OS/15186006

If it is a 2002-2004 send me the stock tune file, I can provide you with a "good" stock tune to try in its place.

I would suspect a corrupted OS/Tune file.

its an 04. I have updated it to a 9044 os. I have a fresh stock os and it still acts up.

when we start it, give it throttle it climbs to 1800rpm normally, then real slow to 2000rpm then it will rev past that normally

 

[MMLMM]

when you floor it up to 2k its like there isnt any fuel.

after 2k it comes alive and plenty of fuel and runs good.

Truck ran fine with this tune before.

acts up with any tune put in it all of a sudden.

all connectors and wires are plugged in and look fine.

gonna try another ECM later or tomorrow.

 

[GMC_2002_Dmax]

Does it have a high idle switch........

 

[MMLMM]

yes, and seems to work like normal

Dsp5 also but no dsp os in there right now.

both are hooked up correctly.

 

[duratothemax]

Does it have a high idle switch........

tony if it did have a high idle switch and if it was left on accidentally it would never go above 2000/2200 rpm at all. He says its slow to 2000rpm but does rev above that.

its something else electrical. See if you can swap another LB7 ECM in.

 

[GMC_2002_Dmax]

tony if it did have a high idle switch and if it was left on accidentally it would never go above 2000/2200 rpm at all. He says its slow to 2000rpm but does rev above that.

its something else electrical. See if you can swap another LB7 ECM in.

My high idle is active in Park, not in Drive.

Also if I place my foot on the brake it will kill the high idle and allow it to rev past 2000 rpms.

I was asking because anything extra on the truck or added could cause funny things to happen.

I would also check the ECT sensor, there is a cold engine fuel limiting table as well.

 

[MMLMM]

My high idle is active in Park, not in Drive.

Also if I place my foot on the brake it will kill the high idle and allow it to rev past 2000 rpms.

I was asking because anything extra on the truck or added could cause funny things to happen.

I would also check the ECT sensor, there is a cold engine fuel limiting table as well.

I gotcha on the high idle, I will have him disable it so its not a worry. Good thinking right there. after awhile of thinking about so many things sometimes it can be the littlest things to bite you in the butt lol. Hopefully its that simple.

as for the ECT, At first I thought it could be due to the temp tables, but I went through and couldnt find any that would limit us. Then realized after the truck is warm it still does it. The log show its between 181-195 during the logs....
I have B0729 set to 120, so theres no limiting there.

 

[bullfrogjohnson]

what about the baro sensor? This will cause all the problems you are talking about.

 

[duratothemax]

wait so even with the stock tune it acts weird? Im really confused...