dreambird

Been having a issue lately with my LQ4 swapped 3rd gen. I am using the DBW from the 2003 2500HD it cam out of, it has headers intake and speed density tune by PCM for less, aside form that its stock. When I first drive it it performs fine no issues the longer I drive it the worse it gets. It is fine at idle to half throttle once past that point the engine dies, the MAP sensor on my scan tool reads atmospheric 29.92ish as I lift of the throttle the engine comes back to life. I am not getting any check engine lights or stored codes. If I shut it down and restart it it will initially run fine but come back shortly after. I checked the throttle body with the engine off it actualites just fine not hesitation. There is no misfire it just dies, as I let off the throttle it will buck and miss some until I get to the throttle point it is happy at. Could it be the CAM or Crank position sensors? Any thoughts? Thanks for any help and insight

G Atsma

Clogged fuel filter

dreambird

Its a pretty new filter. I just had the tank open and it was pretty clean as well, I checked for bad hoses in the tank and they looked good. The fuel trims are about perfect as well, especially since I also just also replaced all the injectors. It is a instant drop off not gradual.

G Atsma

OK, cool. Check ALL connections including all grounds. You might have a connection that as it warms, expands apart and loses connection until even a minute later it cools enough to regain connection.

dreambird

Ok I checked all the grounds which are bolted to the LH rear cylinder head and they where all secure. Pushed on all the sensor connections, got a slight click from the CAM sensor going for a test drive to see if that affected anything.

G Atsma

There are other grounds besides the ones you mention. Check them ALL

dreambird

I hear you there. When I wired the harness years ago I directed all the grounds to that point. I also checked the battery and and the block to chassis they are good. I have some scanner info; timing idle 18d, driving 31.75d, during issue 24d. Throttle position indicates 99.7% during issue or where ever I have the pedal. MAP shows 8 to 12 in hg driving, 29 during issue. Alt 14.1v. Short term fuel trim driving 0 to 3 goes to 0 during issue. Long term fuel trim driving 1 to 4 about 5 to 8 during issue. It does actually pop some during the issue as well. I am thinking about just replacing the CAM and Crank sensors since they are original and I don't know when or if they have ever been changed.

dreambird

So I replaced both CAM and Crank sensors no change the issue begins at 60% throttle if I back off to 50 it comes fully alive. If I hold my foot down it will spit and sputter and is worse right at 60 65% throttle. Starting to wonder if the ECU is messed up? On Friday the alternator started acting haywire voltage up and down was able to drive it home replaced it and voltage was perfect 14.1. Is there a way to test a computer? Thanks again for any help

G Atsma

If the voltage was going nuts I too would wonder if that could have fried part of the ECU.

dreambird

I am glad you agree with that. I may send it to PCM for Less where I get it tuned and see what they think, and if its jacked up just put my tune into another ECU. It should run amazing once it's fixed up to 60% it's running the best it ever has since I put the new injectors in. Thanks for your help

dreambird

Ended up being the Aeromotive fuel pump, I figured out how to see my fuel pressure gauge while driving and eventually noticed it dropping under power to 20psi and back to 58 in cruise. Thanks for all the help! It now has a Delphi from Napa