LS motor problems

[payne97]

I have a 04 lq4 when n park rev good like 5500 put it n drive wont rev no more that 2000 it has been changed to cable throttle body
any help would be great thanks

 

[95limitedzj]

have a diagnostic code reader? Any codes? Who did the wiring/ pcm tune? don't have much information to go on. TH400 as in signature?

 

[Burttyler]

Probably need the computer remapped for drive by cable

 

[payne97]

I did the harness
computer is out of a 2000 model truck and all of the bullshit has been deleted it is showing no codes
was looking more towards the fuel filter or fuel pump(MSD) would it make it do that

 

[Burttyler]

dont think it would be a fuel issue because it revs in park. i could be wrong but i think youll need the computer remapped or another computer for the cable drive. when you put it in drive its throwing it into limp mode

 

[payne97]

Ive got a older computer out a 2000 truck that had a cable on it
Change filter same ****
And yes its got a 400 behind it its my tow rig

 

[Burttyler]

Hmmmm I don't know with out looking at it and hearing it. Hope u can get it figured out

 

[payne97]

Yea im n the same boat it at a friend's house n TN he's try 2 get it running 4 me

 

[alli85]

I'm not a professional or anything just going off first hand experience. Mine was acting real similar to what you said in park it sounded fine when I would rev it up but put it in gear and it wouldn't rev & start popping like crazy seem like a fuel deal & long story short after hauling it to Lane Culver he walked out walked up to it still on trailer and the back plug wire was bad but if you just pushed on it or looking at it you couldn't tell it was bad. Never even started it, mad me look like a fool but I had checked them several times just never pulled on them hard. It's worth checking.

 

[snoball]

Just because it will rev in park doesn't mean it's getting enough fuel to run good under load. Had a similar issue and fuel pressure gauge showed it losing pressure only under load.

Use a laser thermometer and chech each header tube to make sure all are firing but I don't think that would make it not rev.

 

[payne97]

Going 2 order a new pump
ive read where the MSD pump is junk

 

[kenwor]

Check fuel pressure. If a cylinder isnt firing it will still rev. Should be more like popping if its misfire. It doesnt sound like computer issue but it could be if it was damaged.

 

[payne97]

Its on my old chevy I believe its the fuel tank selector valve