well guys trying to get the lq4 runnin in the 69 c10. I had a complete 99 5.3 and got a 04 lq4. put all the 99 stuff on it and had a mail order tune done. told the guy it was a 04 but forgot to tell him it was return style system. so im thinking he put a ruturnless tune in it. It wont start unless you hold the throttle open a bit and it surges real bad and wont idle. Wondering if anyone has had this problem or has any other ideas what it mite be. Im going to go plug the return and see if it runs. any help would be great.

 

Doesnt matter if it is a return style or not. Either way the pump creates the pressure to the rail. The only difference is the excess bleeds back to the tank. I dont think you would need to specify that in a tune.

 

well i just plugged the return and it does the same thing. it fires at first and dies. it will only run if you give it throttle and it will rev way up and die out then rev way up and die out. dont know what would cause this surging. any adeas?

 

The injector flow rate table is COMPLETELY different between the 2, although, it should start. Returnless system has the IFR table on a curve, to compensate for different vacum levels in the engine. Return systems should have a flat number all the way across.

 

well i changed out the throttle body to test a differant tps and it runs a bit better but still wont idle and surges and now seems to cut out above about 3000-3500 rpm. man i wish i had efi live so i could check the tune and scan it.

 

What??


Yes it does matter BIG time! As wkdivr stated with a vaccum referenced regulator your IFR table is linear across the board if you have say 31 lb injectors then that's what is set across the board but without a vaccum referenced reg. then the IFR table is scaled COMPLETELY different and would make quite a difference in the way that truck is going to run.

 

Also who ever tuned it needs to make sure that they have all the info on those injectors because alot more goes into tuning injectors than just rescaling the IFR table. The Offsets, min. inj. pulsewidth, etc... all needs to be changed.

 

the tuner was aware of the size and type of injectors as well as the cam. im trying to rule out if its a sensor or if the pcm/tune is bad. guess it could be a bad ground or wire too. heres a vid:
http://s280.photobucket.com/albums/k...t=DSCN0383.flv
anyone ever encountered this?

 

well i went to the car craft summer nationals in minneapolis this weekend ( had a great time) and talked to a few vendors. one told me to reset my iac. did that and it idles good now. getting my cooling system hooked up tomorrow so i can run it for more than a few seconds. then i will see how it runs above idle.