1999 Vortec 7400 injector swap

[montess85]

i upgraded the injectors on my 1999 GMC 7.4 from the factory one to the ls1 injectors. Truck runs good now. but I now have a SES light on. I have a p0172-p0175. Both rich codes. I assume its because I have bigged injectors. I was under the impression from all that I read here that it was a direct swap. Do I need to have a tune to run these without getting a check engine light. Also my mileage went from 12-15 down to 8-11.

 

[brycebba]

I know a few have done this swap on here without having to program but I had a hell of a nightmare time with the 3 sets of LS1 injectors I tried. They flow too much fuel for stock programming. They are at least 24lb if they are factory and ours run 19lb stock I believe. You are getting worse mileage because the injectors are putting in too much fuel without programming or supporting mods to balance that like a cam or other internals.

Me and 88GMCtruck both had a terrible experience in various ways and ended up paying more to get good injectors from fiveo motorsports. I got the 19lb blue Knights and then used a 350 fuel pressure regulator so I run at 4 bar instead of 3 bar.

I hate to throw out the blanket statement but I honestly think that the LS1 injector swap is a bad idea and more often than not the injectors are not going to work properly. I had to change mine so many times that I can do the job from start to finish including the removal of the grill in less than an hour.

If you keep em I hope you have a much better experience than some of us have.

 

[dr_goodwrench66]

I read the same thing about the LS1 injectors. I ended up going with the Lucas injectors from Five 0. I bought these style simply to try and squeeze mileage out of mine.

I do believe that with some simple tuning with EFI Live or equivalent, your problem can be corrected.

 

[montess85]

i was going to get a tune from Black Bear Performance. I will tell him my problem. Hopfully he can get it to work. I really dont feel like changing them again lol

 

[brycebba]

I hear ya! It's not the most fun thing. I would strongly suggest you eat the 50 dollar core and just keep your pcm. I have already sent mine back for a retune and just threw my old one in to get by.

Oh and people say that you have to do a crank relearn or something like that if you use a different pcm since the VIN doesn't match but my 96 didn't. I threw in the pcm that was not originally mine and it worked fine.

 

[DRAGGIN95]

I also used the Lucas injectors from 5.0 in my 2000 454 dually, worked great, I also changed the EGR and FPR while I was at it.

 

[Spastik Monkey]

So the ls1 injectors are a straight swap? Plug and play?