Need Help 0411 swap 98 GMC 7.4

[NateSvob]

Hello all, I am needing some help figuring out my issue. My truck is a 1998 GMC 3500 4x4 7.4 9200lb gvw. I rebuilt the engine and installed a comp cam XR264HR14, shorty headers and 36lb injectors. Also did the 0411 swap and had it tuned by blackbear. After everything has been installed, I can get the truck running but not well. After some months of diagnosing, fixing and swapping parts I still cannot get it figured out. The problem is that it is basically dead on 4 cylinders, or it is over fueling on 4. Runs very rough and pops through the exhaust often. When checking the headers with a thermo cylinders 4,3,7, and 2 are cold and the others are like 150 degrees warmer. I have checked spark on all cylinders and compression (only on cylinders 1 and 2 at this point) changed distributors twice worked on Crank sensor signal checked pinout several times, checked and repaired grounds, done the relearn, probably countless other things I'm forgetting. One question I do have would exhaust cause this as I only have enough of my old exhaust on the headers to allow the front O2 sensor to be present. I am going to try and post my tune here and a few log files of it running. If anyone can see something I'm not or knows what it could be that would be great. Also let me know if there is something I'm forgetting to tell you guys and gals. Thanks!

mytruck.hptanother quick run.hplrun 2 4500.hplred truck second run.hpl

[gtstorey]

You need at least 18” of pipe after the o2 sensors. Preferably more.

[Scott-m]

Wow I have the same L29 with comp xr-264hr-10 and 0411, and even have been using black bear. Assuming no mechanical problems like a wiped out cam (check your oil for metal), it has to be either fuel or spark. I had the whole left bank not running at first, and it turned out to be the injector harness plug. I pulled the top half of the manifold and found no continuity between the individual injector connectors and the pink +12v common wire. I cleaned the main harness connector pins with a small wire brush and put on some anti-corrosion electrical grease, and that worked. Double check the continuity before putting the manifold back on of course..

I have been posting on here lately about black bear, and what I thought was a lack of ignition timing in the tune. I sent mine up several times until they shut me up by putting way too much timing in it. It should be back early next week with the perfect tune..

https://forum.hptuners.com/showthrea...-Timing-at-WOT

[SiriusC1024]

I have been posting on here lately about black bear, and what I thought was a lack of ignition timing in the tune. I sent mine up several times until they shut me up by putting way too much timing in it. It should be back early next week with the perfect tune..

https://forum.hptuners.com/showthrea...-Timing-at-WOT

Prepare for disappointment. Got that MPVI on order yet?

[horsepowerguru427]

Prepare for disappointment. Got that MPVI on order yet?

XD people dont realize that mail order tunes are just cookie cutter tunes like plug and play handheld tuners.... no data to give them for accurate changes, then its just guesses.

[NateSvob]

I realize that could be a problem that?s kinda why I bought the MP3 so I can tweak some things? problem is I just don?t know enough about it as to what to change? Any help would be great

[NateSvob]

I can check injectors again but last time I had the plenum off I had some crank it over and I verified all injectors were spraying. It?s as if it?s fueling or firing at the wrong time. I messed around on the VCM Scanner yesterday for quite awhile adjusting spark and things? at times you could hear it smooth out but it still never hit on all eight!

[NateSvob]

I do think I?m going to talk to exhaust shop and see if they will install the exhaust without it running and see if that helps anything

[Scott-m]

Check compression, plug wire firing order and the injector wiring sequence at the ecm.

I was joking, of course it won't be perfect..