Finished up my build a few weeks back and been great since. Got it dyno tuned here locally in PHX. But lately it’s been cutting spark real bad and not sure why. This is my first turbo build and 18 years old! Quick rundown on the build:
vs racing billet 7875
4.8 with cam and springs only
deka 80’s
th350 3000 stall
br7 plugs gapped to .25
heat wrapped everything
e fans
vs racing bov and gate 12 lb spring on MBC to 15 psi
bosch 044 GOOD FUEL PRESSURE

need any help I can get!! Will let it spool to 3k floor it and it lean pops and cuts out real bad wideband goes all over the place need help!

 

Have you checked under the heat wrap for any cracks in the hotside? Check the connections to the injectors, I had one wiggling once that would hit the wires going to the O2 sensors and cut out under load but came back once it was low RPM because the engine would push just far enough over under the load twisting to make contact.

Do you have anyway to run a scan and log PCM data?

If an injector on a cylinder stops working it makes the wide band go super lean even though the other cylinders might still be firing at the proper AFR because of the added fresh air to the exhaust. Also it makes it sound like **** and not pull RPM. If it stops at 3k that sounds like more than one cylinder out.

Considering it worked good and then didn't I would be leaning ore towards injector/electrical/regulator problems than fuel supply. Does it happen to be doing this the moment boost starts to build? Could hope for it to be a vac reference problem and as simple as putting a blown off line back on...

 

no cracks and all connections are good. I have HP tuners I can try log and upload a log... it seems to only happen 1-2 seconds after I’m in WOT in full boost... it will pull super hard but then dive lean to around 13-14 and then studder and pop real bad and I just let out at that point... also tachometer shift light will illuminate and needle will act up. Not sure if that has anything to do with it or if that just has a loose wire. Just thought I’d throw it in there. Really stuck on this one!

 

Ya run a log. The tach needle thing is strange. My first thought to that is you have a bad ground. make sure your engine to body ground is good, engine to frame ground, etc...make sure the coils are grounded and all the connections are secure. It sounds like its leaning out from misfires. The magnetic coil packs from early LS engines are known to crap out and get weak. I'm fixing to replace mine soon. Most people will lose RPM and power up at 6k though from that not 3k.

You have an electrical issue. Not that I think it's likely but run the log and make sure the scanner is reading RPMs properly and that the RPM it's scanning aren't also jumping around like the dash tach.

But ya, electronics jumping around plus misfires....red flags for ground issues and checking connections.

Can you make it do it in the driveway in park as well? If so can you get noid lights on the injectors?

 

Any DTCs in PCM? Wouldn't hurt to tighten plug gap to .020" especially if you plan to max out the turbo.

 

Tightened up the gap to about .21. No change. Tomorrow once it’s all cooled off I will check all the grounds and clean them up and try it again. Just weird because it started doing it out of no where. Hopefully I can narrow it down! Just wanna do some clean safe pulls lol. My brother has my HP tuners software right now so a log might be a few days. I’ll keep you posted tomorrow.

 

no DTC’s. Tightened up the gap, no change. Any other ideas?

 

Do you have a scan tool that can show you mode 6 data? Possible crank sensor? Scope output or swap. Wiggle test harness to see if you can induce problem.