LS3 fuel/throttle cutting early?

[Kalvin.I95Muscle]

Getting my tune ironed out and feel like it's doing really well, I've ironed out pretty much any of my knock retard I think.

The issue I'm having is when I do a decently hard pull it does completely fine through the first and second gear but once I get into third it seems to do a fuel cut. like I hit rev limit or something but it does it at like 5k rpm. I can go higher in the rpm range if I'm not WOT.

I have dialed my MAF in some, and done a round or two of SD tuning to get it closer.

Stock LS3 TR6060 swapped into a 74 Blazer. E38 ECM. You can see it cut fuel near the end of the log, I stopped the log a few seconds after the pull.

Any help is greatly appreciated.

Latest MAF TUNEED.hpt

25-07-12 09-44-32.hpl

[DanN]

Do you often lose your speed signal? At 2 minutes 20 your speed signal leaves the chat..

[Kalvin.I95Muscle]

Actually it's funny you say that. I did replace my speed sensor recently thinking that was the issue, and it typically only does it when I'm WOT. Wonder if I have a bad connection on the VSS connector.

[DanN]

Full disclosure: I am a complete noob when it comes to tuning, but as a diagnostic tech I like to make sure all the basics are working properly before I spend a bunch of time on diagnosing a problem.

[Kalvin.I95Muscle]

You're a smarter man than I am lol. My mind doesn't comprehend why this little thing could be linked to that thing, however I can wrench and build stuff just fine. It's the fine tuning that I suck at.

I bet Voltage drop is going to be one of my issues here, I just need to figure out where and why.

What's up with your spitfire? I own a classic car dealership and recently sold a 73 spitfire, and still have a 65 with a buick 300 alum heads, th350. pretty cool car

[DanN]

You're a smarter man than I am lol. My mind doesn't comprehend why this little thing could be linked to that thing, however I can wrench and build stuff just fine. It's the fine tuning that I suck at.

I bet Voltage drop is going to be one of my issues here, I just need to figure out where and why.

What's up with your spitfire? I own a classic car dealership and recently sold a 73 spitfire, and still have a 65 with a buick 300 alum heads, th350. pretty cool car

I don't *know* that the speed signal is the issue, but it seems awfully coincidental that it correlates with your power dip. Maybe it's not the problem itself, but a symptom of something else; bad connection somewhere, perhaps a grounding issue, PCM pin pushed out, etc.

At 2:42 in the log, did you lift off the pedal, or did we lose the pedal signal, too?

The Spit is probably the best indicator that there is something wrong with me. HAHA.

Supercharged 2L (LSJ) from a 2007 Cobalt SS, Tremec T5, Subaru 3.54:1 VLSD rear end, GT6 rear "Rotoflex" suspension converted to CV axles, GT6 brakes all around, obp pedal box, electric power steering. Paint is HoK Kandy Tangerine. I bought it as a box of parts in 2007, on the road for 4 years now.
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[Kalvin.I95Muscle]

I believe you're right. Further down on the list you can see control module voltage and it lingers between 12.5v or so and 13.4 volts. When I went WOT it stayed below 13 and right at the cutoff point (ecm cut off fuel and throttle as I was still in it when it stopped) it actually dipped to 11.9 at the very instant it cut.

Looking back at my log from the startup this morning the only time it ever reads 14+ volts is when I first start it. I do have some loads to include electric power steering, electric fans, and AC but that's about it for heavy loads. ECM and the normal stuff is really the only other loads.

I'll keep looking for voltage drop solutions to make sure I'm not losing voltage where I shouldn't be.

That is probably the nicest Triumph I've ever seen btw. Love it! I wish I saw more ecotec swaps. I'm also kind of interested in this 4 cyl LS I saw released a couple years ago. not sure what will come of that.

Here's a pic of my blazer and the Spitfire we have lol

https://photos.app.goo.gl/LidqQjE8iz7qMV1FA

[DanN]

That looks like a garage I'd very much like to hang out in. That Blazer is sick. You'll probably appreciate this little truck I've been helping build. https://www.instagram.com/p/DLqr5-EPGw7/

What's the asking price on the Spitfire? Just curious - I already have 2 1/2 of them.

I was having voltage problems on my Canyon. Some dummy (me) forgot to tighten the battery terminal on the alternator. Something simple like that can really mess with your day.

[Kalvin.I95Muscle]

That truck is sick! Yes I very much like!

https://i95muscle.com/1965-triumph-s...-28348/7274017

it's a fun little car, but you know more about that than I would.

Do you or anyone else stumbling upon this know if there is any shortcomings to using the 4 pin to 2 pin adapters for the 2 pin alternator that came on the 2013 Camaro? The harness I have came with a 4 pin connector so I run the adapter. I will absolutely go get a different alternator if I need to but also would be happy not spending $200 for something I already have if it doesn't make much of a difference.

I'll double check all my power wires to make sure they're tight. Thanks again for your input.

[DanN]

I don't know much about the 4 to 2 pin adapters myself, but I am aware they can be problematic in at least some installations. GM has different methods for controlling the alternator (voltage and PWM) and the 2 don't mix well. I would get the alt that matches your ECU. I had that exact problem with my LSJ and had to swap alternators.

Whoever built that Spitfire should have just gone full Gasser with it. It looks about 1/4 gasser now. lol.