Hello ive been chasing this issue for a while and I can’t seem to figure out what’s wrong. Car drove perfectly fine until one night it started to sputter over half throttle. I have a turbo 1.6 with megasquirt, dw200 Fuel pump, K tuned AFPR, 850cc injectors, bmw VTPS. Running e85. Fuel pressure is set at 50psi, car idles and cruises fine but when I give it 50% throttle or more it sputters at 4200rpm. I can reach 6000rpm just fine as long as I’m not over half throttle. When it sputters it goes rich and timing drops lower. Could the tps be going out? It reads 0%-100% fine but when I go to calibrate tps the blue bar shows When I’m not on the throttle(pic attached)

 

Check your grounds. I had the EXACT same symptoms on my '97. It ended up being a loose battery terminal. Seems like your spark plugs aren't generating spark when the cylinders are consuming more air and fuel.

I'm not familiar with TPS sensor calibration so ignore if you're certain that's the problem.

 

I came to the conclusion that I have a spark problem. I’m running the flow force LS coils so I’m wondering if one went out. So I put my stock coil pack back in and now it’s a lot more aggressive, instead of sputtering like it’s hitting limiter it’s now backfiring like it’s boost cutting at 50% throttle.

 

Sounds like it’s time to pull out your spark plugs and inspect. They can tell you a lot just by looking at them. Properly gapped as well?

 

My Last set of spark plugs were gapped by my tuner which held perfectly at 17psi for a few weeks until it started sputtering. I changed them and gapped them with my cheap gap tool I believe to .030. I should re gap them with a feeler gauge. Here’s a pic of my spark plugs right now, left to right #2 looks like it’s blowing out.

 

Did you change your dwell and spark duration settings according to the flow force instructions?

 

yes since I have MS2 I set nominal dwell to 3.0 I was tuned on the ls plugs which did great until now. I just replaced the ls wires from flow force back to my stock ones but still using the ls coils and it’s a lot better but still does the same thing just not as much.

 

.030" and 17psi is a huge gap. Put them down to .020-.025. I agree, it sounds like a spark issue.

 

I just gapped them down to .022 and it’s a little better but still does the same thing. Drives good under 10psi but anything over that it will sputter

 

It was a bad ignition coil, took me a while to find out considering I probably bought another bad one from the junk yard but I eventually found the bad coil and swapped it with a good one. No issues.