New High Boost/Load Sputter - COP Kit (w/ Logs)
 

All,
After taking the car out of winter storage, it acquired a sputter/hesitation under high boost. After first, it only happened momentarily at around 30psi, but it's gotten progressively worse. Now it won't even hit 25psi without falling on its face.

Things I've done in an attempt to fix it:

• New fuel
• New spark plugs (BKR7E at .28 gap)
• New Coils (car has a Trackspeed Engineering Coil on Plug Kit)
• Re-calibrated LC2 Wideband O2.

Again, these items and tune were all working well to put down 400whp at the end of last season. I was also considering it was a fuel starvation problem, but duty cycle seems well within reason. Could it be a Ground issue? Or perhaps something else in the ignition system? (the harness?)

Log attached. Any thoughts would be appreciated.

Thanks!

Have you checked/logged fuel pressure?

Only AFR and Injector Duty Cycle. Is this not conclusive enough?
I will also revisit my fuel lines and the vacuum line running to my AFPR today.

You are spiking lean right at the end. No bueno. Can you post your tune? A weird thing I noticed is your coolant temp spiked up 10deg right exactly where you start losing power. Seems an odd coincidence. Do you have some kind of CLT safety in place?

Reason I ask is that new plugs didn't help, and the sputtering is slowly lowering where it starts. Sounds like it is progressivly running out of, something, up top. Might be in the fuel system starting to go.

My friend's car does this when the plug start to fowl, but you changed those already.

Also - can you provide a brief description of your setup?

Injector Duty Cycle does not log fuel delivered. Just tells you what your injectors are doing. With knowing the fuel pressure you are kind of blind.

Also, do you not log intake/manifold air temp? How in the world do you adjust for 50deg swings of air temp during a run up? To 30psi?

Also, I would go ahead and find a boroscope to look at the tops of your pistons for signs of detonation.

[you are brave my friend]

Crankshaft Position sensor. Check the gap itll produce issues when they start going out.

The lean spike is the misfiring. Uncombusted oxygen in the exhaust will register as lean.

Can't really be the CKP sensor IMO. He has no sync loss.


The biggest issue I can see from your log is your battery voltage. The megasquirt is showing 17+ volts. Grab a multimeter and confirm.

• Tune is attached
• I do not have CLT safety in place at this temp range
• I do not think it's fuel related. I attached another log of it happening and you can see AFRs are not going above 12.0. I think whatever is causing the issue is causing the car to lean out bit.

• Built engine w/ GT35R (build thread here, and I think the content is still current).

• Regarding injector duty cycle: my thought was DC would increase to compensate for lower fuel pressure (for example, if your fuel pump is too small, you could max out injector DC even thought the injectors could flow more. I imagined that a reduced fuel flow would act like a under powered fuel pump). But was a total guess on my part.
• I don't log intake/manifold air temps (though if you have any references on how to, I'll certainly read up). That said, I use mechanical knock sensors to ensure the car isn't detonating.

Gap looks dead on. I ordered new crankshaft and cam position sensors thinking one of them could be the issue. They should arrive by Thursday.

Long story short, voltage logs have shown 17v for years.:facepalm: so I suspect it's something else.

Because it's progressively getting worse, and load based, I can't help but think it's a connection, a sensor or a ground etc. 🤬.

Actually, I just did some reading and I have a hunch that it's the capacitor within the ignition harness. I think it would also explain why I'm still able to go beyond 20psi, but not 30. I'm going to open up the harness tomorrow and see of Amazon offers a replacement capacitor.

I would check ground connections for the ignition coils. I don't drive my car very often, but I had something similar this time around when I took the car out of the garage.

I have ls2 truck coils and could push the boost up, but was getting random misfires above 17 psi. I went through everything on the wiring including cleaning the ground for the ignition coils, changing spark plugs, reseated all of my spark plug wires and made sure all connections were clean. No more misfires

Edit: I wouldn't worry about the capacitor until checking everything else first

Reflash the firmware. I've run into the same issue, don't know what causes it.

Here's what I've tried at this point and it's still doing it:

• New fuel
• New spark plugs (BKR7E at .28 gap)
• New Coils (car has a Trackspeed Engineering Coil on Plug Kit)
• Re-calibrated LC2 Wideband O2
• New 10,000uf Capacitor (for Cop harness)
• New Crank position censor
• Scrubbed the grounds (behind exhaust manifold, and on throttle body)
• Turned off all boost cut features (fuel/ignition in Tuner studio)

I'm going to try re-flashing the firmware (if anyone's got a good how-to, please share; it's been years since I did it last).

Outside of the firmware, what the hell else could this be? Ugh, so frustrating since the car's been running well for a while. :facepalm: Thanks for everyone's thoughts thus far.

Car died entirely. What I know:

• While driving, it stalled
• All the lights/dash are still lit
• Car still cranks but does not attempt to start
• Fuel pump does NOT cycle when key is turned to on position
• My laptop no longer acknowledges my DIYPNP megasquirt

Because of the fuel pump and the laptop not acknowledging the MS, I'm guessing the MS isn't putting out a signal. So I guess the question is why? I'm going to pull it off the car tomorrow and see what I see.

Sounds like grounds/wiring, check fuses. Good luck, that blows!

Check your big INJ fuse in the engine bay

This happened to me. Turns out my cam sensor wiring grounded out on my hood after it rubbed a hole through the insulation (VVT cam sensor position) . I had tied it into the injector power white/red.

Start looking for witness marks on parts or braided lines that might have worn through and cause undesired shorts.

EDIT: (This was an unrelated issue) It's now popping the 30amp fuel injector fuse after running for a few seconds...... Clues.

Look for shorts. Trace everything you've touched or rewired. It doesn't have to be big, it could be rubbing against your intake manifold.

Insulation wearing explains the slow progression to failure.

Thanks for the tips! There was a short. The car is now back up and running. Only issue is the original problem of the car cutting out is still happening.

I'm back to investigating fuel instead of spark. I'm replacing the fuel filter next. :vash: