Not fuel cut.. What could it be? [video]

[91CoupeMike]

So my foxbody is having the same issue as before and I had thought it was cutting fuel.

When racing, above 6k randomly will cut off. It's not consistent at all. It happened 4 times Tuesday when I was out messing around and once tonight at the track. On my 2-3 shift I went to shift ~6400ish and it fell on its face and AFR was in the 10s-low 11s at wot.. 8.6 at 60mph coasting. What a turd! A quick key cycle and it was fine.

So curious on my way home I just took 4th to 6500 and I kept my foot in it and nothing happened.. Held it there for what seemed like a few seconds.. Still wasn't satisfied so I pressed the clutch and eased the rpm up to 6500+ it seems like it's floating valves and not wanting to rev but doesn't cut fuel or shut off.

Short of a bad 20 year old computer and/or faulty chip, what could it be?

Should I just datalog until it happens? Would that show me what's going on?

I don't want to add the nitrous until I am sure It won't shut off randomly while on the pill.

[One zero]

Any read on fuel pressure?

[91CoupeMike]

Any read on fuel pressure?

No all I have is my stock gauge cluster and a wideband

[Slow Five-O]

My guess was going to be valve float.
6500 is on up there for stock motor.

[91CoupeMike]

My guess was going to be valve float.
6500 is on up there for stock motor.

Yeah I can see that being why it won't rev out past 6500, and that's fine with me.. No need for that.

But what's up with the falling on its face when I shift 6k + randomly ?

And the rich condition afterwards.

[danielhv]

I still think you should swap the ECM to eliminate that as a suspect.

If that doesn't fix, I'd be looking at fuel pressure, vent lines, etc.

Sent from my SAMSUNG-SGH-I747 using Tapatalk 4

[Lone Star Performance]

Spark blow out maybe?

[jw33]

If the A/F is not going lean it sure sound like an ignition issue. I've had terrible luck with aftermarket ignition stuff and had to add shielding to wires that has cleared up things in the past. Are you just data logging A/F with a wideband O2 or do you have something on the ECU to catch everything?

[Dacotua]

So my foxbody is having the same issue as before and I had thought it was cutting fuel.

When racing, above 6k randomly will cut off. It's not consistent at all. It happened 4 times Tuesday when I was out messing around and once tonight at the track. On my 2-3 shift I went to shift ~6400ish and it fell on its face and AFR was in the 10s-low 11s at wot.. 8.6 at 60mph coasting. What a turd! A quick key cycle and it was fine.

So curious on my way home I just took 4th to 6500 and I kept my foot in it and nothing happened.. Held it there for what seemed like a few seconds.. Still wasn't satisfied so I pressed the clutch and eased the rpm up to 6500+ it seems like it's floating valves and not wanting to rev but doesn't cut fuel or shut off.

Short of a bad 20 year old computer and/or faulty chip, what could it be?

Should I just datalog until it happens? Would that show me what's going on?

I don't want to add the nitrous until I am sure It won't shut off randomly while on the pill.

Your getting fuel cut whether you want to accept it or not. The stock Ecu will cut your fuel at APPROXIMATELY 6250. It depends on conditions. It could be more on the right conditions. The computer calculates your fuel cut by the PIP number. You need to raise the Max PIP on your computer. Buy a Tweecer to do it yourself.

When it gets NO FUEL, your RPMS immediately drop, computer senses it dumps fuel and it will show rich before stabilizing

[91CoupeMike]

If the A/F is not going lean it sure sound like an ignition issue. I've had terrible luck with aftermarket ignition stuff and had to add shielding to wires that has cleared up things in the past. Are you just data logging A/F with a wideband O2 or do you have something on the ECU to catch everything?

Just a w/b that I glance at every now and then. Not logging anything currently.

Preparing to just drop coin on a QH.

I have stock dist and tfi with msd coil and Taylor wires, routed and loomed neat with none touching.

[91CoupeMike]

Your getting fuel cut whether you want to accept it or not. The stock Ecu will cut your fuel at APPROXIMATELY 6250. It depends on conditions. It could be more on the right conditions. The computer calculates your fuel cut by the PIP number. You need to raise the Max PIP on your computer. Buy a Tweecer to do it yourself

Car has a custom chip with a tune. It was floating valves in nuetral and not shutting the fuel off at 6500-6700 last night.

[Dacotua]

Car has a custom chip with a tune. It was floating valves in nuetral and not shutting the fuel off at 6500-6700 last night.

It depends on condition dude. Your PIP is calculated by several of your sensors. When your PIP = Max PIP you will get fuel cut whether its at 6250 or 7000 RPM.

You are getting fuel cut

[Grape]

I feel bad for any shop whom you hire to do work for you. Free wheeling an engine like that proves how and why you could fuck up a ball bearing with a rubber hammer.

[91CoupeMike]

I feel bad for any shop whom you hire to do work for you. Free wheeling an engine like that proves how and why you could fuck up a ball bearing with a rubber hammer.

I do all my own work actually.

That's the first time I've done that, and I know it's not good for it. But curiosity killed the cat and I wanted to know if it would cut fuel.

[91CoupeMike]

It depends on condition dude. Your PIP is calculated by several of your sensors. When your PIP = Max PIP you will get fuel cut whether its at 6250 or 7000 RPM.

You are getting fuel cut

Question. Not arguing just curious.

Why would it go rich after fuel cut? Is that normal?