Issue has been popping up with random cuts/hesitations at WOT. I've looked for similar issues, but it's not the common ones at 3800rpm or the "invisible redline" where it simply stops revving past a certain rpm and completely cuts out. I can go to redline just fine, but along the way for a split second I'll get cuts in power, maybe 2-3 times before the next gear, as if I were jabbing off throttle randomly. I suspect either bad spark plugs or injectors, potentially fuel pump, but am not sure. I'll see if I can post a video here tomorrow to clarify.

 

Hello,
I had this same issue with hesitation but only at WOT at high RPM.
For me, it turned out to be the spark plugs. It took me ages to figure it out because I was only changed them 5000km before that so I couldn't believe they had fouled already!
I've learned since that 13B does not like to idle for long periods. It ruins spark plugs so quick with carbon! I used to let my FC warm up fully before driving. Now I just let it warm for 30 seconds and drive off. Haven't had the same issue since

 

Wow that sounds exactly like it... I also have fairly new spark plugs, it only happens at high rpm at WOT, and I used to let my car warm up fully before driving. I'll check the plugs first then

 

Yeah its probably worth buying a new set of plugs just to rule out any issues with them.
you'll use them eventually anyway even if it turns out to be something else causing this issue.

I know the throttle position sensors can cause this kind of thing too so maybe thats another thing to check. There's a process for measuring the resistance of them and making sure its within spec when WOT.

Spark plug wires could also maybe cause an issue like this if they're really old

 

is this an S4? S5? Turbo? non?

 

S4 base

 

i would start with free, and check the spark plug wires. they should be under 16k OHM's resistance, and new is like 8k.
the higher the resistance, the less power is available to fire the plug. if the old plugs have more than ~5k miles on them, you might replace them.

then i'd make sure the battery connections are clean, and tight. especially if you have some aftermarket cable ends, they wear out

after that its either fuel or exhaust, take your pick. with the exhaust you want to look for broken converters, basically.

fuel you can either change the filter, and the pump sock, or test fuel pressure, not sure which one is easier

 

Trailing plug wires both gave 5k ohms, leading both gave 8k ohms. I'm no expert on spark plugs but I checked both trailing and they seem good to me? but for all I know they could be completely toast. cba to get pics of the leading plugs as well because it started raining (no garage space to work in). My battery connections are pretty terrible, they're clean but old and very chewed up, but work. If everything else looks good I'll just have to get new terminals which I should do anyway. I don't have cats so I don't think it's that. Will probably have to check the fuel pressure/pump next if the plugs are all good.

 

resistance testing the wires won't show issues with burn through of the boot or wiring insulators. close inspection of plug wires is needed for that. those plugs look fine.