High STFT Spikes

Most of the time my car runs on the richer side of normal, however there are some circumstances where my STFT will climb to +25.

If I'm very light on the throttle like driving through a crowded parking lot, STFT will slowly climb to +20 or more and will stay there until I let off or give more gas.

If I'm doing a partial throttle pull, like 10 psi in 4th or 5th gear, sometimes when I let off the gas it feels like the car falls on its face before my foot is all the way off the pedal and I see a spike of around +25 STFT. This is the part that scares me.

Also, my throttle is a lot harder to control in higher gears, the car will go from -1 to around 7 psi at virtually the same throttle position and vice versa. And during normal driving the car is a bit jerky when getting off and back on the gas.

 

You could have a leak somewhere between the maf and intake manifold, have you checked for leaks?

What's your LTFT at idle and cruise?

Edit: also what rpm and gears is this happening in?

 

I've checked for leaks a number of times and can't find any.

LTFT is always between 0 and -7

The STFT spikes where I'm finding it hard to control the throttle usually happen in 5th gear during light pulls. I usually wait till just under 4k rpm to boost in 5th

 

well thats good +/-5 is ideal number for LTFT 7 is where we start to talk about having a leak and certainly by 10 you should be looking for a leak.

have you boost leak checked specifically? I had one that didn't show until I leak tested, how old are spark plugs? gapped to 0.026-0.028"? may be worth cleaning the maf sensor, perhaps even throttle body.

Mileage on car? have the injectors ever been service and seals been replaced? ever done an intake valve cleaning?

 

LTFT being at -7 is probably because I had my injectors cleaned shortly after my PD tune was completed. I showed logs to the tuner and he says the LTFT is nothing to worry about.

For leak testing all I've done is have a friend blow vape clouds into the intake, intake manifold and other random vacuum lines. everything seemed air tight although I'm sure there's better ways to check.

Spark plugs are gapped at .025 per tuners instructions and are only 6k miles old. The car only has 67k miles and I've cleaned the valves, injectors, throttle body, rebuilt HPFP and replaced o2 sensors, compression is also good. I also have a slightly sputtery idle that may or not be related and I've done pretty much all the recommended maintenance and then some to try and fix to no avail.

 

How old is your battery? If it's starting to die it can really screw with low throttle performance

 

battery is just a year or two old, I replaced it when the original battery started to die

 

I was thinking bad injectors, until I continued reading. It seems like you've done all of the maintenence to rule those out.

What downpipe?
STFT tend to fluctuate to both extremes, and your LTFT seems reasonable at -7%. The awkward throttle response may or may not be related.

 

ATP catted DP, I know I usually should not be concerned about short spikes in STFT but they seem to consistently happen when I'm in boost with partial throttle which worries me.