Fuel pressure too high after WOT

[SlamChop]

2010 ms3 here, cpe tmic, htp 3.5 intake, Autotech internals, hks bov, corksport dp, custom Catless cbe, dizzy tuned, was running 1:3 e85 ratio mix then switched back to 93 once problems started happening. So to make a long story short (I will provide answers to any questions anyone has) I installed my htp intake replacing a crappy one that was on the car when I bought it thinking that it would fix my fuel trims because car was running lean. After I replaced it nothing really changed. Found out my maf sensor was bad so I replaced that too, trims were fixed but i noticed I was having some stuttering for a few seconds when I would let off the gas. I started paying close attention to my Hpfp act pressure, saw that it was consistently too high like between shifts, when engine was braking, things like that. Seemed the pressure would get stuck higher than it should be and my car would be slightly boggy. I then took apart my Hpfp to inspect everything and found a little (black death). Took everything apart ( including Hpfp housing) and soaked it in b12 chemtool. Everything was then clean and I re installed. Everything seemed to be okay like between shifts and engine braking the psi was normal. So I decided to give it a wot to see how things were and I hit my target fuel psi and boost psi but for 10-15 seconds after wot ( now in 4th gear ) my fuel psi is stuck at 900+ without touching the pedal, if I touch the pedal at all to shoots up to 1700-1900 with any amount of acceleration. While the lressure is high like that my car stutters and basically has no power for that 10-15 seconds. Not really sure what this could be. Maybe just my internals went bad and don’t slide as smoothly as they should? I have no idea

[Thor Hammer]

Nice wall of text. Makes it hard to read. FYI.

When you changed intake was it same diameter as before? If not, you need to get re-tuned/MAF calibration.

Letting off the gas you will see dips in pressure. 17-1900 is not too high. Its normal.

[Jeff23spl]

1700-1900 with pump internals seem normal to me...stabilize around 1750 under wot and spike back a bit above when you drop de pedal.
When i put back mine, i do remember it take few km to get it stabilized.

While engine breaking i think mine is about 450psi and it goes back above 1000 very quickly to reach target as soon as i ask for some load.

have you confirmed that pedal reading read correctly ? I don't know if a special throttle table could affect this....

Why not just put back a stock tune with your actual maf cal (And map if not oem) to see if it change anything?

Is your AFR ok during that time? it should fall to 29 when you let go the pedal but get back to stoich or target as soon as you go back in load....If AFR is ok, there is no reason the fuel pressure make the engine goes bad

IMO Bad pump won't rise pressure but instead keep it lower than expected....it would be the release/spill valve in that case maybe
I remember some thread here about ethanol problems but you will have to search.

Is your o2 seem to read ok ?

I would go back to basic since your car seem to go bad from the beginning...
Check compression
Timing chain
new spark plugs
Leak test
Maf cal again and confirm your open loop afr vs target

[SlamChop]

Originally Posted by Thor Hammer Nice wall of text. Makes it hard to read. FYI. When you changed intake was it same diameter as before? If not, you need to get re-tuned/MAF calibration. Letting off the gas you will see dips in pressure. 17-1900 is not too high. Its normal.

I did get a re tune when I got intake

[SlamChop]

Also, Anytime I throw it into neutral and let the RPMs drop all the way down to idle it drops below my normal idle and my actual afr drops to 8-9 and then bobs back up to normal

[Thor Hammer]

What about Bob?

[SlamChop]

Originally Posted by Thor Hammer What about Bob?

He’s a nice fella

[SlamChop]

What could cause my afr to dip like that?

[Jeff23spl]

a bov maybe

[SlamChop]

@jeff23spl how would a bov cause this?

[shamie]

If you are VTA.

[Jeff23spl]

as said above, when it open and flow outside, the maf continue measure flow and call to add fuel but that flow isn't going inside the engine. This is why a full VTA is fun but a BPV is better

[SlamChop]

Interesting... I never started having the problem until the new intake.. I did get a new map sent to me for it but could it be tuned for? Like I’m just confused on why it has started happening all of a sudden. I know it’s better for the car to go bpv I still feel like it should atleast be as smooth as it used to be. Maybe like a month ago