WHO CAN DIAGNOSE PROBLEMS?? Bucking at WOT but haulin' at 50%!!??

[rabenne]

I recently started having a problem with my 95 tsi with 6 bolt swap. It bucks hard around 4000-5000 rpm under 70-100% throttle, full boost. it does not buck at all under boost at 50% throttle, and pulls great! I have been watching my a/f ratio with the zeitronix, and my afr is good. I did a boost leak test and couldnt find anything... and it held pressure for 24 seconds after i removed the air source.

I have no idea but this sounds like how people describe fuel cut.

My guesses are:

1. My Walbro 255 is putting too much pressure to the rail under boost??
I have a B&M FPR which is terrible by the way... you cant lower the pressure, only raise it... this means that 53 psi at the rail at idle is unadjustable until friday (when i get aeromotive with import evolutions SS kit).

2. I am pulling enough air through the stock 2g maf that it is telling my ecu that the injectors cant keep up (because it still thinks they are stock) even though I have 550s.

3. This car hates my guts and will never run right!


Please let me know what you guys think... THANKS!


Mods

6 bolt swap
1g big rods
2g pistons
turbonetics t3 t4 50 trim
turbonetics manifold
tial 35 mm wastegate
victory performance o2
megan racing downpipe
apexi straigh back
walbro 255
rc 550 cc injectors
2g maf
1g crushed bov
i think that should cover it, but if im forgetting something just ask

 

[unlmtdndeavor]

my car did the same thing. i had 660's in and couldnt dial them in, after i swapped back to the 450's, the car ran fine. so i would definately look into getting the fuel trims correct

 

[toybreaker]

If the mix stays in the ballpark, I would definately look at the ignition system.

Check the plugs for condition/gap. Inspect the firing ends for uniformity of coloring.

Check the plug wires for resistance. Inspect the ends at the coil, maybe some corrosion is occuring in the coil socket/plug wire connection.

I don't know 2g's that well, but I just fixed a 90 gsx with a bucking issue here locally. In that case, it was a bad cas. And, after that only made it a little better, an ecu fixed the rest. Inspection of the ecu caps revealed spooge on the board, and some damage to the traces on the board. Before the ecu actually fails, it can really do some bizzare things! As a quick test see if you can borrow another ecu for test by substition...

 

[c5chris]

Are you getting a CEL?

My other car did that last week following non-useage for at least a month. It's fine cruising but it idles bad and bucks when I hit over 80mph. Turned out, one of my coilpacks was going bad. I changed it and did additional checking of the ignition components. One of the wires was bad too so I got a set of wires and fresh plugs since I was gonna change all the wires.

Fired her up, idles like new again. I did a spirited canyon run and no hesitation.

 

[majik2k5]

I had the same problem when mine was leaning out at WOT.

 

[rabenne]

wires tested good, plugs are looking good too, only about 1400 miles on them and the wires both... i ordered some new plugs anyway... I also wanted to say that it is definately not lean at wot... the trims are good, and wb o2 says around 11.5 all the way up... so with that said what else could this be?? what about my guesses?

 

[rabenne]

i recently had to have the sensor ground repaired in the ecu as well... its a small trace i think its pin 85... not positive.. but i was thinking maybe something else had messed up as well... i dont have another ecu to toss in.... as for cel's i am getting my normal evap emissions circuit fault p0443, other than that im good..