WOT + boost = bucking like crazy

[AEB A4]

Ok, let me start by saying whats done to the car.

1999.5 1.8T manual quattro
k04 + pc16 software @ 15lbs max due to slipping clutch
MBC (no n75)
Forge splitter diverter valve
Borla exhaust 3" testpipe and a bunch of other little things

Heres the problem, when i get on the gas and reach in the higher boost levels arond 15ish it start bucking like crazy. Total loss of power and the boost is everwhere. I know the forge splitter is adjustable so maybe i have it adjusted too loosley?? or maybe my manual boost controller is effing things up? its really annoying and i dont think its a bad tune due to someone before me running it fine on there same exact vehicle. Help would be greatly appreciated. thanks

[onemoremile]

Sounds like boost is leaking somewhere. The s4 did this years ago. At part throttle or casual driving it was fine but if you floored it the car would buck and smoke a bit. It turned out the the throttle body boot had a small tear in the underside of it and would stay closed until the pressure increased enough to leak some charge air. This causes a huge loss of power. Then the ECU would spin up the turbos to make up for the loss and make big power, then leak, no power, spool up, big power, leak, etc...

It didn't take much of this before one of the turbos overspun and popped.

[AEB A4]

ill have to look for boost leaks. Could the diverter valve also be a problem in this. Could it be prematurly opening and closing causing the bucking and surging of power??? Another thing i though of was if my MBC is shot or effed up it could be opening and closing the wategate flap causing the power surging. Ill swap both the MBC and DV and see if it helps at all. I just hope i dont have to hunt down a boost leak. Would a boost leak make it buck the whole car hard because thats what happening?

[NewFisher]

MAF???

[AEB A4]

i disconnected the MAF and ran it ran like poop and started to do the same thing. Ofcourse it wasnt going to run right with the MAF disconnected !! I got vag com so if anyone can give me Blocks to look into that would be great. Checked for misfires and there are none, so thats good news. maybe next will be to throw in a regular DV and see if that fixes it although that shouldnt be the problem. HELP

Can you do a boost leak test through Vag-Com ?

[pinky]

how do you have the splitter set?

[ladedruck]

Ok, let me start by saying whats done to the car.

1999.5 1.8T manual quattro
k04 + pc16 software @ 15lbs max due to slipping clutch
MBC (no n75)
Forge splitter diverter valve
Borla exhaust 3" testpipe and a bunch of other little things

Heres the problem, when i get on the gas and reach in the higher boost levels arond 15ish it start bucking like crazy. Total loss of power and the boost is everwhere. I know the forge splitter is adjustable so maybe i have it adjusted too loosley?? or maybe my manual boost controller is effing things up? its really annoying and i dont think its a bad tune due to someone before me running it fine on there same exact vehicle. Help would be greatly appreciated. thanks

do you have the injectors for the pc-16 file? they are different. And a bad mafs will run a lot like no mafs on the early stuff so you may still need a mafs.

[AEB A4]

im not too sure how many times the splitter is turned since its ben in the car for a while and i changed it a few times. Is there a way to set it properly ???? When it was first set i turned it until i didnt hear the clicking of it anyome like the instructions said but now it "clicks" randomly


yes, i have the 315cc injectors that are used on the pc-16. As for the MAF , connected ran alot smoother and much better overall compared to it disconnected. This leads me to believe the MAF isnt the problem. Dosconnected it ran very rough at idle unlike when connected but at WOT they both buck. Also, it dosent always happen at WOT, sometime the bucking happpens in partial thottle in high boost. Should i check the air fueld ratios via vag-com and see if there is a fuel problem????

[ladedruck]

I guess I was trying to say if it runs bad then unplugging the mafs doesn't tell you much. It has to have a good mafs to run well. One reading 10% low will throw it off. I would say if you don't have any boost leaks then logging the mafs and o2 sensors with the magic vagcom would be my next move.

[AEB A4]

ok, thanks for the help. Does it matter that i run a test pipe? I put some washers in the rear 02 sensor to move it out of the main stream of air but never got the "anti-fouler"

No check engine light has come on but did pull 2 codes yesterday. one for n75 being disconnected and another for the MAF being disconnected, other than that no codes

[Militant-Grunt]

ok, thanks for the help. Does it matter that i run a test pipe? I put some washers in the rear 02 sensor to move it out of the main stream of air but never got the "anti-fouler"

No check engine light has come on but did pull 2 codes yesterday. one for n75 being disconnected and another for the MAF being disconnected, other than that no codes

Rear 02 is purely for emissions, test pipe has nothing to do with it. I'd log the car to see whats going on.

[AEB A4]

ok, im a noob to VAG-COM so ill search and try to figure out what each block is suposed to be at. Anything i should look for through vag-com in perticular???? Already checked for misfires, what other blocks should i be looking at?

[AEB A4]

ahhha, can it be my ICM effing things up and causing this. right now it is hanging loose int he engine bay since i have a cone filter and no where to mount it. did i just fry it and now its giving me problems??? help ?

[Poopie]

possibly. do you have any codes?

[AEB A4]

only codes that came up where n75 (because its disconnected and im running a mbc) and thats it.

[turboquattro068]

I had a similar problem and it was my ICM, I have two of them, bought two on ebay for a decent deal, figured why not since it was cheap and it could possibly happen again in the future. Let me know if you want to buy my extra, I"ll give you a decent deal and I can ship it out tomorrow for ya. I"ll PM you my paypal. Just PM me or email me at [email protected]. Emails are better for me