Boost Leak or Misfire?

[mr2krazee]

my 1g makes a sudden jerk high up in the rpm band under full boost when doing a freeway pull. i let off immediately if this happens. it does it worse in 1st/2nd under WOT even without full boost, but in the higher gears its only under full boost at about 5500 rpms. so my question is does this sound like a boost leak causing fuel cut? or is this a misfire from bad ignition parts? i have brand new NGK bpr6es plugs gapped at .30 and im pretty much stock (basic mods. no fuel mods) running 12 psi on aftermarket boost gauge with MBC. any ideas would be well appreciated??

 

[gsx_eclipse99]

I had this same problem myself and I did a lot of looking up on it. I was lucky though, I changed my plugs and wires and it fixed it for me. If that doesn't help I would check your cas.

 

[iaintmaci]

There could be several issues causing it to act up. If you think you may have a boost leak, do a boost leak test. You would be surprised what a small boost leak can do.

 

[Tim_I]

you could try gapping your plugs tighter i have mine between .25 - .28. i would check your wires and make sure they are good with no slits or holes in the insulating, do a boost leak test just to be sure, and maybe check fuel filter?. My Tsi was doing this but it went away when i put all my fuel upgrades in.

 

[mr2krazee]

There could be several issues causing it to act up. If you think you may have a boost leak, do a boost leak test. You would be surprised what a small boost leak can do.

thats what ive heard when i search for this problem... alot actually. atm i dont have the means to make a tester so ive been looking for cracks and hard lines and all that jazz. ive also wondered if the MAS is malfunctioning because sometimes i experience an intermittent bumpy idle. I did change the plugs but that didnt make a difference. i may change the plug wires next also because they have been on the car since i got it... i notice if i increase the boost by 1-2 psi it will do it easier in 1st/2nd gear, i put it back down to where i currently run after testing at that level of course. this is a weird problem because in gears 3-5 it will hold full boost most of the time until about 5500 rpms.

you could try gapping your plugs tighter i have mine between .25 - .28. i would check your wires and make sure they are good with no slits or holes in the insulating, do a boost leak test just to be sure, and maybe check fuel filter?. My Tsi was doing this but it went away when i put all my fuel upgrades in.

I will try re-gapping the plugs tomarrow when i have the time and report back. ive thought of trying that but at the boost level i run (12psi) i doubt im getting spark blow out, unless narrowing the gap makes another difference im unaware of...

 

[iaintmaci]

If it does it with increased boost, I would recommend running at only stock boost levels for now. More than likely there are going to be the normal areas leaking: Around couplers, TB shaft seals, maybe some injector seals.

 

[mr2krazee]

i already turned it back down, the increased boost level was simply for a single test run. im running the same 12 pounds i was before i installed my MBC. my wife also reminded me that when i bought the car the PO mentioned that it had a leak near the turbo... totally forgot about that i had to fix the car night i got it, i spent like 5 hours trying to adjust the clutch (so it would quit grinding into gear) after finishing the PO's MC replacement he could not complete due to the clevis pin being a PITA and later i realized it needed a clutch but thats why i didnt recall that until my wife reminded me about it. and now that i think i about it i remember seeing a small amount of hot air come out of the exhaust manifold area when i revved it from under the hood last winter. i believe it was rather near the turbine housing and compressor housing. I'm still wanting to do a BLT as well as check out how the MAS is functioning with a multi meter and some other small diagnostics when i get a good free day here.

 

[mr2krazee]

traded this car off for a 1ga talon AWD so the issue has been solved