Weird boost issue?

[Turbwhistle]

So for the past few months, i have been having almost a fluttering while under boost. I can be just cruising around in 4th or 5th, and then mash on the pedal, and all i get is a fluttering of my boost from between 6psi and then back to around 15psi. I have no codes, so i have no clue what to check.

I was thinking it is my diverter valve, but i was told it isn't. My mods are ebay tp, air box mod, Giac flash, rac tech fmic, 710n, and thats it. My car is a 99 1.8t aeb. I read that it could be the gapping of the spark plugs, messed up maf, over boost, or a boost leak. So, i do not have any codes, so where should i start? Any other things i should check? It is a little bit frustrating when you are trying to accelerate and you get pretty much nothing.

Thanks in advance.

chris.

[Turbo Nerd]

I'd start with a boost leak test and change the plugs with BKR7E gapped to .026 to .028 (about $2 a plug). You really shouldn't be mashing on the gas in low RPM while in high gear.

[Turbwhistle]

I will check for leaks later, everything on my boost gauge seems right, 20psi of vac, and 16psi boost.

[coolgraymemo]

Does in consistently go 6-15-6-15...? If so, that is sign of a bad N75.

If not, it is most likely a boost leak.

[Turbwhistle]

Yea, it is pretty consistent on the drops, when it happens. It doesn't occur often, but when it does its annoying. I am going out in a few, so i will verify the drops, i was thinking o getting a n75j anyway

[offroader1006]

I use BKR6E's gapped to .028.

the BKR7E's are a higher heat range and can foul quicker on a stock-mild engine.


This sounds exactly like what I get when I need to replace my plugs. If one has misfired severly enough, re-gapping may not help, as the spark has started leaking through the insulator.

A set of plugs is cheap insurance before you start fault tracing to the moon.

[offroader1006]

You really shouldn't be mashing on the gas in low RPM while in high gear.

This is one of the best ways to find faults in your secondary ignition circuit that would otherwise be hidden by normal driving.

I do this routinely to check for misfires under heavy load, and in a properly functioning car, should not cause any issues.

[Turbwhistle]

Well i checked for boost leaks and found nothing major. I have yet the check my spark plugs, but they are fairly new, i just got them like maybe 2k miles ago. I also run BKR6E's, and they were gapped to .028.

[offroader1006]

Well i checked for boost leaks and found nothing major. I have yet the check my spark plugs, but they are fairly new, i just got them like maybe 2k miles ago. I also run BKR6E's, and they were gapped to .028.

I would check them regardless of age. I never let an outside issue affect my fault tracing. It can lead you away from obvious solutions.

It could be a coilpack as well.

[MadAudi]

Sounds like an N75 valve. It will not always throw a code for this kind of behavior.

HOWEVER, I have seen the waste-gate *door* start to come loose on these turbo's and cause the behavior your are showing. You have to pull the down pipe to check. Sometimes you can just weld it back on and your set. Otherwise you need to change your exhaust housing.

[Turbwhistle]

Yea, i will end up picking up a new n75 eventually, its not to big of a deal currently.