Loses power 3-4K rpm in boost

[AndrewC]

I just got my first 2G GSX with minor mods. FMIC, recirculated bov and cat back exhaust. I’m having an issue that affects just driving the car. Basically even just a tiny bit of boost between 3K-4K rpm the car loses all power. I can be building 10psi and just goes nowhere like I’m dragging the brakes. But I can drive through it no problem with no boost. I just put spark plugs in it and gapped to .28. After 4K rpm all boost hits and pulls good throughout the rev range no problem. The car has no boost leaks, good compression and turbo is fine.

 

[ThunderChild]

Does the car have any tuning equipment? Have you done a boost leak test?

 

[AndrewC]

Does the car have any tuning equipment? Have you done a boost leak test?

I have yet to do one myself because I don’t have the equipment. And as far as I know of it doesn’t. I have yet to look at the ecu either if it could be a aftermarket . Because the previous owner said the car was on 15psi on a MBC but removed it.

 

[ThunderChild]

I would recommend a BLT, check plug wire condition, fuel filter replacement, fuel pressure check (dynamically during issue would be great, but difficult) and then an ECU inspection. Might consider trying a tighter plug gap as well, mine is .024" on a 14b to run correctly.

Almost makes me think it's a maf issue with the way it falls on it's face, but tough to say. I'd recommend getting some way to tune/log and a wideband if you don't have one already so we can see what it's doing during the bog.

If you can fill out a profile too so we can see the mods done, that would be helpful.

 

[AndrewC]

I’m thinking it’s some sort of fuel issue. I’m trying to get a wideband and see what happens because it’s almost the same thing my 240 did that it pulls harder in half throttle than wot because it ran lean. Im also thinking that it’s because the quality of gas I’m using, I had a 1G tsi before on 14psi and would buck under wot but after I put a different brand in it stopped that’s what I’m thinking. I have an safc I can pull out of my 240 since I don’t need it anymore but I need a wideband as well.

 

[motomattx]

You need to log knock counts, the 2g seems to be very sensitive to phantom knock.

 

[AndrewC]

That’s what I’m thinking is phantom knock. But I did more digging on the car and the plugs I just put in are BLACK and I never noticed but smokes black hard when you rev it so this thing is running rich. I removed the air filter to let more air in and the problem got less aggressive. I can only think the car was on 15psi, the person I got it from removed the MBC sand set it back to 10psi and said it runs rich. I’m starting to think it was tuned on 15psi. I’ve been looking around and can’t find anything as far as a piggy back system. Stock injectors from what I can tell and pump. I haven’t been able to take the ecu out and look at it but from what I can see it looks original. Is there a way to flash tune a stock ecu? If the car has dsm link would I only notice from opening it up?

 

[rEclipserGST]

Do a boost leak test. Small air compressor from Home Depot or Lowes. You can make your own tester or Buy one.

Yes, you would have to remove the ecu and remove the screws to verify what kind of ecu you have.

10 to 15 psi is not that much of a difference. No one is going to tune a car for 15. He "removed the manual boost controller" for other reasons.

Replace the plugs. Replace the wires. Put the air filter back in the car before you ruin your turbo from debris.

Buy an AEM wideband or LC-2 wideband. Do some research. Let us know how many boost leaks you find.

 

[motomattx]

You can also check the coolant temp sensor, the one for the ecu can go wacky and cause these kinds of things.

 

[cbilmer]

It does sound like you're with spark or fuel.
I recently had VERY similar issues with my 3000GT VR-4 (very similar platform) and it ended up being the coils. They don't age particularly well, and these cars are getting old. I got them for about $20 each on Rockauto.