Cutting out/studdering at 3k-4k

[4g63tcrazy]

So I can't figure this out.. When driving the car and giving it some throttle to get the turbo spooling, the car will studder really bad, wideband goes full rich, and I get anywhere from 10-15 counts of knock. It happens anytime I'm over 25% throttle. It will also do it just when I free-rev the car. At the same RPM. It does it right at 3k to 4.5k and after that it rev's smooth all the way to 8k.

I have tried adding a bunch of fuel, taking away a bunch of fuel. Taking away timing and zero'ing everything out. Nothing made any difference.

I swapped the CAS 180* out and car still free-revv'd the exact same.

I put the CAS back, installed new spark plugs. Gapped them at .24 and changed nothing.

Did a boost leak test. My BOV gasket leaked slightly and the throttle body leaked slightly. Fixed both of those. Didn't change a thing still.

It feels just like the car is misfiring when it does it. EXACTLY like a misfire. Then it just goes away and rev's fine to 8k. What am I missing? I feel like I've checked everything..

I would attach a log I did of when it happened but it says invalid file..

[93gtpeater]

Tps sensor? Or check the fuel pressure reg?

[4g63tcrazy]

TPS works fine. Base fuel pressure set to 37psi.

[goodhart]

Have you tested/swapped out coil packs?

[123abc]

X2 on the coil packs.

[Halon]

I would first say you need to re-gap your plugs if you are truely at .24", but I'm assuming you meant .024" :) Then I'd say try swapping coil packs, transistor, and plug wires. If it still continues, maybe a different MAS.

So when it's studdering, is it right when your turbo is starting to spool up? If so, what would happen if say you were just cruising at 5k RPM's, then gunned it and the turbo spooled up quick. Does it sputter then, or only at that RPM? Guess I'm trying to figure out if it's really an RPM based issue, or if it's based on when the turbo spools up.

[4g63tcrazy]

Ok, I swapped out MAFS and still does the same thing.

I swapped my old 950's back in cause I thought maybe an injector was stuck open since my car stays full on rich ALL THE TIME now. It wont even run unless I keep on the gas.

If I rev the car to 4.5k-5k and gun it, it doesn't cut out. So it's definatly an issue around 3-4k. But man does it haul ass :)

Spark plugs are brand new. (gapped to .024) Plug wires are fairly new Magnacores.

The only thing left is the coil pack and transistor. I'm gonna have Jake (iwanta4g63) stop over tonight and swap those parts out and see what happens.

If that doesn't fix it then there is only one thing left. The wiring harness..

[123abc]

If that doesn't fix it then there is only one thing left. The wiring harness..

I'd feel for ya man if it's a mistake in your wire harness. Mines has been fine so far, but I have yet to actually do a pull. I'm trying to get some form of exhaust done for it so it's not so damn loud...

[4g63tcrazy]

Haha yea it's been in the back of my mind this whole time. Cause all I changed since the car ran last was valve springs, valve stem seals, resurfaced head with a composite headgasket, and cleaning up the wiring harness. So unless a sensor decided to go bad within that amount time the only thing it could really be is the wiring harness. My car ran perfect before I had to pull the head off.

[Kevin 1G Drummer]

Do you have any logs of what's going on at that rpm?