Cutting out/studdering at 3k-4k
 

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..

Re: Cutting out/studdering at 3k-4k
 

Tps sensor? Or check the fuel pressure reg?

Re: Cutting out/studdering at 3k-4k
 

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

Re: Cutting out/studdering at 3k-4k
 

Have you tested/swapped out coil packs?

Re: Cutting out/studdering at 3k-4k
 

X2 on the coil packs.

Re: Cutting out/studdering at 3k-4k
 

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.

Re: Cutting out/studdering at 3k-4k
 

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..

Re: Cutting out/studdering at 3k-4k
 

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...

Re: Cutting out/studdering at 3k-4k
 

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.

Re: Cutting out/studdering at 3k-4k
 

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

Re: Cutting out/studdering at 3k-4k
 

I have like 8 logs showing perfectly of what's going on. Here is the link to the thread I started with all the logs on the link forum: http://www.dsmlink.com/forums/showthread.php?t=46914

Not sure how to post the logs on here. It says invalid file when I try.

Re: Cutting out/studdering at 3k-4k
 

Wonder if it would attach if you Zipped it.

Dumb question, but what version of Link are you running? I ask because it sounds like it's only doing it under a little bit of load. You say it has no issue when you use light throttle, only when you give it a good bit of gas. Just wondering if you're using V3, and maybe something in your load tables got hosed up.

Re: Cutting out/studdering at 3k-4k
 

I have another coil pack sitting in the garage along with a transistor if the other guy falls though and you want to try a different parts.

Hope its something easy though and not wiring.

Re: Cutting out/studdering at 3k-4k
 

Hopefully you've already checked this, but have you checked compression? I'd think that wouldn't be it though...

Re: Cutting out/studdering at 3k-4k
 

I'm running v3 ecmlink. I tried tuning my a/f in using the load table back before I pulled the head off. I couldn't get a feel for it so I stopped. I went into my previous logs and set all the settings back to original.

iwanta4g63t on here is stopping over tonight and were swapping out the transistor and coil pack

I'm actually about to go check compression right now.

Re: Cutting out/studdering at 3k-4k
 

Cold engine compression 130-125-125-130.

Re: Cutting out/studdering at 3k-4k
 

That's good enough. Nice and even and not ridiculously low.

As for the problem... IDK.

Re: Cutting out/studdering at 3k-4k
 

Swapped out my coil pack and transistor with good known working ones. Same problem.. Gotta be something in the wiring harness. Only thing left that I have changed since I pulled the head off. Gonna take it out tomorrow and see if it's something obvious. If not then I will get a new harness.

Re: Cutting out/studdering at 3k-4k
 

I know ground straps are pretty important but would they cause the car to act up like this? I took off the ground strap from the intake manifold to the firewall, but other then that they are all there from when the car ran great last time. (Battery to firewall, battery to tranny, tranny to frame rail and I think that's about it.)

The car wont even idle anymore either. If I let off the gas the car just wants to die and goes pig rich. If I hold it at like 3k rpm the a/f ratio goes back and forth all over the place. When I drove it yesterday it stayed at 10.0 rich for quite awhile and I could barely even accelerate or drive the car.

I'm gonna go pull the harness out and see if I find something obvious..

Re: Cutting out/studdering at 3k-4k
 

I've always just run one big wire from one of the starter bolts to the fire wall. It wouldn't hurt to make sure your grounds have good solid metal to metal contact.

Have you tried a different ecu with some 550's just for testing's sake?