fuel cut possibly??

When I hit full boost(about 14psi for now) after a few seconds its like I'm getting fuel cut or something cause the car just jerks and kind of acts like I have a boost leak. I just changed my plugs with some NGK BE7RES gapped at .028 like chunkymilk instructed and that didnt solve anything. Any ideas as to what might be the problem?

When I hit full boost(about 14psi for now) after a few seconds its like I'm getting fuel cut or something cause the car just jerks and kind of acts like I have a boost leak. I just changed my plugs with some NGK BE7RES gapped at .028 like chunkymilk instructed and that didnt solve anything. Any ideas as to what might be the problem?


I'm having the exact same problem.

I'm having the exact same problem.
I'm glad I'm not the only one. At least now someone knows what I'm talking about.

That sounds strange but probably not fuel cut because I remember my eclipse with the evo III and no fuels mods topped out at 16psi with no problem. From what I've heard about fuel cut, it's like you just hit a wall while boosting. Have you changed your plug wires also? If you did have a boost leak the car would definitely jerk a lot, I would check again for cracks and holes in your piping.

I know I don't have a boost leak I'm almost 100% sure. I just can't figure out what it is.

I just changed the plugs and wires and I've smoke tested my entire intake/exhaust system granted its not pressure testing but all my couplers were just replaced with silocone so those are good. I can't think of anything that could cause this
EDIT: Also if you where to have a boost leak wouldn't it be noticable more than just at full boost, or could it just be a leak that only leaks at full boost? I think I might have just answered my own question

I just changed the plugs and wires and I've smoke tested my entire intake/exhaust system granted its not pressure testing but all my couplers were just replaced with silocone so those are good. I can't think of anything that could cause this
EDIT: Also if you where to have a boost leak wouldn't it be noticable more than just at full boost, or could it just be a leak that only leaks at full boost? I think I might have just answered my own question


I've had a boost leak before, and when I would try to boost I could hear the turbo spinning but I wasn't getting any boost. hence boost leak. I mean that was a major one but on a smaller scale I think it would be you wouldn't be getting as much boost as normal.

I'm getting good boost until 14-15psi, as soon as it hits that the car just fucking jerks like it's stuttering or something. Just like yours

It makes me think fuel cut.

I've had a boost leak before, and when I would try to boost I could hear the turbo spinning but I wasn't getting any boost. hence boost leak. I mean that was a major one but on a smaller scale I think it would be you wouldn't be getting as much boost as normal.

I'm getting good boost until 14-15psi, as soon as it hits that the car just fucking jerks like it's stuttering or something. Just like yours

It makes me think fuel cut.
yep, same thing. I think we might need Kevins knowledge lol

you sure your car isn't cold?

you sure your car isn't cold?
umm, yes

Yea my car seems to jerk like that only when the engine is cold. Than again, it doesnt do it at full boost, just basically in between 1 psi and 13psi(full boost) when its cold. Im really curious about your problem though. Kevin's knowledge would def be appreciated for this.

My car acts the same way. Only under full boost after about three seconds. Drives me mad! I've always thought fuel cut, but I want to fix it asap.

Fuel cut won't act like a stuttering, as someone mentioned. It just straight shuts the fuel off, for a couple seconds. Of all the boost leaks I've had, none really caused a stuttering effect, while 99% of the time this is ignition related. So I would stick with ignition for now. The plugs sound good. I know you said you changed the wires, but there are only two wires that I trust. Stock (ran them deep into the 11s ;) ) and NGKs. I've seen just about every other type fail on install, right out of the box, especially if they are not designed specifically for a turbo car. NT wires don't have to do 10% as a good a job as turbo motors wires do. The compressed fuel air mixture is much denser than what you find in an NT motor, it can be tougher to get a spark through. If the path of least resistance becomes out the side of the weak ass jacket or boot, you're all done. Magnecores are technically a trusted brand meant for our motors, but I've had too many of them shit the bed as soon as I install them.

If the description was a little different I might suspect fuel cut if the temperature where you are is very low. Air density goes up of course, and the mas reports this to the ECU as expected. You will hit the limit at a significantly lower boost than you did in the summer. Hard to say if 14 psi is the magic number, since there are so many variables in different setups. All the talk I go into about changing airflow vs boost applies here as well.

If plugs and wires dont do it, I usually try to borrow coil packs and ignitors to go one step further. I always have an extra ECU closeby as well, just in case that would do it. Only then would I move away from ignition related troubleshooting and try other things. A boost leak test certainly is easy to do, and I recomend to do them no less often than you would change your oil anyway, so do that if you havent already anyway, regardless of wether or not we exepct it to be the source of the stuttering.

Just put on stock wires, and yes its pretty cold here(minnesota, averaging 30 or less during the day)

Yeah, my Talon doesn't exactly hit a "wall" like you said with fuel cut. It stutters. I'll definately check the ignition system, thanks.

i wood recomend and hks fuel cut defencer, this shud stop fuel cut, completely or u can ajuste it according to how u drive. this shud stop ur fuel cut when at full boost. though fuel cut wont cause ur car to shudder as u say it does, but this may help

All of those fuel cut defencer things are worthless on our cars, and I would advise against them if you want to keep your motor.

I'm hitting fuel cut in third gear onwards at WOT. Running stock boost and stock a/f on the EvoIII16G (no external boost control; BCS is in place, 2.5" catback).

Boost will hit 16 psi, stay there for a few seconds before "jerking" up to 22 psi. I don't know why I'm getting creep; the wastegate size should be adequate for stock boost. The car jerks like crazy, and I can't really floor it as much as I'd like.

The question is....it is fuel cut, isn't it?

I don't know why I'm getting creep; the wastegate size should be adequate for stock boost.

I may be misinterpreting what you are saying, there are two ways to take this statement. You either mean "stock boost" as a low value compared to what many poeple like to run on these cars, or you meant to say it's a high enough boost that creep shouldn't be an issue. Because people ALWAYS get this concept backwards, I'm going to assume you meant it backwards. :) If you didn't, don't take offense, I can never keep track of everyone's experience and knowledge level, and at the least this may help some of the others that may not understand all this yet at this point in thier learning process. This is more of a general explanation, just because the oppurtunity presented itself. ;)

There is a reason this is widely misunderstood; it's quite counter-intuitive. Many poeple think that you need a BIGGER wastegate to run HIGHER boost. And WG manufacturers and vendors don't help the situation at all when they rate a WG with some power level, which is absolutely ridiculous... In fact, you need a BIGGER wastegate to run LESS boost. To illustrate the example, think of what a WG does. It bypasses the turbo to limit compressor rpm and control boost. If you wanted to run a turbo at the maximum possible boost or flow it can support, you wouldn't need any WG at all. A very small one will suffice to run it close to it's limits. If you wanted to run a large turbo at 2 psi, you would need a huge WG to bybass the majority of the engines exhuast gas.

All that being said, understand that every single turbo setup out there will creep to some degree, because no turbo or turbo system has a wastegate as large as the exhaust itself (in that it can bypass ALL of the exhaust gas around the turbo. They will all creep. What determines wether or not you see the creep is what boost level you have set the system to. If the creep level is lower than the set boost level, you will never see it (and incorrectly assume there is no "creep" with this turbo or system most likely). If you are trying to set boost below what the creep level is, you will see the creep and then have a choice to allow it to do it's own thing or do what it takes to get it under control. A EVO3 16g with an internal gate will likely have a creep point over 16 psi, but a lot of this depends on the exhaust. I Think in your case Shpyder you run a relatively stock exhaust (The catback perhaps?) which should reduce the boost creep level. I would expect it to be below 22 psi, but as I said there are many variables. I still think the description of fuel cut isn't really present here, but poeple choose to describe things in different ways. At 22 psi on the evo3 16g I would certainly expect to see fuel cut if nothing has been done to remove it (DSMchips, TMO, or DSMlink) or raise the point its triggered at (bigger injectors and AFC). Getting boost under control would be the first step to take IMO. COlder weather makes creep worse too, so it may be worse now that it was a couple months ago. Some porting of the turbine housing has always fixed creep in my experience, and I talk a bit about what I do on my site.

Haha, Kevin, I would never take offense to anything or anyone who corrects me/ helps me out. As Socrates said, "The greatest knowlede is to know that you know nothing." That's why I'm on the forums.

Though I understand what a wastegate does, I didn't say what I meant correctly at all :banghead: haha, sorry. By "stock" boost, I meant that the boost was regulated by the BCS and was set at "factory specs"; and that there was no aftermarket boost control. I see how easy it is to confuse the wastegate issue once you explained everything. So, if you have a massive turbo that flows lots of air, and you run it at 5 psi, you need a larger wastegate to help bypass the extra air coming through to see that it doesnt enter the turbo. Which means that at high boost, you need all that air into the turbo, so you bypass less, and hence a smaller wastegate will do. (I hope I got all that remotely correct!).

I'll have the greedy profec installed soon then. I do run a catback, like you said. To me, with stock a/f at 22 psi, I seem to be starving the cylinders, and the sharp jerking would make sense to me as fuel cut with this turbo (car loses power with a loud "thud" sound, operates normally only once I ease of the throttle). I hope its fuel cut, and not another mystery DSM problem!

I may be misinterpreting what you are saying, there are two ways to take this statement. You either mean "stock boost" as a low value compared to what many poeple like to run on these cars, or you meant to say it's a high enough boost that creep shouldn't be an issue. Because people ALWAYS get this concept backwards, I'm going to assume you meant it backwards. :) If you didn't, don't take offense, I can never keep track of everyone's experience and knowledge level, and at the least this may help some of the others that may not understand all this yet at this point in thier learning process. This is more of a general explanation, just because the oppurtunity presented itself. ;)

There is a reason this is widely misunderstood; it's quite counter-intuitive. Many poeple think that you need a BIGGER wastegate to run HIGHER boost. And WG manufacturers and vendors don't help the situation at all when they rate a WG with some power level, which is absolutely ridiculous... In fact, you need a BIGGER wastegate to run LESS boost. To illustrate the example, think of what a WG does. It bypasses the turbo to limit compressor rpm and control boost. If you wanted to run a turbo at the maximum possible boost or flow it can support, you wouldn't need any WG at all. A very small one will suffice to run it close to it's limits. If you wanted to run a large turbo at 2 psi, you would need a huge WG to bybass the majority of the engines exhuast gas.

All that being said, understand that every single turbo setup out there will creep to some degree, because no turbo or turbo system has a wastegate as large as the exhaust itself (in that it can bypass ALL of the exhaust gas around the turbo. They will all creep. What determines wether or not you see the creep is what boost level you have set the system to. If the creep level is lower than the set boost level, you will never see it (and incorrectly assume there is no "creep" with this turbo or system most likely). If you are trying to set boost below what the creep level is, you will see the creep and then have a choice to allow it to do it's own thing or do what it takes to get it under control. A EVO3 16g with an internal gate will likely have a creep point over 16 psi, but a lot of this depends on the exhaust. I Think in your case Shpyder you run a relatively stock exhaust (The catback perhaps?) which should reduce the boost creep level. I would expect it to be below 22 psi, but as I said there are many variables. I still think the description of fuel cut isn't really present here, but poeple choose to describe things in different ways. At 22 psi on the evo3 16g I would certainly expect to see fuel cut if nothing has been done to remove it (DSMchips, TMO, or DSMlink) or raise the point its triggered at (bigger injectors and AFC). Getting boost under control would be the first step to take IMO. COlder weather makes creep worse too, so it may be worse now that it was a couple months ago. Some porting of the turbine housing has always fixed creep in my experience, and I talk a bit about what I do on my site.