Fuel Cut: What is it? How do I fix it? [merged]

[Slanted J]

All fuel cut threads are combined here.

I've tried doing a search but to no avail.

I was just wondering what Fuel Cut is. I've heard it tossed around alot, but do not actually know the details behind it. And, naturally, I can gather that its when the fuel is cut off, but when and why.


Thanx,
Jon

 

[oldman]

1. Describe the supposed fuel cut.

2. What are the safc adjustments for the 550s?

3. You need an afpr for the 255.

 

[DSMRon]

It really shouldnt be getting fuel cut inless your gauge is wrong and it really is more then 11psi.. Might be a exhaust leak some where tho.

 

[2gGSX]

If 11 psi nets you the airflow necessary to trigger fuel cut then that's what happened. You should definitely know if it's fuel cut though. As the description goes, "It's like you hit a brick wall"

Based on personal experience, it caused my seat belt to lock up. If it's fuel cut you'll know it, and that isn't caused by the exhaust system.

edit: didn't look at your mod list, sorry. Please refer to Bruce's questions.

 

[ilikespeeding]

Ive never hit fuel cut so Im wondering how the removal of fuel can do that much. To my knowledge, it should only cease the flow of fuel pretty much shutting off the engine.

edit: searching now

 

[oldman]

Ive never hit fuel cut so Im wondering how the removal of fuel can do that much. To my knowledge, it should only cease the flow of fuel pretty much shutting off the engine.

Forget searching, just pull the vacuum line off the wastegate and go for a 3rd gear pull. j/k of course.

 

[delta448]

I think you REALLY need an AFPR. And probably datalogging capability.

I am guessing here, but if you run extremely too rich you could be getting symptoms that make you think you're hitting fuel cut. Stumbling, sputtering, choking, etc.

The 255 will easily overrun your stock FPR, but I don't know for sure why the new exhaust would suddenly make you aware of this already existing problem. WTF

Need more details, especially about the way the car acts/feels when it makes you think you've hit fuel cut. -Also, can you smell gas inside the car?

 

[CanadianTSi]

If you really are hitting Fuel Cut then you have a boost leak, make a tester and fix it.

 

[99gsx0221]

i dont feel like it has a boost leak tho. Because, i get a huge power ban from boost that will pin me back in my seat.

I have a Fuel pump, Fuel Pressure Regulator, SAFCII, and Fuel Injectors that will be installed within the next few weeks. So i dont think ill worry about the fuel cut, because that should get fixed.

I know its fuel cut, because when i hit it, it does feel like im hitting a brick wall like 2gGSX said. Thanks for the help guys, i'll just live with it until i get my fuel system installed

 

[talonTSIDriver]

Is your CEL on? On my 2g Talon when I had my CEL on I would hit fuel cut A LOT sooner than when the CEL was off. Reason for the CEL was a random misfire from the previous owner not using NGK's. But my guess is with the CEL on, more fuel is being added than normal causing fuel cut to happen sooner.

 

[oldman]

I have a Fuel pump, Fuel Pressure Regulator, SAFCII, and Fuel Injectors that will be installed within the next few weeks. So i dont think ill worry about the fuel cut, because that should get fixed.

Fuel cut has nothing to do your fuel system and your ability to deliver fuel, it isn't triggered by fuel starvation instead it's triggered by too much air (think of it as air cut instead). None of the above list items will help you with your fuel cut except some delay with proper compensation with the safc for larger injectors.

CanadianTSI is correct, you need to run a boost leak test big time. Just because your boost gauge is showing full boost during WOT doesn't mean you have no leaks, it just means your turbo is working overtime to make up for the leaks.

 

[oldman]

Is your CEL on? On my 2g Talon when I had my CEL on I would hit fuel cut A LOT sooner than when the CEL was off. Reason for the CEL was a random misfire from the previous owner not using NGK's. But my guess is with the CEL on, more fuel is being added than normal causing fuel cut to happen sooner.

Again, fuel cut is triggered solely by air count, not fuel nor ignition related, what you were experiencing was probably bogging, not fuel cut.

 

[delta448]

I have a Fuel pump, Fuel Pressure Regulator, SAFCII, and Fuel Injectors that will be installed within the next few weeks. So i dont think ill worry about the fuel cut, because that should get fixed.

I thought that since these parts were listed in your car's profile they were already installed.

I am definitely agreeing with boost leak as the diagnosis.

 

[ilikespeeding]

Im still confused as to what your ECU could do to make your car feel like it hit a brick wall?

 

[oldman]

Im still confused as to what your ECU could do to make your car feel like it hit a brick wall?

Imagine boosting 21 psi at 6k and within a split second, nothing, no fuel and no spark, it literally throws your entire body forward, there has been stories of people losing their front teeth on the steering wheel.

 

[ilikespeeding]

Imagine boosting 21 psi at 6k and within a split second, nothing, no fuel and no spark, it literally throws your entire body forward, there has been stories of people losing their front teeth on the steering wheel.

The car still should have momentium from the flywheel. Ive run out of gas under heavy acceleration and nothing like that.

Is it really that bad? I mean, shouldnt there have to be some sort of opposing force to put that much pressure on the car?

 

[oldman]

The car still should have momentium from the flywheel. Ive run out of gas under heavy acceleration and nothing like that.

Is it really that bad? I mean, shouldnt there have to be some sort of opposing force to put that much pressure on the car?

There is a difference between running out of gas during normal driving and running out of gas during WOT doing 20+psi at 6k rpm, is that what happen to you? The opposing force basically comes from the sudden lost of forward ACELERATING momentum.

 

[ilikespeeding]

There is a difference between running out of gas during normal driving and running out of gas during WOT doing 20+psi at 6k rpm, is that what happen to you? The opposing force basically comes from the sudden lost of forward ACELERATING momentum.

That does make sense. I was accelerating pretty heavily...but it was on an old K5 Blazer.

Im guessing that the car completely shuts off. If so, wouldnt you lose powersteering? I dont really think its worth possibly losing someones life over an engine, but thats just me.

 

[oldman]

Fuel cut only lasts for a very short period of time, long enough to give you a good smack in the back of the head to remind you to look at your boost gauge or to perform a leak test but not long enough to shut off the car.

 

[Evo3Talon]

i have a 91 tsi with the following mods most done by the original owner whom i got the car from) 1) small 16g turbo 2) k&n filter 3) magnecore 8.5 mm wires 4) ngk bpr7es plugs and ive put on a stage 2 clutch, fidanza cv axles up front, and a 3 inch turboback exhaust...

now for my dilemma...

when the car IS FULLY WARMED UP...temp guage is a hair under halfway, when im at about 7psi and 3300-3500 rpm, depending on how hard i get on the gas it either bucks/hesitates or i get complete fuel cut...car wants to slam my head into the steering wheel...

at lab in school (uti in exton) ive hooked my car up to the 5 gas analyzer and found several things but nothing explains the fully warmed up condition....im running lean i definately know that..my best a/f reading was 17.4 and ive noticed some carbon buildup around a plug wire where it mates with the coil pack...when the car isnt fully warmed up...the car runs beautifully it couldnt run any better in my opinion...but when its fully warmed up its so annoying....any help is appreciated

 

[Jeremoose]

Have you checked for boost leaks? I'm not sure if a boost leak would fit all the symptoms described, but it's wortha try.

 

[Evo3Talon]

i havent tried that yet though i know vacuum is running right at around 19 in hg i also need to hook up my autometer boost guage and find out what boost im really running cause we all know the stock ones are garbage..

 

[olmytsi]

What do you mean by your best afr reading was 17.4?

 

[Evo3Talon]

at school we have a 5 gas analyzer that also is used as a scope for ignition, fuel injectors and other things its takes the 5 main gasses your car puts out (co, co2, o2, nox, and HC) and calculates your a/f ratio based upon that....the best reading i got was 17.4 and stoich is 14.7 and thing higher than 14.7 is considered lean, and less than that is considered rich.

 

[olmytsi]

N/A and boosted cars are different.

For boosted cars, aka your car, you should not tune any leaner than 11:5:1 a/f ratio at wot. Anything above that is lean at wot. 14.7 is stoich but that's only good for idle and cruise. You definitely want the afr's int he low 11s for wot on pump gas. And peope go in the 12s for wot on race gas.

 

[rocknsnoboarder]

i believe that my car is becoming the victim of fuel cut. If i get on the gas almost exactly 4000 rpm the car bucks and sputters really hard. I researched fuel cut and thought that this was my problem for sure. But every post I read had cars that were more modified than mine. From what I read the stock fuel system should be able to keep up w/ my setup. All of my mods are in my profile but the only major one that I have is an EVO III 16g. Is this enough of an upgrade to be giving me fuel cut?

Also to solve this problem would I be able to get away with using a walbro 190 and my stock injectors. I really don't want to upgrade beyond that because I don't have any logging software.
thanks for the help