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]

You're welcome, glad to see you got it resolved.

 

[andymoraitis]

Fuel cut has nothing to do with your fuel system or what pump you are running. It is airflow related. You flow over a certain amount of air through the mas and you hit fuel cut.

I stand corrected (really). I got around my issues by installing a 95 EPROM ECU with fuel cut removed in the chip.

 

[spyderturbo007]

You can delay fuel cut by getting larger injectors (let's say 550cc's) and an SAFC-II. This will allow you to drop the airflow as seen by the ECU, which compensates for the larger injectors and keeps the ECU from cutting your fuel.

 

[JessesTalon]

remember 15psi is MUCH different from a stock turbo to a b16g... you will be flowing alot more which is why your fuel is getting cut.


turn the boost down to 10 and you will prolly feel faster and not hit fuel cut

 

[94EclipseGST]

I agree with spyderturbo. You need to upgrade your injectors and get some tuning device. I made the stupid mistake of upgrading my turbo before updating fuel components. My car was slower than stock and made me sick to my stomach.

Now, after some 550's, MAFT, Walbro 255 that Big 16G is awesome.

 

[doug]

Fuel cut has nothing to do with your fuel system or what pump you are running. It is airflow related. You flow over a certain amount of air through the mas and you hit fuel cut.

You nailed it. I can't even remember how many times I've answered that question.

For that, you get a rep point.

To clarify a tad, there are mitigating factors besides raw airflow numbers that the MAF sees that determine the exact point of fuel cut, including IAT, and some others I can't recall.

 

[1gFWD_90laser]

fuel cut has nothing on me. stock maf on 1g and i hit 21 22 psi on pump gas and no fuel cut.. all i did was remove all the honey comb things in the maf and cut the holes bigger and poof.. no more fuelcut.. down side for me.. crappy idle but i dont care becuse i was boosting 19 20 21 22 psi on stock 14b and no problems IM me if you need help

 

[unior]

fuel cut has nothing on me. stock maf on 1g and i hit 21 22 psi on pump gas and no fuel cut.. all i did was remove all the honey comb things in the maf and cut the holes bigger and poof.. no more fuelcut.. down side for me.. crappy idle but i dont care becuse i was boosting 19 20 21 22 psi on stock 14b and no problems IM me if you need help

you'll still hit it down the road again

but hacking the maf is a nice way to suppress it - i wouldnt go farther than removing the upper honeycomb though

also 2g suck with hacked mafs so that plan does not help 2gs

 

[DSM GREENHORN]

I have a B16G turbo w/ a Hallman Pro B.C. I turned the boost up, but immediatly hit fuel cut off. I kept hitting it all the way down to 11psi on my OBX Boost Gauge. Can't I run more boost? I don't have any ecu upgrade, but have a Greddy S-AFC and give it plenty of fuel. I also have an egt and it's always at or below 1. Don't stock GST's run 12-16psi? Why can't I run at least stock boost with a bigger turbo? What do I need to do?

 

[dave99gst]

1, fuel cut is mis-diagnosed as much as crankwalk.
2, afc does not = plenty of fuel if ya have stock injectors and f/p
3, you get 1 on the EGT ? ( i dont know what that means)

your prob is prob spark related, wrong gap dirty plugs or bad wires.
does your car stumble/shudder/miss ? thats not fuel cut.
fuel cut feels like you just hit a brick wall.

 

[steve]

Dave, You left out the #1 misunderstanding about fuel cut.

It caused by the ECU seeing too much airflow.
Positive corrections an SAFC will bring it on sooner.
Any air leaks post MAF will bring it on sooner.

Steve

 

[96tsiaddict]

2 ideas. boost leak (big one)
or possibly like in my case. The boost gauge has a break in the line and you are really running 23 psi. (on an almost stock 2g)

(HMMMM no wonder my car was so freaking fast till I hit fuel cut)

 

[Hammer_Gaidin]

2 ideas. boost leak (big one)
or possibly like in my case. The boost gauge has a break in the line and you are really running 23 psi. (on an almost stock 2g)

(HMMMM no wonder my car was so freaking fast till I hit fuel cut)

I so totally did that too. I was like..shit this t25 isn't bad.... I know better now.

 

[dsmjay]

i recently got my car back with a rebuilt 6 bolt motor swap. last night while driving it..it would start sputtering and missing around 3200 rpms...and it did this in every gear but first which actually would go alittle higher. so i would push in the clutch and rev the car while driving and the car would rev up fine so i threw out the whole rpm thing. so as it would get closer to 3k rpms i would take my foot outta the gas alittle bit and it would climb up past 3500 w/no problem. so i figure it has something to do with the boost. it does it around 4-5lbs of boost. i didnt wash inside the engine bay or anything just trying to figure this thing out. any help guys would be appreciated. most of the searching results just turn up ppl who hose down their motors.

 

[oldman]

You're right, definitely do a boost leak test. http://www.vfaq.com/mods/ICtester.html

 

[blackGSX2g]

My 6-bolt has been sputtering at light throttle around 2500-3000rpms with 0-vac/0-boost. Maybe its the same problem. Your not getting the random misfire CEL are you?

 

[dsmjay]

nope no cel. i think its probably just a boost leak thats what it really seems to be

 

[AHALLA05]

I cant figure out what is wrong wth my car.When i run the boost up to 12lbs in 1st thru 4th it just starts cutting out like i am hitting fuel cut?How could i be hitting fuel cut at 12lbs of boost.It will hold 12lbs if I do a pull from 5th gear but any other gear cuts out.Less than a month ago i could run 16lbs and be fine but ever since i resoldered my capacitors in my ecu it has did this. If i messed something up with that then my car probably wouldnt even run, right?I also just put in a new hallman boost controller. I have a 255 and i am venting(has ran fine befor with 16lbs)

 

[WhiteTsiAwd]

Have you tried doing a Boost leak test?

 

[AHALLA05]

yes, i tried it yesterday and didnt find any big leaks . my bov was leaking but not bad at all .Ill put back on my stock bov and intake and see if it works.Im wondering if it has something to do with my ecu but if i resoldered it wrong i dont think the car would run at allIm trying to get a log done but my tps will only go to 95.3%.What all should i log(tps, knock, rpm , o2...)thanks

 

[oldman]

yes, i tried it yesterday and didnt find any big leaks . my bov was leaking but not bad at all .Ill put back on my stock bov and intake and see if it works.

Either you have leaks or you don't. If you do, fix it. Are you venting as well? Boost leak is a very serious business, it can cause a lot of problems and is one of the most common cause of a early fuel cut. I would suggest revisiting the boost leak test until the system can hold 20 psi reasonably. Put back the stock bov and recirculate it until you get a maft.

Also make sure it's a fuel cut you're speaking of and not sputtering. When you hit fuel cut, it feels like hitting a wall, it will throw you around and make you go WTF . Good luck.

 

[sexycholo]

my 96 gst does the same. my sputters when it hits 12lbs. it used to go to 16lbs. but now it dosent. when any of my gears hit 12lbs it sputters and feels like fuel cut. It back fires constantly like shit, once it hits 12lbs. i went to many shops they dont know shit.
I have:
255 walbro
greddy 3" turbo back
upper intercooler p/p
greddy blowoff valve
greddy fmic
8.5 mag spark wires
new plugs
I just had new valves installed. timing,compression, is perfect. All clamps are tight and vacums are all in place. everything is tight. but then i went to my fuel pump and put stock back on. does the same thing. IM STUCK< DONT KNOW WHAT TO DO.

 

[oldman]

my 96 gst does the same. my sputters when it hits 12lbs. it used to go to 16lbs. but now it dosent. when any of my gears hit 12lbs it sputters and feels like fuel cut. It back fires constantly like shit, once it hits 12lbs. i went to many shops they dont know shit.
I have:
255 walbro
greddy 3" turbo back
upper intercooler p/p
greddy blowoff valve
greddy fmic
8.5 mag spark wires
new plugs
I just had new valves installed. timing,compression, is perfect. All clamps are tight and vacums are all in place. everything is tight. but then i went to my fuel pump and put stock back on. does the same thing. IM STUCK< DONT KNOW WHAT TO DO.

A REAL boost leak test is what you need to do, not a visual inspection. I would also suggest an afpr to control that 255. Good luck.

 

[psychlow]

I cant figure out what is wrong wth my car.When i run the boost up to 12lbs in 1st thru 4th it just starts cutting out like i am hitting fuel cut?

Sputtering/cutting out is not fuel cut, it's a combustion problem caused by air/fuel, ignition, or compression.

First step, fix your boost leak. If that doesn't fix it, check/replace plugs, wires, and/or your coilpack.

The boost leak will cause you to get richer and richer as you increase boost, because you're leaking more and more air. If you've got black smoke coming from the tailpipe when you're experiencing these problems, your boost leak is probably the culprit.

 

[AHALLA05]

Well i did another boost leak test and fixed my bov and all the other leaks and it still does it.It does not sputter like a normal boost leak would,it cuts out hard then runs for about a 1/4 of a sec then cuts out hard and repeats.I let off after the first or second time it cuts out .I am starting to think that it is my ecu but im not sure. I can hold it steady at 10lbs and it wont cut out untill some where around 5k rpms i know i should get a log but i havent had time.thanks for all the replys though.Im gonna go check my plugs and wires.