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

 

[Kevin Klapwijk]

I had the same case only a few hours ago...but now it's fixed!

I have a small 16G, stock fuel pump and injectors. I hit fuel cut around 5500 RPM. I just finished installing my HKS BOV (venting) and my AFC and my fuel cut is gone now.

I thought i'd need the upgraded fuel pump and injectors to fix my premature fuel-cut problem but I guess all i needed was an Apexi S-AFC!

 

[GSntncT]

Do you have an Air/Fuel gauge? Are you running rich? Do you have an AFC? What kind of intake do you have? You need to put all these things into effect and figure out if it is something as simple as your air/fuel mixture and combustion.

-Alex

I would not be too concerened about what the A/F ratio says, as there is nothing you can really do with that to change what the ECU "sees". If you added these parts with out a logger, or an SAFC at the least, then you're just basically running through a mine field blindfolded. Get some sort of actual tuning device.

 

[ocdiddy02]

i have an apexi safc and a a/f gauge

 

[Chaddycakes21]

i have an apexi safc and a a/f gauge

You'll learn sooner or later on Dsmtuners that the a/f gauges are a joke. They arent accurate whatsoever. The only way to get a accurate read out from a a/f gauge is to buy a wideband such as the AEM Uego.

 

[undrboost]

i have about 1500 miles on my new fully built motor. .20 over CP Pistons, H-beam rods, Ferra 1mm oversized valves, walbro 255 , stock boost ect. ect mods in my profile. well today i was on the highway going 60 mph and i decided to see what this can do so i down shifted to 3rd gear 10lbs pulls all the way to redline shift 4th gear i get to 6200 bam fuel cut felt like hit a brick wall. slowed it down and took it easy back to my house. i was pissed
could i be out flowing my stock 450s? it was about 40 degrees out today if that makes a difference.

 

[Irrational]

i have about 1500 miles on my new fully built motor. .20 over CP Pistons, H-beam rods, Ferra 1mm oversized valves, walbro 255 , stock boost ect. ect mods in my profile. well today i was on the highway going 60 mph and i decided to see what this can do so i down shifted to 3rd gear 10lbs pulls all the way to redline shift 4th gear i get to 6200 bam fuel cut felt like hit a brick wall. slowed it down and took it easy back to my house. i was pissed
could i be out flowing my stock 450s? it was about 40 degrees out today if that makes a difference.

Get a logger if you dont have one and do a boost leek test

 

[CanadianTSi]

Boost Leak.

 

[kottyking]

Do you have a fpr for that wally 255? This out flows the stock fpr and if you go w/ a 255 you need the regulator.

 

[MrNobody]

i have about 1500 miles on my new fully built motor. .20 over CP Pistons, H-beam rods, Ferra 1mm oversized valves, walbro 255 , stock boost ect. ect mods in my profile. well today i was on the highway going 60 mph and i decided to see what this can do so i down shifted to 3rd gear 10lbs pulls all the way to redline shift 4th gear i get to 6200 bam fuel cut felt like hit a brick wall. slowed it down and took it easy back to my house. i was pissed
could i be out flowing my stock 450s? it was about 40 degrees out today if that makes a difference.

Perhaps the real question should be... why are you running stock injectors on a fully built motor? I am guessing that you are probably pulling enough air but not enough fuel. I would think that with an AFC and some 550s you would have no issues at all. Or perhaps 650 - 680cc. Also I might have missed it but are you running stock BOV? stock upper intake pipe? If you are I am suprised you didnt blow the BOV right out of the tube.

MrNobody

 

[MrNobody]

Do you have a fpr for that wally 255? This out flows the stock fpr and if you go w/ a 255 you need the regulator.

I dont think you need a FPR just yet but that wouldnt hurt either. Perhaps the next mod should come in a bundle. Injectors, Rail, FPR, of course if your a budget builder then do injectors first. The stock rail should flow enough until you start pushing 500+whp.

 

[dsm-power36]

check your plugs, are they gapped right, make sure the tips didnt melt away at all.

 

[Dragon TalonTsi]

I had that same problem, but with my setup, it's a bit differetnt. Do a boost leak test, that is a major problem that is often overlooked with a lot of tuning and rebuilding, check your plugs for being fouled or gapped incorrectly, all of your connections, hot and ground, fuses etc. check everything over from step one. I had a major leak in my TB and it caused so much problems, and it was just my TB elbow leaking, and it was insane at how much power I was losing. Double check everything, the smallest detail could be robbing you of all that power....

 

[vintagemuscle]

Perhaps the real question should be... why are you running stock injectors on a fully built motor? I am guessing that you are probably pulling enough air but not enough fuel. I would think that with an AFC and some 550s you would have no issues at all. Or perhaps 650 - 680cc. Also I might have missed it but are you running stock BOV? stock upper intake pipe? If you are I am suprised you didnt blow the BOV right out of the tube.

MrNobody

10psi with a s16g is fine with stock injectors. a s16g won't flow much more than a 14b at 10psi. do a boost leak check.

 

[undrboost]

no logger, no safc, stock fpr, stock injectors, stock boost, greddy bov type s. its crazy this thing pulls extremely well when its warm out side but when its real cool out it kind of sounds like its trying to pull timing. i am going to check for boost leak + other leaks tonight i will also check my ngk plugs out and get back. oh all my intercooler pipes have been replaced w/hard pipe up to my fmic. i kind of ran out of money after the build so im thinking of getting some injectors and safc next. but i am just not going to drive the car until i get those dropped in. thanks

 

[mattsdsm]

Ok I have a 1990 GSX I got it about a month ago. I t has a k&n filter and is supposed to have a 255 walbro fuel pump. The guy also made like a home made MBC, which is set at 16-17lbs. Well anyway the weather is starting to get nice so I did a couple of 3rd gear pulls. and when I got to about 4-5 grand the car would buck or jerk a couple of times so i would let off. Is this from fuel cut? If so would larger injectors help or what?

 

[paranoidTSi]

fuel cut isn't bucking, its a violent jerk and you'll be hitting the steering wheel VIOLENTLY when it occurs. Its almost like your car turns off in the middle of driving it. I'm not sure what the problem is but its not fuel cut from what you are describing.

 

[trd-2-dsm]

the car's knock sensor may be pulling your timing. or your plugs maybe fouled

 

[fourreGsixty3]

Thats not fuel cut for sure, Ive only hit it once and dont want to hit it again, haha, hit my head on visor bit of ceiling. Also fuel cut wouldnt really happen around 4-5k, mine happend at 6k. Not sure what your problem is...maybe it lies with in your fuel system, but I couldnt be sure.

 

[mr2turbo]

sometimes a bad tank of gas will cause that. It's happened to me before.

 

[stirpicult]

do a tune up. also, did he have a fpr added or not?

 

[remmargorp]

Fuel cut can happen at 4-5000 RPM.

I have never driven my car harder than 5,500 (5,500 max, 95% of the time I stay below 5000).

I have hit fuel cut approximately 6 times in my car. The first two times it was a hard jerk.

The third and fourth it wasn't as bad, fifth was bad and the last wasn't as bad.

Depending on where you live, the air density/temperature/humidity can effect when you hit fuel cut. (The bad times it was in sunny weather with temperatures below 30 and no humidity, the not so bad times it was at night, temperature 40-50, with low humidity)

Also note: the bad experiences happened in 3rd gear, the not-so bad happened in 4th.

 

[mattsdsm]

It just happend again today when I was messing around with some friends. This is happening like everytime I do I 3rd gear pull at WOT. Anyway how would I tell if it is or isnt fuel cut. Is there anything I can do to just rule it out or whatever. Oh someone asked if he had a FPR and the answer is no.

 

[Spooling99]

You might be overrunning the injectors with the 255 without a AFPR.
-ADAM-

 

[DSMark]

Trust me, you'll know when you get fuel cut for sure, it's kind of like hitting a brick wall. The one time i hit fuel cut i hit my head so hard on the steering wheel i thought i felt retarded for about 5 minutes.

 

[Spoolin_Racer]

If you were hitting fuel cut, then it would feel like the brakes suddenly went off in your car and your car quickly came to a hault. As some have said before, it feels like hitting a brick wall. I am sure you will know when fuel cuts hits you...Not a good feeling at all