What is Fuel Cut

[Tanro]

What is fuel cut? I seen this term thrown around on the forums. But cant find any solid info on what it is. I did use search and did look at all the topics the forum suggested when I typed in my title.

So anyways what is fuel cut?

My car is stuttering at High Boost. I.E. whenever the stock boost meter (not gonna call that joke a gauge) hits the the third tick mark in 4th and 5th gear it buckles jumps stutters loose power for second or two etc. Then it picks back up. Sometimes it does it more than once.

Do I have fuel cut issues or something else?

 

[skatershawn]

No that's not fuel cut.. that's ill I will give you, there is a search engine on here. Please use it. Not trying to sound like a d*ck buy theres a whole thread that explains everything.

Goodluck.

 

[Indian]

Here is a thread I found helpful with fuel cut.

http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/186971-what-fuel-cut.html

You are not experiencing fuel cut. Check for boost leaks,check your ignition components, and spark plug gap.

 

[white92talontsi]

I have a question relating to Fuel Cut myself.
March 5th i am buying a 90 AWD TSI.
The car has a ported EVO III 16G and a VRS 3 Inch turbo back exhaust on it.
The guy states that at 6500RPM it Hits fuel cut. Ok but the problem is he says it does this at 7psi.

The car is stock other wise. I was assuming that in order to solve the problem the car needs a S-AFC. Am I correct?

 

[habitatguy187]

The Essential Primer on the Diamond-Star Engine Control Units - Chapter 7

 

[ricktb]

when the fuel actually cuts, how long does the take to resume fuel delivery? like a second or more? or can it blip on and off rapidly?

 

[MrBoxx]

Most people generally describe it as "hitting a brick wall."

Change your spark plugs to NGK BPR6ES, gapped to .028". Do a boost leak test. That is the most common cause of boost leaks. Reminder: To do a boost leak test, you NEED to have an aftermarket boost gauge installed. This is also the FIRST modification you have to make before making any other upgrade to your car that has anything to do with increasing power. That includes intakes, exhausts, boost controllers, blow off valves, etc. All of these will alter your boost output, and I can't stress how much you need to monitor that.

 

[Tanro]

I know about boosting cars. New to dsms though and have never expieranced a vac/boost leak that would the car hop and stutter like this. Why cant you people answer my question or a read what I post?

You can clearly see that I stated I used the search. Know what I typed in? "What Is Fuel Cut" then "Fuel Cut" and the Fuel+Cut and then What+Is+Fuel+Cut

Several threads mentioning it but none explain what it is.

 

[steve]

Several threads mentioning it but none explain what it is.

When the ECU measures airflow from the MAF in excess of what it thinks is normal it turns off the fuel injectors to protect the engine from a disconnected or burst vacuum line to the turbo wastegate that would otherwise lead to self destruction.

 

[Tanro]

Thank you. Thank you, I am recomending reputation for those of you that helped and didnt just say use the search.

 

[eclipse gsx]

fuel cut feels like you hit the brick wall at certain speed

 

[JEFFREYCASTGSX]

I have a question relating to Fuel Cut myself.
March 5th i am buying a 90 AWD TSI.
The car has a ported EVO III 16G and a VRS 3 Inch turbo back exhaust on it.
The guy states that at 6500RPM it Hits fuel cut. Ok but the problem is he says it does this at 7psi.

The car is stock other wise. I was assuming that in order to solve the problem the car needs a S-AFC. Am I correct?

It shouldnt be happening at 7psi. More than likely a boost leak, or spark issue such as plugs.

 

[PewPew90Laser]

While you're not hitting fuel cut, it sounds like you're not getting enough fuel.

Clogged filter, lazy pump or something that's just not grooving with fuel delivery. Also spark may play a part where ignition coils can have openings in the windings that only show when there's an abundance of resistance in the combustion chamber, like when it's pressurized before compression stroke.

 

[white92talontsi]

It shouldnt be happening at 7psi. More than likely a boost leak, or spark issue such as plugs.

I was thinking the same thing that it should not be happening either. I did a WOT 2nd gear pull but didnt carry it over 6k and it did fine.

My guess was that maybe since the Evo III 16g flows more than the 14b even on stock boost then maybe its possible that the MAF is seeing too much airflow even at 7PSI. Not sure.

 

[second_gen]

awww an answer youll like its might not seem correct but my car did the same stuff made me mad as H%ll but between me and my brother we figured it out, we ended up adjusting its ignition timeing and it stopped spit and sputtering yeah around 6500 RPM my car would lose power spit and sputter than around 7500 it would get all the power back but it was usless to me since i red lined at 8000 but try your ignition time reset it see if that works if not let me know

but to answer the question, fule cut is when your engine ask for a "X" amount of fuel and your fuel system cant supply it so you have fuel cutif you expierence that upgrade your fuel system such as injectors pump that should fix fuel cut

 

[haswesley]

When is the last time you changed spark plug wires? My car was doing the same thing. I changed plugs and plug wires, and that fixed the problem. Old plug wires allows the spark to terminate before reaching the plugs. It seems its a fuel problem, but its really a spark problem. Just a thought.

 

[Tanro]

Spark plug wires look like brand new B&W Select 7.5 MM wires. I pulled the plus out and cleaned them, sanded the crap of the electrodes and then gapped them to .28

 

[skatershawn]

Do a Boost leak test and make sure you check every line that goes to you intake.. i did one MANY MANY times and could never find my leak.. Friday i found it!! it was a seal on the brake booster!!
Letting out MASS Amount off air.. now my baby pulls hard and stays hard!!!

 

[Tanro]

I think It is my PCV valve leaking like a sonfabitch. I had cracked my old valve cover because I didn't realize that these VC bolts on dsms aren't supposed to be torque very hard. So I replaced it with my VC from the 6 bolt I plan on having rebuilt but I had to pull the PCV offa the broken Valve cover. It was sealed on there with some kind glue. I need to find something to seal it with.

I can feel air coming out from around it when the car is idling.

 

[PewPew90Laser]

I think It is my PCV valve leaking like a sonfabitch. I had cracked my old valve cover because I didn't realize that these VC bolts on dsms aren't supposed to be torque very hard. So I replaced it with my VC from the 6 bolt I plan on having rebuilt but I had to pull the PCV offa the broken Valve cover. It was sealed on there with some kind glue. I need to find something to seal it with.

I can feel air coming out from around it when the car is idling.

a junkyard valve cover will seal it!

or try 3m window weld

 

[Tanro]

I would have to buy an entire engine to get a valve cover from a junkyard here.

I had a spare though. And I know about 3m window weld. Gonna go pick some up. I have a couple of engine mounts that need to be fixed to.

 

[steve]

There's no need for window-weld on the rocker cover. If the PCV valve is leaking from the threads use some pipe dope. If it's leaking anywhere else it's either cracked or the gaskets are shot, just replace them and use RTV where shown in the FSM.

It will seal with the bolts at 3 ft lbs as long as the gasket hasn't turned into a rock.

 

[Tanro]

Gonna window weld the seal around the PCV or seal it with silicone.

 

[talontd2009]

I have a question about fuel cut that i just cant seem to find the answer. pardon me if this has already been answered, but i just cant seem to find it.
Anyway, ive been foolin with my boost controller to see how much boost my car can handle. I understand that running an engine too lean leads to problems.
My question is, will hitting fuel cut damage my motor? I would assume that an engine stopping so abbruptly would lead to problems, so tell me if im wrong before i turn my boost up anymore. im running stock internals and wanna know just how much pressure my motor can handle. thanks for your help

 

[MrBoxx]

Do you have a datalogger? Fuel modifications? Wideband O2?

Don't go turning the boost up on a stock turbo without a datalogger or some way to monitor your AF ratio, knock, timing, etc. Just because you don't hit fuel cut doesn't mean you aren't running super lean, getting pre-detonation, etc. You can have all that and still not fuel cut.

Without the supporting modifications and monitoring tools, you turn the boost up at your own risk. Then, you'll find out soon enough just how much pressure your engine took before it ate a piston.