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

 

[97_eclipse_gst]

The whole thing is i have new spark plugs and wires. I got a full tune up, checked everywhere for leaks and it still backfires. Only in higher rpms and when its at full throttle.

 

[paranoidTSi]

Fuel cut is guarenteed to violently throw you into the steering wheel.

 

[pinder91]

Fuel cut is guarenteed to violently throw you into the steering wheel.

Sure is, as well as your dummy lights flashing for a second.

 

[Eastern Brigade]

Fuel cut is kinda like hitting a brick wall with you car. You know it when you hit fuel cut. You get thown forward into the steering wheel.

 

[JDNSBR]

The whole thing is i have new spark plugs and wires. I got a full tune up, checked everywhere for leaks and it still backfires. Only in higher rpms and when its at full throttle.

Like Oldman said, check for boost leaks and make sure your plugs are gapped correctly. When you do the boost leak test I would use soapy water to make it easier to find the leaks. Try this and let us know what you find out.

 

[fourreGsixty3]

I dont know what the problem with this is exactly, because it has never happend to me...hopefully never. The other guys seem to know what they are talking about with this, but it isnt fuel-cut. Fuel cut is just like hitting the govner on trucks, but for boost. Ive hit fuel cut a few times and it throw's you forward and the boost guage drops all the way back down.
Well good luck with this one man. Post when you figure out the problem, with what it was.

 

[lostsurfer402]

try a new ecu in it i had same problem it would break up and backfire when i hot boost in my vr4 i changed my maf plus wires then ecu ran beutifly after that

 

[chriseclipse]

lately every time i floor my car in second gear the fuel or something would cause my motor to cut off and misfire at 5500rpm. i heard some where that cold weather sometimes causes this problems. is that what i might be experience. I'm just making sure nothing seriously wrong with my car.
thanks,
Chris

 

[alex99gst]

You are hitting fuel cut. It is a common problem once you begin modifying your car. I would start out by checking for any obvious boost leaks that you can see, then when you have time, build yourself a boost leak tester like found here: http://www.vfaq.com/mods/ICtester.html

Do a leak test first and see if your intercooler piping wil hold 20 psi for around 30 seconds. Most of the time fuel cut is caused by a boost leak somewhere, wether it be at the j-pipe, injector seals, throttle body gaskets, etc... To ensure that you can get the most performance and best gas mileage out of your car, you need to do a boost leak test.

 

[chriseclipse]

Thanks for the response, i will try that out to see if i have any boost leak.

 

[97_eclipse_gst]

The whole thing with that is when the car does backfires the boost jumps around 5 pound on my guage. This is really starting to tick me off i spent over a grand trying to fix this and its still happenening, and the track opens next week

 

[oldman]

I will say this one more time, BOOST LEAK TEST!!!! And no, your visual inspection will not do.

 

[92fasttalon]

I know mine is a 1g but a set of new wires was all it took for mine to stop. I had a set of accel thspt on the car then went with a smaller diameter ngk wire. The ngk wires took care of all my problems. Sounds weird but it DID work. also check plug gap!

 

[silver bullit]

check to see if the plugs are gapped right. right size plugs (heat insullation). ignition check wires for holes/cuts. see if the plugs need replace. mine did that it was a loose plug and damaged wires,and or and what oldman said boast leak test would help route the prob.

 

[slickndual87]

Mine did the same thing. Mine did it because I had a bad exhaust leak right where the turbo mounted to the exhaust, it created a build up of "clean" air, and didn't mix well with the already mixed air, then backfired.

 

[Newlogics]

One or more clamps are loose on your intake piping.
When you build enough pressure, rubber pipe expands and lets air past the flange.

Pressureize your intake to at least 15lbs, and you will see what's going on. Just don't try bicycle pump, use compressor or a CO2 cartrige.

 

[Maverick3169]

Hey guys, after swaping MHI Evo III 16G's I run into this problem:
After about 5500 rpm my car begins to get lean... it starts at about 12.2 at 5500, then by the time 6000+ hits, its 12.8-9's and hitting fuel cut in 2nd-4th gear.

No matter how much fuel I add or take away at these rpms, the a/f's stay the same. I ever added 10%, and took away 10% with absolutely no change. By the time i'm about to hit 13 a/f ratio, it hits fuel cut (in every gear but 1st).

Also, I noticed that I can't control my boost pressure now. It always spikes to 25psi, then settles back down to 22psi. No, I don't have my MBC hooked up backwards or anything.

Just before I swaped turbo's, I wasn't having this issue at all. Keep in mind that prior to 5500rpm I'm able to totally control A/F ratio's. Right now I have it at set between 10.9-11.2 to be safe.

Any idea's?

 

[FORMONTOYA]

How about boost leaks and/or exhaust leaks pre O2?

Jim

 

[Maverick3169]

I was about to do a boost leak check, and I don't have any exhaust leaks prior to the O2 housing.

I thought that having a boost leak would cause you to see very rich conditions?

Thanks for the fast reply.

 

[Maverick3169]

BTW- the car runs fine when I use less than 80% throttle. Good A/F's, no fuel cut, nothing.
Not sure if this is helpful or not, just figured I would mention it.

 

[philly3384]

550's 255lph pump, big 16g, ported 02/ manifold, fmic and SAfc. It will hold boost at 15psi but anything past 17 forget it it hits fuel cut right away. Found only a couple little leaks but nothing to serious when performing the boost leak test . The car was tuned at 21psi before the ported 02/manifold and fmic. How much of a difference wowuld that make and what could i do now so i can reach 21 again.

 

[philly3384]

I thought fuel cut happens when the ecu reads to much air. Now why is the biggest cause of fuel cut boost leaks. Wouldnt the ecu read less air then?

 

[Ultimatedsm]

Search it to be honest, theres soo many threads on it, its not even funny .

 

[95blackGsTurbo]

Because the ECU reads the air at the MAF sensor. All boost leaks occur after the MAF sensor so the computer is adding to much fuel because it thinks it is reading to much air. That is why you can get it as well when you adjust the fuel on your AFC to high.

 

[eclipsegsx1736]

The airflow that that the ECU reads is measured right after the intake, by the MAS (unless you have a GM-MAF translator) . When you have a boost leak, the turbo must work harder to keep the boost at the level you set it at with a MBC or solenoid, because it's leaking out. Imagine blowing up a balloon. Then imagine blowing up a balloon with a small hole in it. You might be able to blow it up, but it will take a lot more work. Same for a turbo. It's having to suck in more air to keep the boost where it's set, so more air goes thru the MAS, and if the airflow is too high you hit fuel cut.