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

 

[dnhieu]

by the way the smoke is pure white in my eyes and i see the smoke a few times every day (very imbarassing). i know i got a small boost leak near the throttle body but i got the stock screws holding on the throttle body elbow so i cant get it tight enough to hold it down.

thanks

 

[oldman]

by the way the smoke is pure white in my eyes and i see the smoke a few times every day (very imbarassing). i know i got a small boost leak near the throttle body but i got the stock screws holding on the throttle body elbow so i cant get it tight enough to hold it down.

thanks

If you're sure it's pure white, I would do a compression test as well as checking the turbo. Now let's get back to the original poster you thread-jacker you.

 

[lloydslincoln]

Thank you guys, for all of the suggestions. I'm going to check the intercooler pipe along with the turbo tomorrow morning. I just took the car for a quick drive a few minutes ago and I hit about 7-8 PSI of boost without a problem, but I wasn't giving it much gas...I know as soon as it hits about 10 PSI or WOT it'll sputter and jerk like crazy.

Could the fuel pressure regulator really be the cause of the problems I'm experiencing though? With the jerking under high boost, the sputtering etc? Could the ECU be the problem? Being as the car has 450cc injectors in it (which was not stock for an automatic)?

Anyway, thanks for the help and I'll post my findings tomorrow.

 

[redmayns]

hey i just put in a greddy type s blow off valve, and for some reason every time i'm at WOT in second gear my car feels like i hit a brick wall for a second then just keeps on pulling, what is that and how do i fix it, at first i was venting but that i started recirculatring and it still does that same thing. help me out i have a 99 gst. and the piping is stock. let me know asap. and he i also have a new apexi boost control in box never used for sale avcr and i have an rfl bov for sale. lemme know if you guys want those. but yeah first the problem.

 

[4GSixty3]

If you're feeling like you hit a brick wall, that would be fuel cut. Fuel cut is computer-controlled so messing with your computer is the only way to not have it happen.

 

[fastezz]

it makes sense to me that you have boost leak, pressure cheak ur piping then getback to us.
Ryan

 

[4GSixty3]

If your car is stumbling under boost and NOT feeling like the way you described as hitting a brick wall, most likely you have a boost leak BUT that brick wall feeling is fuel cut, not a boost leak...

 

[zachakagoat]

Does this only happen in second gear? I would definately do a boost leak test but I would also check your spark plugs and make sure they are still in good condition and gapped correctly. When I bought my car the idiot didn't have them gapped right and my car would studder and feel like I was hitting something whenever it got to like 4500 rpms. :thumbdown

 

[fastezz]

Does this only happen in second gear? I would definately do a boost leak test but I would also check your spark plugs and make sure they are still in good condition and gapped correctly. When I bought my car the idiot didn't have them gapped right and my car would studder and feel like I was hitting something whenever it got to like 4500 rpms. :thumbdown

Yea mine did that too with fouled plugs. But yea also keep in mind you have a bad TPS too you will get fuel cut, my friends gsx when he first got it felt it was hitting a brick wall out of no where because his TPS was bad. But yea dude I am willing to put money in that you have boost leak, so check that out.
Ryan

 

[Quasimondo]

Did you replace the gasket at the BOV flange? If you're using the old gasket it's probably leaking from there and causing the boost leak.

 

[brianm96]

the EXACT same thing happened to me but it was in pretty much all gears, but obviously more noticable in the lower ones. you have to tighten the screw on the top w/an allen wrench way down almost to all the way tight.

 

[lloydslincoln]

Well.....I can't find a leak in the intercooler piping, and the turbo does not have any "shaft play" and seems to be OK. My problem is very, very similar to the problems 91orangeGST is having. I'm wondering if maybe it could be the plug wires or something? The wires are pretty new and the plugs are 2 weeks old, so I'm grasping at straws again....Anytime I give the car gas and hit a certain amount of boost (10 psi) it starts doing this...any other ideas? I'm running out! thanks!

 

[oldman]

Well.....I can't find a leak in the intercooler piping, and the turbo does not have any "shaft play" and seems to be OK. My problem is very, very similar to the problems 91orangeGST is having. I'm wondering if maybe it could be the plug wires or something? The wires are pretty new and the plugs are 2 weeks old, so I'm grasping at straws again....Anytime I give the car gas and hit a certain amount of boost (10 psi) it starts doing this...any other ideas? I'm running out! thanks!

1. Make sure that's a real boost leak test instead of a visual inspection.

2. When my turbo seal blew I had very little shaft play and it was boosting fine.

 

[freak4jesus_bt]

When both the 14b's on my talon and the laser went out, they both would white smoke when boosting and also letting off of the gas after boosting. The laser would also smoke when it sat long periods of time while idling. After the bearings went out on the 14b from the laser, it ate the turbines and so I bought a b16g turbo. Every since then, I've had NO smoking problems from my car.

Oh, it was white smoke, and it was because of the seals in the turbo going out. Good luck

And I'm running 14psi on a Big16g all day long on the stock fuel system, including the fuel pump, with no problems. 15psi is a different story. And when people say check for boost leaks, do it. It can solve alot of your problems. Later

 

[huafist]

Let's review the facts here:

1) Car runs like poopie.
2) Car billows white smoke.

Have you ran a compression check yet? Does the car overheat at all? Have you looked to see if your oil looks like chocolate milk or to see if there's oil in your coolant?

I'm betting it's a blown head gasket.

 

[Quasimondo]

Thank you guys, for all of the suggestions. I'm going to check the intercooler pipe along with the turbo tomorrow morning. I just took the car for a quick drive a few minutes ago and I hit about 7-8 PSI of boost without a problem, but I wasn't giving it much gas...I know as soon as it hits about 10 PSI or WOT it'll sputter and jerk like crazy.

Could the fuel pressure regulator really be the cause of the problems I'm experiencing though? With the jerking under high boost, the sputtering etc? Could the ECU be the problem? Being as the car has 450cc injectors in it (which was not stock for an automatic)?

Anyway, thanks for the help and I'll post my findings tomorrow.

No. Fuel cut is when your maf sees too much air coming in. This makes the ecu think that you're running dangerously high levels of boost or that it has a malfunctioning wastegate. The reason it thinks it see too much boost is because the turbo is working harder than it normally has to to maintain boost pressure that its losing from the leaks in your intake piping. While the outlet of the turbo is pushing 10 psi, the intake leaks are forcing the turbo to spool faster than normal and the maf is seeing the equivalent of ~20 psi or some other ridiculously high amount of boost. Go to the vfaq to see how to build a intake pressure tester and plug up your leak. Not all boost leaks will be clearly visible.

 

[wing91]

I have been trying to figure out my 2gb gst. I just got finished looking at the archives and found an article on fuel cut. I am curious my car has is all stock drivetrain except for a HKS filter cone on it. I have test everything or so I think with the exception of the Knock positioning sensor. My car is fouling out plugs but it is doing what the fuel cut article was talking about. It said that the car felt like the whole drivetrain was tearing out . Neways it sounds like it might be a ecu problem then and was wondering if my ecu out of my 2ga awd is the same so I could try swaping them. Also about the fouled plugs is that possible with fuel cut. Maybe the car is leaning out a higher rpms. The car doesn't idle surge but doesn't idle well at all.(around 300-500). Any help would be great. This problem started after the car had set for a while while I was living in Ohio playing hockey and it needed a new clutch. All started after changing the clutch and have been going crazy since. Thanks for any help

 

[Patter$on]

Got a 98 gst with evo III 16g, had a evo III ported o2 housing but last night i installed a dumptube. Drove it got on it a few times at the boost i had it set about before which was like 16, and it pulled hard i went to get tires and when leaving got next to an Evo and when i dropped to third and put my foot down it pulled hard but then made popping noises and stuttered. So i turned the controller down to 12 tried it again and it took a while then it creeped to 16 and got the popping and stuttering again. Now when i had the evo o2 on it i didnt notice any fuel cut when set at 16 i noticed when the gauge got to 16 it moved back and forth at 16 but couldnt feel any jerking or poping. All i could think of would be fuel cut but i would like to get that double checked with tuners. Also i though tthe dumptube decreased creep a great deal but i cant hold any pressure under 16.

 

[Patter$on]

ONe more thing sorry i also notice when under full accell, i can hear the dumptube and when i hit second and put my foot down i can hear the dumptube like the noise cuts in and out when under full boost.

 

[Patter$on]

i got on it today and i figured out what its doing,

the dumptube made my turbo creep really bad, my controller cant even touch it. i put my foot down in third looked at the gauge 19psi i saw that about shit myself and let off as im runnning stock injectors, so im suprised i thought dumptubes decreased boost creep i love the sound, but when i cant control the booost looks like its back to the evo o2 hosuing

 

[BMWHATR]

Looks like you solved the problem yourself

i got on it today and i figured out what its doing,

the dumptube made my turbo creep really bad, my controller cant even touch it. i put my foot down in third looked at the gauge 19psi i saw that about shit myself and let off as im runnning stock injectors, so im suprised i thought dumptubes decreased boost creep i love the sound, but when i cant control the booost looks like its back to the evo o2 hosuing

 

[oldman]

i got on it today and i figured out what its doing,

the dumptube made my turbo creep really bad, my controller cant even touch it. i put my foot down in third looked at the gauge 19psi i saw that about shit myself and let off as im runnning stock injectors, so im suprised i thought dumptubes decreased boost creep i love the sound, but when i cant control the booost looks like its back to the evo o2 hosuing

Creeping is a good performance sign. You're creeping because your 2.5" tubular o2 flows better than the evo3 o2. Instead of going backwards and solve the creep by getting rid of the added performance you should move forward and port the turbine inlet and wastegate path to accommedate the added flow.

 

[Patter$on]

the turbo is fully ported.
the evo o2 was also ported to match the turbo both from same company.
i dont think the wastegate is opening fully.

 

[oldman]

the turbo is fully ported.
the evo o2 was also ported to match the turbo both from same company.
i dont think the wastegate is opening fully.

That doesn't mean anything, my turbine and o2 housing was ported by Turbotrix and it creeped bad. There are two areas of special interest when porting to get rid of creep,

1. Take off material on top of the wastegate path so when you can actually see half of the wastegate when looking straight down. This way when the gate opens, air can flow directly out of the gate instead of making a almost 90 degree turn. The reason the dump tube didn't help you is because of this, without porting the entrance to the wastegate path you can still creep even with a external wastegate mounted on the o2.

2. Port behind the wastgate door to allow it to open so it's parallel to the flow, be careful with this step because you have a tubular o2 which is hard to port match what you did on the turbine side, port it just enough so the door opens more and clears the o2 side.

You can always go with external on the manifold but it costs more money and creats other undesireble side effects like noise and higher temperature in the engine bay...etc.

 

[andymoraitis]

As it turns out, I got the car on a lift and found a lovely boost leak on the lower IC piping. The fuel cut issue was solved with a Keydiver Stage III Eprom in a 95 ECU. Interestingly enough, my creep issues are also gone and with the MBC set to 16PSI, I get a spike to 17 PSI which settles back to 16 almost instantaneously.

Thanks for the help on the boost leaks.