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

 

[just_passed_you]

that doesn't make any sence. leaning out fuel = no fuel cut for me.
so I would assume the AFC is lying to the ECU saying there's not
as much air going through? Is that correct?

Right now, no fuel cut, stock injectors -15 all the way through the RPMS on Hi Throttle setting.

I assume the SAFC is lying to the ECU about air flow then.

 

[noreaga0221]

I assume the SAFC is lying to the ECU about air flow then.

Yes it does.

 

[steve]

I assume the SAFC is lying to the ECU about air flow then.

That's how the SAFC works. It intercepts the airflow signal and increases or decreases the signal when it sends it to the ECU. The ECU sees the new airflow and computes it's fuel needs from that. Since your using a negative correction the ECU sees less airflow and doesn't trigger fuel cut until you turn up the boost, raising the airflow and tripping over the trigger.

Steve

 

[VtecRex]

Tuning, Tuning, Tuning. I though my problem was a boost leak. WRONG. Take it up to a dyno and let the profesionally's deal with it.

 

[civickiller]

I am hitting fuel cut at 13psi bacouse i am running lean with current mods i have. What can i do to get rid of fuel cut? Fuel pressure regulator?

 

[beat90tsi]

Do a search, you are not hitting fuel cut because you are lean. You are hitting it because the ECU cuts fuel when airflow exceeds a certain amount, check for boost leaks before you do anything else.

 

[am00re34]

if you think you are running lean a regulator won't really do much. It would be better to upgrade your fuel pump to a 255 or a 190lph pump from walbro for example. As for fuel cut that is a different story. There are a few things you can do to trick your ecu into not cutting the fuel and you should be able to find those throughout this site.

 

[marcmsj]

first time i hit fuel cut, i thought my car blew up :thumbdown scary thing...

 

[golovemd]

Not sure if I should post or not. It seems like posting from newbies here is frowned upon. Anyway, I had problems that showed similar symptoms. Does your check engine light (CEL) come on when the problem occurs? If so then reading the code with a analog volt meter (if you don't have the more expensive tools required to get the code) should point you in the right direction. In my case, I was getting an error code for a bad TPS (throttle position sensor). After changing the old TPS with a new one, the car stopped having the problem and no longer felt like I was hitting fuel cut off at approx. 3000-4000 rpms. Just a thought as I see no one asked if you were getting any CEL's.

 

[Eastwood95]

Hey I was running 15-16psi on my 14b with the stock intercooler. I just installed an apexi GT FMIC and I started hitting fuel cut around 14-15psi. I noticed that my o2 volts dropped also at WOT to around .89-.91(before i tuned it back up). I wanted to know if this is normal.......I was under the impression that I could run the same boost when I installed the FMIC. Any opinions? experience with this?

 

[Rick4g63]

With a fmic, yu will get a cooler denser charge. A 255 lph fuel pump, 550cc injectors and a S-AFC can eliminate fuel cut.

 

[VtecRex]

With a fmic, yu will get a cooler denser charge. A 255 lph fuel pump, 550cc injectors and a S-AFC can eliminate fuel cut.

As long as you get it tuned the correctly. A datalogger would help with that.

 

[lloydslincoln]

Hello,

Hopefully someone can give me some answers..having quite a few problems with my 93 Laser AWD that I just bought (my first DSM). Seems to drive fine around town if I baby it. As soon as I give it gas though, or as soon as the turbo comes even close to 10psi, it begins to jerk violently and sputter, backfire, etc. Was pushing 15 psi boost. Freaked me out. So I came on here, read some posts, and turned the boost down to stock levels. Took it back out for a drive, and at first it seemed better...now it's doing it again, even at stock levels, although it doesnt seem QUITE as bad. It doesn't seem to matter what gear the car is in (it's an automatic). I attempted to start driving in 1st gear and that was even worse. Could barely move without it jerking around. I have to baby the car and try to keep it from boosting in order to drive. (seems to be OK around 7 PSI or so... can hear the turbo and all...but at 10, it will start jerking).

Now I notice while idling the car is smoking a little (white smoke)....wondering if this could have anything to do with the fact that the car does not have a cat (2.5" turbo-back exhaust, no cat/emissions removed)... or could it be something a little more serious?

It's confusing me...any help that someone could give would be appreciated..I've looked through posts on here but I'm not sure if I'm having the same problem as most of the people having "fuel cut". By the way, I'm running w/new spark plugs, wires, walbro 255 pump, boost controller & guage, 14b turbocharger (ported) & 450cc injectors, 2.5" turbo back exhaust. Thanks!

 

[FireyIce01]

Hello,

Hopefully someone can give me some answers..having quite a few problems with my 93 Laser AWD that I just bought (my first DSM). Seems to drive fine around town if I baby it. As soon as I give it gas though, or as soon as the turbo comes even close to 10psi, it begins to jerk violently and sputter, backfire, etc. Was pushing 15 psi boost. Freaked me out. So I came on here, read some posts, and turned the boost down to stock levels. Took it back out for a drive, and at first it seemed better...now it's doing it again, even at stock levels, although it doesnt seem QUITE as bad. It doesn't seem to matter what gear the car is in (it's an automatic). I attempted to start driving in 1st gear and that was even worse. Could barely move without it jerking around. I have to baby the car and try to keep it from boosting in order to drive. (seems to be OK around 7 PSI or so... can hear the turbo and all...but at 10, it will start jerking).

Now I notice while idling the car is smoking a little (white smoke)....wondering if this could have anything to do with the fact that the car does not have a cat (2.5" turbo-back exhaust, no cat/emissions removed)... or could it be something a little more serious?

It's confusing me...any help that someone could give would be appreciated..I've looked through posts on here but I'm not sure if I'm having the same problem as most of the people having "fuel cut". By the way, I'm running w/new spark plugs, wires, walbro 255 pump, boost controller & guage, 14b turbocharger (ported) & 450cc injectors, 2.5" turbo back exhaust. Thanks!

Do you have a fuel pressure regulator to go with that walboro?

 

[Eastwood95]

Well, i do have an SAFC but no fuel mods yet(stupid me) because i was running rich still at 16psi on the 14b. So I guess i can only run like 12-13psi on the FMIC/14b setup until I get pump&injectors............that sux

 

[Ian M]

The fuel cut isnt occuring because the air is cooler or denser after the IC. Fuel cut is determined by airflow (air mass) through the MAS. Colder ambient temperatures tend to bring on fuel cut quicker,however.


Fuel cut is occuring sooner because the airflow has been improved,and more air is being pulled through the MAS. The airflow limit has been met,and the ECU is putting a stop to the fun...

 

[Eastwood95]

is there any way to correct this(or trick the maf) without a fuel pump or injectors so I can run normal boost(14-15psi) or do I need to deal with it until i can get those? My MAF has not been hacked at all and I do have an SAFC..................

 

[Eastwood95]

well, obviously white smoke means OIL burning somwhere..........is your turbo whining?
Is your oil level straight? Leaking oil anywhere? Have you taken the intake off and checked the shaftplay of the turbo? Check the plugs again also........to start anyways

 

[lloydslincoln]

Turbo is not making any sort of "whine", it will hold boost and seems great until I hit around 10 PSI then it's like hitting a wall. Oil level seems fine, not leaking oil anywhere that I know of. I will check the intake/shaftplay of the turbo, and also the plugs, although I don't think those are the problem. I'm completely stumped! Oh...I think the FPR is aftermarket but I'm not entirely sure...even so, would that be the cause the type of problems I'm describing? thanks

 

[Eastwood95]

well i guess the next logical things to check would be the FPR, pump and fuel filter, thats one crappy problem you have there...................I guess white smoke wouldnt be a boost leak, but just to make sure, check your couplings to all of your intake/intercooler piping. Normally its black smoke when your leaking boost, but the stuttering symptoms happen when you have a leak somewhere...........and that would make sense...........i'm tryin to help, i just havent heard of this problem yet, let us know man...........

 

[oldman]

1. A boost leak is most likely your main problem, add to that the lack of afpr to control your 255, your car is running pig rich.

2. White smoke means burnning coolant but unburned oil can be really close to white as well. Check to see if the intercooler piping has oil in it. The turbo seal could be dumping unburnt oil and coolant on the exhuast side.

Compression test would be next if the white smoke persists.

 

[dnhieu]

i dont want to steal the thread but....im having the same problem also. i cant go into boost for long peroids of time or i will blow smoke like crazy. today i was swaping my gm sensor and i found a pretty good amount of oil in the piping. next i took my intake off to find a little in the intake and found a little around the inside of the turbo. does this mean my turbo is bad? i would be really pissted because i just payed someone 400 dollars for the big 16g. any help would be great

thanks
david

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[oldman]

i dont want to steal the thread but....im having the same problem also. i cant go into boost for long peroids of time or i will blow smoke like crazy. today i was swaping my gm sensor and i found a pretty good amount of oil in the piping. next i took my intake off to find a little in the intake and found a little around the inside of the turbo. does this mean my turbo is bad? i would be really pissted because i just payed someone 400 dollars for the big 16g. any help would be great

thanks
david

eclipse talon laser

Is it whitish blue smoke only under boost? If so, sorry to tell you but the turbo seal is probably toast.

 

[91orangeGST]

Im sorry but white smoke is NOT OIL!!! it is coolant!

Oil= blue
Coolant= white
gas= black


1 Thing that could be wrong with your car is your intercooler pipe is leaking. It used to happen to me ALL the time until I got new cupplings and clamps. When you are boosting at 15 it puts alot of pressure and it is easy to get a leak on old cupplings.

When mine was leaking it would jerk real hard when I would accelerate but when I would get up to 65 or so I could keep it from jerking if I didnt give it any gas.

 

[dnhieu]

its white smoke and i have no power at all. the car will begin to pull then it hits some kind of fuel cut and smokes like crazy. i drive around town with about 1/3 throttle puttin along everywhere. :thumbdown i was "thinking" it was a blown head gasket or something but u guys seem to think its the turbo. this would suck because i have been ripped off 3 times on turbos that were "supposed to be good".

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