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

 

[prophecy7115]

OK when i drive my car normal i have no problem, somtimes ill have crazy V-TEC, lets say i give it 75% Full throttle, from 0k - 3k the car fell allright like it should then after that its like BOOOMM! and then my eyes do this WTF .. it pulls like a raped ape, and other time it never hit that BOOM and pulls like a dead ape till redline, it feels like somthing holding back my motor, i would guess fuel cut, my timing retards?. I am running 15psi of boost, Intake filter (injen), Gutted cat, 2.75"catback, HKS ssq bov, Boost controller

 

[1993eclipseGS]

If you hit fuel cut, You would know it. It feels like running into a wall, Without seeing the wall. It is a VIOLENT jolt, It almost puts you through the windshield if you are not aware that it is going to happen.

You don't have an aftermarket exhaust, Or even a fuel pump... Correct? Why did you turn the boost up? Your car will only be slower when timing gets pulled. I would suggest doing supporting mods, Before raising the boost. No point in turning the boost up without at least a fuel pump and exhaust.

 

[prophecy7115]

Ok i read my whole life that the car can hold 16 psi with stock fuel, iam i right unless i have been reading wrong. Ok i already attemped putting it back down to 12 psi, and it still does the same thing so i left it at 15psi, What could it be? if its not fuel cut then its somthing holding me back. And yes i have a magnaflow.

 

[Defiant]

OK when i drive my car normal i have no problem, somtimes ill have crazy V-TEC,

What do you think this is?

 

[prophecy7115]

What do you think this is?

I think it was a joke, i really had no other word for the sudden jump in power over 3,500 rpm, sorry, But can anyone please help me out cause iam planning to upgrade the turbo and i hope that this wont happen to me. My car will run at full potential on one run and run completly different on the next.

 

[98autogstspyder]

I think you should provide us with a bit more information.

How many miles are on the car? When was the last time maintenance was done such as new spark plugs, wires, etc?

Look at your spark plugs that are in the car now and see if the electrodes are showing a lean condition? Do you know anyone with a 2g logger in the area? When did the car start hitting this "boom"? I assume you have a boost gauge right? Were any of the honeycombs removed? Provide us with every bit of information about the car that makes it not stock and we will do our best to help.

Also, you might want to get someone experienced and take them for a ride so that they can verify what this "boom" is. I assume it is fuel cut that you are talking about.

If it is not fuel cut you are experiencing it may be pulled timing. I know it is hot here in South Florida now, so it may be that your stock side mount intercooler is getting heat soaked. For now, turn the boost down to stock. Good luck.

 

[prophecy7115]

OK i am sorry, the boom is a sudden power gain on WOT, after 3,500rpm. Its like slow slow slow slow slow slow slow then out of no-were, its like a wooosh, and it always hasnt been like this, i know what the pull from the turbo spooling is like, this is different its like the engine is at WOT and then somthing is holding it back and then releases at 3,700k Then it pulls Like a . Then somtimes it will hesitate all the way to redline, like if whatever holds it back never lets go unless i suddenly let of and floor it again. BTW the motor is top shape well i hope, I just got some taylor wires, ngk plugs, the car has a religiously cycle on oil changes, it has 75,000 miles on it, but one wierd thing it that the guy who had the car before me put a perfect squared hole on the bov return tube back to the INTAKE pipe, he said it ran alot harder that it would lean out the motor, i was like , But when i cover that hole, i smoke out the back and run really SLOW!!!

 

[1993eclipseGS]

Get a new recirculation tube if yours has a hole in it, And recirculate your blow off valve. The previous owner is a dumbass. Check for boost leaks, And exhaust leaks before the o2 housing.

 

[prophecy7115]

Ok i put a new one in that i had, but the wierd thing is that the car runs like crap, i put the good tube on and the car is really slow, and smokes?? but it will only run like it should with the unmetered air coming in, And even then. ,

 

[1993eclipseGS]

What color is the smoke, And is your check engine light on?

 

[tstkl]

if you have a boost leak and your running your boost gauge off of the fuel pressure regluator line (like most people do, maybe ive got it wrong but its some line from the intake manifold to something to do with the fuel) then your turbo will actually be flowing at a much higher psi than what your gauge reads.... aka your maf will think that a lot more air is going into your engine and your ecu will turn off the fuel (fuel cut)... as for the sudden power at 3500 rpms, thats called turbo lag... most turbo cars have that problem.... and as for replacing the turbo, tell us which turbo your thinking about, and what fuel your thinking about running once you install your turbo,... (if you say stock i will have to slap you,....)

 

[ZUUHLSGSX]

Did this condtion all the sudden happen or did you change something in your set up? Unmetered air on my car is ALWAYS not a good thing.

 

[doug]

prophecy, did you take your car to the Miami DSM meet tonight? There's some very smart guys there that can help you diagnose your problem. If not, come out to the SoFla DSM meet next weekend and we'll have a look-see.

 

[Spoolin4Ever]

Please get a datalogger and log the car.

How long have you had it? How much maintenance has and has not been done?

What exact exhaust system is it? A stock exhaust with a magnaflow muffler?

Turn down the boost to 14 lbs.

 

[fatso]

I have a turbo smart fuel cut defender cranked to max to almost eliminate fuelcut and I hit fuel cut anything above 10 psi. Any one have a clue what the deal could be?

 

[spoolup]

Are you sure you are hitting fuel cut? Reason I ask, looing in your profile you have 550s and a SAFC which usually means you have leaned it out a bit, however being the SAFC actually controlles the amount of AIRFLOW seen to the ECU, rather than actually adjusting fuel. IE your ECU sees less air than your enigne is really take in thus the ECU delivers less fuel making you run leaner. But since your ECU is seeing this less airflow you are moving further away from the airflow it takes for the ECU to trigger fuelcut. Just out of curiosity are you logging your car with a pocketlooger or similar? What is the max timing you are seeing top of 3rd gear in a WOT pull?

More than likely the amount you have leaned it out has put you on to a lower airlow map which makes the ECU select a higher timing map. I had this problem with the SAFC when I had it. I was seeing 21* timing since I had it around -48 with my racegas settings and 110 octane (due to injector size and trying to maintain a descent O2. at 21* I would get detonation unless I ran a BPR7ES plug and changed them every 2000 miles). I would recommend pulling the plugs and looking at them, if questionable (even one) replace them all with NGK BPR6ES (about $9 for all 4 at NAPA) gap them correctly and see if the problem goes away? If so, the FCD is worthless to you. Personally i think they are worthless anyways since the override a "saftey" feature of the ECU and with proper tuning this condition will/ should not occur.

I also searched your name in the search box above and seen you made a post on SAFC tuning just a few days ago. Question. did this problem just start happening to you when tuning the SAFC? When was the last time you changed the plugs/ wires and with what type were they?

 

[fatso]

I am taking my car this weekend to Atlanta to have a good import shop dyno and tune my afc and the plugs I run are the same you suggested and it actually help push my fuel cut back installing the afc with the recommended starting settings for a similar setup, so its always been there. I think my prays will be answered with the guys in the dyno shop tuning it right so i get more than 50 miles every quarter tank(did I say running rich!) and my turbo up to its real potential. I will buy new wires tomarrow, what do you suggest?

much appreciated spool up

 

[prophecy7115]

OK i cant run the car with the covered bov tube, cause if i do i feel like the car is running 120 horses, and the smoke that comes out is white, so i tried to put the boost up to 15 its still slow then i tried 16 nothing then 18 and i figured why go further, i put the tube with the hole in it and turned the boost down to 12psi, and it runs pretty good. I couldn't make it to the Miami dsm meet i was working on my car all night. I did get my neighbor to lend me his logger, (he is a mechanic for Toyota), and my cel light is a pressure valve in the gas tank that might be malfunctioning, its stated that there is a pressure drop in my tank, thats all the cel light read, everything else is good, the weird thing is that the o2 sensor on the after the cat, is connected but the logger couldn't catch any reading from it, does it matter? the logger caught reading from the o2 senor on the o2 housing. The piping is mandrel bend 2.75" catback with magnaflow muffler. The Motor is in great condition, and the only major thing i did recently was seafoam the motor.? Thats about it. Well the car at 12psi ran allot harder than the car running at 14-18. Do you think my ecu got used to the unmetered air? which is very unlikely cause its unmetered, but? Well my car runs really good at 12psi, i am going to continue to see what my problem might be, I do plan on installing a 16g i am really looking for one right now. Hopfully i can find out whats wrong before i do that.

 

[spoolup]

I have heard mixed reports from all wires. I actaully went back to the stockers from MITSU. They seem to last for about ever. Magnacores have had problems arcing thru the boot, but work great until it happens (there are plenty of threads about that). Accell are nice and pretty cheap I ran those for about 2 years. Finally had one break when pulling them (they were pulled I swear, 100 times) so they were great, got mine from jegs I belive, cheap prices. Just avoid the autozone brand or factory mimics.

 

[crxp-o-s4now]

ok, ive searched through a ton of thread son here and have pretty much came up with the same options. When i recently bought my 1g dsm, it came with some to no vacuum lines attached. the car ran great but threw CEL'S and all that bologna..so that had to be fixed. Before inspection, me being a NOOB, had a local custom shop put my lines back on. I also replaced my computer because he said thats what needed to be done. yes i know the guy personally and he made no profit off of this sale so he wouldnt just f*&^ around with me. So once the vacuum lines are installed and new ecu is in, NO CEL'S!!YAY!! One bad problem!!! As im driving away from the shop, i give my car the ol' "show me some power" test and gun it to what i expected to be W.O.T! WRONG! as soon as i threw my foot to the floor, the car spiked at 17 psi (which i had normally at around 15/16) and once my foot was to the floor, the car seemed to pretty much stop. (meaning the turbo or something in the engine made a clicking noise as if the car wanted to move forward but couldnt) i have had no idea what this was and was hoping it was just the lines we installed back on the car. so once inspection is passed i have the lines removed..SAME SHIT HAPPENS ALL OVER AGAIN!! i go to gun it and it just pretty much stops! It seriously sucks not knowing what is wrong. so i turn the MBC down to around 15-16..it runs A TINY BIT better, however i can still feel the problem occuring. Could it be fuel cut or what? It doesnt feel like a HUGE JOLT but it feels as if when i floor the throttle, the car spools up, then stops, and you hear a clicking noise (if you keep on the gas)! I need to know what is wrong so i built my homemade leak tester and found a leak in my IC piping and resolved that problem..Now everything is all set..the boost controller is at 15 psi, the leaks are sealed, and IM STILL having this problem..someone PLEASE HELP ME! could it be the new computer?? or the wrong vacuum lines were removed?? i know for a fact that i have aroun d -20psi for vacuum at idle. Someone please help!! im sorry for wasting your time reading this but i cant seem to find out whats wrong and i cant continue modding untill this is fixed. basically if i floor the gas, i have NO POWER as soon as it hits 4,000 rpms!! SOMEONE HELPPPP!! im also available at larryd4233 is someone can chat online instead of through the forums!! thanks again folks!

 

[liquordrunk]

So when you hit 4grand does it feel like you hit a brick wall and it cuts back. Or does it keep on going up in RPMs. Have you upgraded anything, INJ, pump? Is your maf hacked? Cause if your car is completely stock you need to turn down the boost to around 13. cause your gettin fuel cut with stock everything at 17psi.

 

[crunchymilk]

I had a fuel injector not seated properly in the head and it was similar to what you're describing. I highly suggest a boost leak test!

 

[liquordrunk]

I had a fuel injector not seated properly in the head and it was similar to what you're describing. I highly suggest a boost leak test!

Good point.

 

[crxp-o-s4now]

did another boost leak test today and sounds like something from under the headers?? hope its not the turbo!! however, i believe this leak has been there since i bought the car because i RARELY gas the shit out of it. No it doesnt really feel like a brick wall, it keeps climbing however i let off and shift because the clicking noise continues and i dont like the feeling of someone ripping somehting out from my hood (which is what it sounds like). definately doesnt just stop but im not sure if ive experienced fuel cut or not. And about the 17 psi statement, when i bought the car it was topping off at around 15 psi and no more than that..now it hits 15 ish and hits that 4k range and somewhat stops!

also, what does it mean when a injector is not seated properly?

 

[hiimt0ny]

sounds like fuel cut. do you have any fuel management/upgrades.... if not you shouldnt put your boost past 15 or 16 psi..... or you will hit fuel cut, also check for boost leaks....