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

 

[My91TalonTSi]

My 91 TSi has a full 3" turbo back exhaust, 2.5"o2 housing with dump, Dejon intake, and a Greddy Profec II.

At 5,000 RPM's under WOT I am getting fuel cut.

I have boost set to around 15-16psi with no spikes or creep.

It has been a while since I have modded a T/E/L but I did not get fuel cut this early on with my last car, a FWD 2g.

With my old car the correction was a well tuned AFC. With that being said, I have probably answered my own question on how to fix the problem, but is there anything else that I can do. I'm not sure if the fuel pump rewire would help a situation like this.

Thanks for the help.

 

[midnght]

Yes, it is an injector thing. Get bigger ones and a device to tune it with. THe difference in this 14b and the old t25 you have is flow. The 14b flows more than the t25. Enough to make a difference at lower psi.

I understnd what you say about the 2G not getting fuel cut this early. I ran 19psi on my t25 and NEVER hit fuel cut. I don't recommend anyone do this. It was a personnal decision to run that much. If I attempted that with the stock injectors on a 14b (19psi) I would be gettting fuel cut just as you are.


With the addition of injectors, pump, and a controller you can get that car into the 12's. Providing you have the exhaust upgraded already.

 

[JoeWagon]

I don't think its been clear enough of an answer. You will always have fuel cut without a modified ECU. The way to get around it is to make the ECU see less air. An S-AFCII compensates for larger injectors by reducing how much airflow the ECU 'sees'. Coincidence?

1g's have larger turbos... so of course they are going to hit fuel cut (lbs/rpm) sooner at the same boost.

Lastly, I ran 21psi on my T25, I wish people would stop telling others to avoid higher boost like the plague.

 

[My91TalonTSi]

Well, these are exactly the posts I needed...thanks.

It's amazing that the 14b is that much more powerful then the old t25 i use to have in my 2g.

And I also ran my 2g at about 19psi with creep to about 22

I guess for now I will lower the boost a little bit to avoid cut.

Thanks again.

 

[PhoenixRPR]

My stock 1992 Eclipse GSX seems to be having a fuel delivery problem. This intermittent problem occurs during acceleration. It can occur in any gear. It feels like fuel cut (sudden jerk). It is not "studder". I've had a studder problem before and know the difference in feeling. I fixed that by replacing ignition coil packs, ignition wires, and spark plugs. This definitely feels fuel related. Weird thing is that I can go an entire day of driving w/o the problem showing up, then the next day it can show up 10 times. From what I can tell, it is not temperature related either. Also, its important to note that I am also getting an intermittent code 41 (injector circuit) being thrown. (no cel)
However, I had the car hooked up to one of those very expensive Snap-On diagnostics machines and we verified that all the injectors are working perfectly, which coincides with the findings I had from my personal datalogging results. We also pulled the fuel tank and examined all the baffles, and there were no blockages. The fuel pump is also working properly. I would love to here some great feedback, thanks.

 

[Judacoth]

sounds like a tough problem with no easy answers. I understand you checked all your grounds and they were OK. You could have 1 broken wire that make intermittent contact and shuts off your injection system. You could have a bad computer. Does your car idle up when you turn on the A/C. Did you replace the caps in the computer. did you know that just the little bit of heat you applied to the board to replace the caps, even when using a heat sync, could adversely affect other components on the computers board. Did you know that a bad or defective Air Flow Sensor could give you the same results.

 

[RACER-X]

I would go with the ecu 1st make sure all your plugs are making contact if not it would make your car react like you were fuel cutting. you should also check the wires in the harness to see if there in good condition. After checking if your still having the same problem you may want to see if you can borrow a friends ecu and plug it into your car, if you do and problem stops then you know its your ecu.

 

[PhoenixRPR]

Ok I need to modify my first post. The description I posted was based on a 3rd person perspective. Now that I have my car back and have driven it around, here's what I have experienced. On a full tank of gas, the car drove 45 miles without a single problem. Once I hit 45 miles, the car (once it has reached temperature) exhibits a severe loss of power, a studdering/jerking back and forth as I accelerate, not one sudden fuel cut jerk. However, this is not your normal dsm-studder problem. I've already reworked the ignition system (plugs, wires, coils, etc), I still feel this is fuel related. Also, its important to note that once this problem occurred, the car threw a check-engine-light at me (Code 41). As I said before though, the injectors have been tested and work properly.

 

[slow_talon]

hey you guys i'm posting a new thread to ask if somebod has had the problem i'm having right now and how did you fix it. i have a 2g eagle talon tsi fwd auto and i installed a 14b and a walbro 190lph fuel pump but now the problem is that i want to boost the 14b and it can't even get to 20psi without hitting fuel cut and now that it is hitting fuel cut the engine doesn't want to pass 3500 its like bugging out. help me out you guys. thanks

 

[Rick4g63]

I would suggest

- 550 cc injectors

- Apexi S-AFC

These WILL eliminate fuel cut.

 

[92awdgsx]

well with a 14b and 450cc injectors you will hit feul cut at 20 psi.

 

[Generation1JeY]

whats apexi S-AFC?

 

[Spellmen]

It is a piggy back fuel tuning device. It modifies the airflow that your ECU sees so that you can add or remove fuel. 20 psi is a little much on the 14b, you will probably see more power at 18 psi or so. At 20 you will get heatsoaked on the stock sidemount pretty quick and will probably get some knock.

 

[Rick4g63]

Spellman is correct. go to the site below and read about it:
http://www.roadraceengineering.com/newafc.htm

You will need a fuel management system. hks, greddy, an others make a FMS.

20 psi is a lot for a 14b I would keep it at 16 psi max.

 

[Twizzle]

20psi is fine for a 14b, any higher and its not doing anything beneficial....

of course..turn the boost down for daily driving, but i shouldnt have had to tell you that.

 

[DevilSperm]

I would suggest checking for boost leaks before spending an as load of money on tuning stuff.. http://vfaq.com/mods/ICtester.html

 

[Coup D E'Tat]

20psi is fine for a 14b, any higher and its not doing anything beneficial....

of course..turn the boost down for daily driving, but i shouldnt have had to tell you that.

I keep hearing this, and still don't understand why anyone would turn down the boost for "daily driving." You aren't hitting 20PSI every time you step on the gas to go down the street, so why turn it down? 20PSI is fine for daily drivers.

/semi-hijack

 

[THE_ARTIST_]

You need to RESET the ECU because it will "remember" what caused fuel cut and do it again.

Take off both battery terminals for 5 minutes or so.

Good luck

gsxtacy

Bastard....took the words right outta my mouth. i hit fuel cut and i had to reset the ECU and it runs fine now , id turn the boos down a little too, until you got somthing to tune it with.

 

[slow_talon]

i just installed a walbro 190lph fuel pump on my 2g talon fwd auto and i'm running a 14b turbo and i was trying to run 17psi on the fuel pump but i seem to get fuel cut and i had to step down to 15 psi. So i was thinking of buying a fue pressure regulator but i don't know if that would help a bit. if it does how much pressure should i put or how can i tune it. please help asap

 

[Tarantula]

Base fuel pressure on a 2G is 43.6 psi with no vacuum.

 

[blcknspo0ln]

as far as I know, you shouldn't be able to run 17 psi without some sort of adverse effect. I run 16 psi on a 190 and my b16g and it's ok.. anything past that it'll cut out

 

[UK-DSMer]

You are going to need fuel control AFC etc. and larger injectors to increase your tuning bandwidth. Fooling the ECU in to seeing less air will allow you to run more boost as the ECU thinks its further away from a dangerous situation. In your current case, seeing far to much air flow though the MAF / MAFT.

 

[slow_talon]

would a fuel pressure regulator work?

 

[UK-DSMer]

No, that wont help at all. You see your ECU is watching the airflow through the MAF and is not happy with the amount of air you're trying to shuv though there.

You need to show the ECU and different airflow. The most common way is larger fuel injectors and a SAFC. You can then lean out the larger injectors by reducing the Karman signal from the MAF.

If you don't understand what I'm typing about I suggest you read of on ECU fuel control, Open and Closed loop etc. Once you understand how the system works that knowledge will turn in to power. Make the investment and read.

Right now, turn your boost down to about 14 - 15 psi. This will bring the airflow down and the ECU will be happy. If you want to make more power, you're going to have to spend more $.

 

[PhoenixRPR]

Well, from what I have read about vapor lock, it is temperature related. As the exhaust heats up near the fuel lines and then the car is shut off, the fuel left inside the fuel line vaporizes. Then the next time the car is turned on, while still warm, the metered amount of air coming in is mixed together with vaporized fuel causing difficult starts. Once the car cools, starting no longer becomes a problem. However, I do not believe these symptoms coincide with my car's problem. I have left the car cold for 2 days. I am going to run some more tests on it to see if I can narrow down variables.