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

 

[robcatch]

How old are your wires? Check them to see if there are any small holes or wear marks. They could be arking.

 

[oldman]

Tell us about how you test for boost leaks, the final result of your leak test? More importantly, you have already been asked nicely, fill out your profile.

 

[keithscianna]

Well i had a crap load of boost leaks a while ago.. Couplers where blown, j pipe to the TB had a hole in it i had o get welded, injector O rings where leaking, TB was leaking, BISS was leaking. got it all fixed and it started doing this fuel cut thing... I did a boost leak test again and it holds 15 psi with no probs no leaks...

 

[oldman]

Holds 15psi for how long before bleeding down to 0? What are you using to pressurize the intake? If you're using a compressor, what is the regulator on the compressor set to.

The number one cause of fuel cut are boost leaks.

 

[keithscianna]

Well i got it done yeaterday at my shop. they are a DSM shop an dwork only with dsm and other turbo cars. I didnt have enough money to have them troubleshoot my car just to do the boost leak test. But they said it ws good. I have a SAFC but it is not hooked up yet so maybe that will help.

 

[oldman]

A thorough boost leak test takes days if not weeks unless one has all the parts/seals handy, no shop will do that unless you're paying them $500. If you didn't physically see them performing the test yourself, I would go ahead and perform one yourself. Why you ask? Because boost leaks accounts for at least 90% of fuel cut issues. Contrary to popular belief and what the term itself implies, fuel cut is a function of airflow, nothing to do with your fuel system nor your ability to deliver fuel.

 

[kenamond]

And fill out your profile .

Your idle vaccuum seems normal considering your altitude. I assume you plan on getting or already have a logger so you can tune your SAFC?

Also, since you plan to mod your car, make a boost leak tester so you know first hand what's going on. I recommend the one in the turbo tech section with the gauge on it (man, I'm lazy tonight...okay, I'll go get the link)...

http://www.dsmtuners.com/forums/showthread.php?t=201554

Whew...I feel better now .

 

[romeen]

And fill out your profile .

Your idle vaccuum seems normal considering your altitude. I assume you plan on getting or already have a logger so you can tune your SAFC?

Also, since you plan to mod your car, make a boost leak tester so you know first hand what's going on. I recommend the one in the turbo tech section with the gauge on it (man, I'm lazy tonight...okay, I'll go get the link)...

http://www.dsmtuners.com/forums/showthread.php?t=201554

Whew...I feel better now .

Redemption always eases the mind, Mack. You may sleep well tonight.

Seriously, that is the boost leak tester that I made and used. It only takes about a minute to put together (no exaggeration) and works very well. IMO the $9 for the guage was well worth it so that I don't have to run back and forth to the cabin of the car to check what my boost guage is doing.

The $17 total I spent for the parts has already paid for itself many times over. Just like regular oil changes are a must for longevity of the motor, staying on top of your boost leaks is vital for good performance and driveability. I don't mean to beat this point over the head but anyone who does regular boost leak tests understands how they have a way of popping up.

 

[keithscianna]

Ok i got another boost leak test done and its still not leaking, i also made one but i dont have a compressor so i have to get one. But there is no boost leak. I got my CEL light pulled and my o2 sensor is bad. Would this casue what is happening to my car? Also lately when the weather is warm out and i am driving around for a bit, My car starts to bog down alot. It will happenin every and start at like 4k. When the boost kicks in it is kinda like its being held back and then if i would it i will get a back fire. Also when this is going on my idle is really low and choppy and it stalls at almost every light.

 

[keithscianna]

Do you guys think that adjusting my AFPR can help? Right now the screw is out all the way and is touching the valve cover.

 

[luvmygst]

Do you have a fuel pressure gauge? What is it set at now?

 

[romeen]

1) If it is your front O2 sensor that is bad then yes it will cause your car to have poor performance and you will be running very rich with bad gas mileage. Do you have black smoke that smells of fuel out of the exhaust? If you rev it after you have let it idle for a little bit is there a puff of black smoke? Your profile indicates a 3" exhaust. If you are running w/out a cat it could also be your rear sensor causing the CEL, in which case it would not be the cause of your issues. You can use a voltmeter to test it. If you need a new one you can find good prices here:
http://www.densoproducts.com/product.asp?productCategoryID=2


2) Even though a leak test was done I would still repeat it yourself. If they did not spray soapy water on all connections then there could still be a leak. Investing in an air compressor/air tank will pay for itself in a short time. Here is a recent discussion on some options:
http://www.dsmtuners.com/forums/showthread.php?t=256795

I would start with these two things. Then if your still having problems let us know.

BTW, what did you set your base fuel pressure at and how did you do it?

 

[keithscianna]

I do have a cat, So i am guessing that its the front o2. I am getting black smoke out the back too. when it bogs down and i keep the gas down the backfire will have a cloud of black smoke behind it. Also they did spray soapy water and the whole 9 yards. I really don't have the money for a compressor right now.
But they guys at the shop where 100% positive that there is no boost leak. They work with only turbo cars (DSM Supra Nissan etc) I'm not to worried about that. I will get a compressor soon tho just for the future.

 

[romeen]

Then yeah, get that front O2 sensor replaced and hopefully that should take care of things. You might need to let some PB Blaster soak into the threads and warm up the engine and use a breaker bar to get it out. Before installing the new one I would recommend using high temp anti-seize on the threads to make future removal easier.

 

[keithscianna]

Ok i will do that ASAP...

 

[oldman]

You'll need an O2 sensor socket.

 

[keithscianna]

What about my AFPR? Should i adjust it?

 

[oldman]

What about my AFPR? Should i adjust it?

What is your fuel pressure?

 

[romeen]

DON'T change your base fuel pressure in an attempt to compensate for running rich from a failed O2 sensor. BFP should be 43 psi when you disconnect the vacuum hose from the FPR and plug the end of it.

 

[mephist0]

hey, can anyone help me with this I got some questions on some upgrades I gotta do to my car, curently, the car has 3 inch turbo back, 190 fuelpump, 550 pte injectors and dsm chip, and I am hitting fuel cut, I would like to know wich way to go you, know, you never stop learning about dsms hehe, so please anyone is welcome to gimme your suggestions, and thoughts, thanks my FELLOW BROTHERS & SISTAS! i got the mbc and boost gauge too

 

[95TalonOwner]

Turn the boost down till you don't hit fuel cut or get a logger and safc to do some tuning.

 

[93GSX4me]

I agree - I didnt see anything about a boost controller or gauge. Monitor your boost and keep it at appropriate levels . With that said , fuel cut can be addressed with "HKS Fuel Cut Defencer" ...

HKS Fuel Cut Defencer website page

 

[mephist0]

any more suggestions? advice? thanks

 

[spyderturbo007]

I would stay away from the FDC at all costs. Fuel cut is a safety measure that I highly suggest you don't bypass. What if your wastegate gets stuck and suddenly you are boosting 30psi and don't know it. At that point the ECU has no way to protect you if you are running a FDC.

Anyway, what boost are you running? Is your chip burned for the 550cc injectors? Do you have a logger? Have you done a leak test?

 

[mephist0]

I got the boost all the way down, and yeah the chip is programmed for the 550's and I haven't gotten a logger, is that a must? I want to get the dsmlink