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

 

[twack]

is it set to karman

 

[JayRolla]

Whats it feel like when it hits fuel cut? Maybe its a missfire?

 

[JayRolla]

Over running the stock FPR with the 255 cant be helping the problem. Does it idle fine, have a missfire?

 

[iceman21221]

feels just like a rev limiter. car wont climb any higher in rpms and it just backfires with no power. If i dont floor it so the turbo only spools to 10 psi - using the gas as a boost controller- then it wont hit fuel cut but im only at like 40 % throttle. As soon as i floor it BAM it starts hitting fuel cut again.

 

[95blackGsTurbo]

What do you have your plugs gapped too. If I remember correctly, and I'm sure oldman will correct me on this, you aren't gonna hit fuelcut til around 2400hz. Check your plugs and see what they look like and are gapped at.

 

[iceman21221]

im having the same problem with my scm61/my car. except mine happens at 4k to 5k. ive tested it 8 times this weekend, changed the plugs and wires and still no luck.

 

[JayRolla]

Its true you wont hit fuel cut untill 2400hz except that not only does the ecu look at HZ, it also looks at how dense the air is. I would hit fuel cut in my 1g only when it got really cold out.

 

[oldman]

Well i think everyone is overlooking how major of a problem it is.

It is not a boost leak, no boost leak would be this severe, we've Boost leak tested it and it has a few small ones but this is something greater. The car WILL NOT rev past 3500, it just hits a wall and will make the car explode before you will get it to rev past 3500.

No one is suggesting that a boost leak itself can prevent you from going above 3k, however large enough leaks will trigger fuel cut stopping you at 3k. Post a log so we can see what's going on, there are alot of possible issues at hand that needs to be verified and resolved, for example,

1. Are you using all 90' wiring and sensors?

2. Boost leaks.

3. Fuel pressure.

4. compression tested.

........etc.....etc.

You're assuming the problem is caused by one thing when in reality, it can be combination of many.

 

[iceman21221]

plugs are gaped to .29 just changed them last night with brand new msd plug wires 8.5mm

 

[iceman21221]

since i installed the setup on friday its been no more then 40f degrees out. mabey thats my problem. its like 65f out today mabey ill check it out today and see how it turns out. i just cant think of anything else to do.

 

[MarkAngelo05]

Hey,

Figure it out yet?? What is your settings like on the AFC? with my 650's at 15psi, it took about -35 to get it to finally smooth out through 4k and 5k rpms. and that's still yielding me a .97 voltage on the stock o2.

Does your wideband go crazy through those rpms?? if so, then you are running PIG RICH, I was set at -28 accross the board, and man.. whenever I hit around 4k and 5k it was pretty much like hitting fuel cut, but its really misfiring due to being too rich. I remember hitting fuel cut with my 14B when it spiked to around 17 or 19 psi on a stock fuel system, it was litterally like hitting a brick wall! I could not keep my foot on the gas at all it was so rough.

I'm only running an EVO9/MR pump, so you're flowin way more with your 255 depending on your fuel pressure. Also, check your spark gap too, make sure it's .028 if you are boosting more than 15psi.
That is pretty weird because fuel cut should have been raised around 30% higher due to the negative corrections on the AFC.
Hope this helps.
Good luck man.

Mark

 

[iceman21221]

Well its fixed. I know one thing im NEVER buying another set of MSD PLUG WIRES. I must have got one from a bad batch. I swaped the MSD's for my old Magnacore wires and the problem is solved. im gonna say that JayRolla and you guys were right. Thanks for the help.

 

[oldman]

I checked for boost leaks and i couldnt find one leak. i tested the system to 30 psi.

As much as I have been around boost leak testing, I have yet to see one holding 30psi without leaks. Did you actually see 30psi on your boost gauge or did you set the compressor reguator to 30psi?

 

[iceman21221]

try swaping out the wires. i just solved my problem by putting my old ones back on. the brand new MSD's were bad.

 

[1990talon]

I blew a hole in my intercooler and it wouldn't rev past 2000 RPMs and yours revs to 3500 and you say it couldn't be a boost leak? I have all the T bolt clamps and silicone couplers too I still had a boost leak. just try the test before you say you don't have any just because you have all that stuff dosn't mean it can't fail and a boost leak bad enough could stop you from reving past 3500. Enough said do a boost leak the if that is not it we will help from there. Your asking for help well if you really want it you would listen to the people trying to help you. DO A BOOST LEAK TEST PLEASE!


Good Luck,
Brandon

 

[1990talon]

Also have you checked the waste gate actuator to see if it is sticking. you could be overboosting and hitting fuel cut because the computer sees it is overboosting.

 

[eldiabloz13]

i think its something to do with your safc. If you unplug it then it will go away. Then you have other problems then. I will guarentee you will have backfiring and bad idle with out the safc in. But it should cure the fuel cut and not being able to rev past 3500

 

[1990talon]

Also how does it run on idle?

 

[eldiabloz13]

truthfully......horrible but i somehow fixed it on mine. At first it would idle rough and die if you didnt keep pumping the gas now and again. When you first started it up it would rev reallll high then warm up and die down to like the hundreds. Then when i somehow fixed it the car would do fine. I re-set the ecu once the SAFC was off i think that may have been it.

 

[iceman21221]

i use a air compressor and run it untill it goes to 30 psi then i take it off. i didnt wanna push it any higher because my boost gauge only goes to 30. but i have had it to 30 psi before and blew the tester right out the coupler.

 

[V62GST]

There is a Boost cut work like Fuel cut,
but i dont know if our cars have boost limiter build in

you can get rid of boost cut just like Fuel cut

http://www.nolimitmotorsport.com/greddy/electronics.html#bcc

Greddy make Boost Cut controller

 

[MrBoxx]

Your car is most likely experiencing fuel cut, which is what happens when the MAS sees too much airflow. This is most often caused by a boost leak.

Do a boost leak test.

Do NOT install a fuel cut defenser. And our cars don't use the ECU to control boost, so a "boost cut defenser" won't do much good at all.

What is fuel cut? FAQ

 

[v2ner]

Colder weather = easy boostin (faster spool, boost creep, spike). Which usually leads to fuel cut. Don't try to get rid of it though, it has a purpose. Seeing as you are in MN, temps should be turbo friendly...very friendly.

 

[wvturbo2]

Don't our cars run richer when the motors are cold?

 

[v2ner]

Don't our cars run richer when the motors are cold?

I don't know about that but they are programmed a tad rich from the factory.