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

 

[seth98es]

What psi boost are you running? WIth a stock turbo, the stock fuel system wont be able to run much past 15psi I believe. Stock fuel system + upgraded turbo = bad. Only thing you can do for now is to rewire the fuel pump, which may help a little. Otherwise, get some bigger injectors and a walbro 190!

 

[talongod]

no not in a parking lot only driving and right turns and yes my clutch is fine

 

[TC Mueller]

when driving my dsm hard around 4000-4500 it feels like it backfires. you get jolted forward and then it passes and everything is ok. i was driving my friend who has an sti and it did that and he said that his sti does it and its fuel cut. hes saying that my maf cant read the air coming in fast enouph and so it cuts fuel. but im not completly sure if thats correct but if so, could a 2g maf solve this problem? and if its not fuel cut then what could it be?

 

[JayRolla]

Yes its most likely fuel cut. Yes a 2g maf will fix this. Good for about 400-450whp. The 3g maf or evo maf is good for up to 650whp. Flows within 3% of a gm maf and easier to tune because it keeps the temp sensor. You will need fuel control to put the maf in. The maf will cause you to run a little lean or rich I dont remember.

P.S. If your hitting fuel cut you are most likely running to much boost without any fuel mods. I looked at your profile and you have no fuel control. I would turn your boost down unless you used a logger and your not knocking. You are wearing down the motor.

 

[vintagemuscle]

sounds like fuel cut to me.
if you are hitting fuel cut i would suggest performing a boost leak test first as a boost leak will cause you to fuel cut.

 

[vintagemuscle]

Yes its most likely fuel cut. Yes a 2g maf will fix this. Good for about 400-450whp. The 3g maf or evo maf is good for up to 650whp. Flows within 3% of a gm maf and easier to tune because it keeps the temp sensor. You will need fuel control to put the maf in. The maf will cause you to run a little lean or rich I dont remember.

P.S. If your hitting fuel cut you are most likely running to much boost without any fuel mods. I looked at your profile and you have no fuel control. I would turn your boost down unless you used a logger and your not knocking. You are wearing down the motor.

how much fuel he has or whether or not he is running lean or rich has nothing to do with "fuel cut".
fuel cut happens when you exceed the airflow cap that the mas can read. fuel cut is a safety feature so you don't melt pistons if for instance the wastegate line pops off and you overboost.

 

[TC Mueller]

well i have a 255 fuel pump but in one of my last threads someone told me i am over running my stock fpr. all stock injectors and whatnot though. so i dont know. right now im boosting around 17psi.

 

[JayRolla]

how much fuel he has or whether or not he is running lean or rich has nothing to do with "fuel cut".
fuel cut happens when you exceed the airflow cap that the mas can read. fuel cut is a safety feature so you don't melt pistons if for instance the wastegate line pops off and you overboost.

Yes you are right. I worded it wrong. I was saying if he droped in the 2g maf he will need fuel control. Hes running to much boost that is why he is fuel cutting. At 17psi you will be knocking like crazy. I would turn the boost down to 10-12psi if you dont have a logger. I had 24 counts of knock at 13psi on my 16g.

 

[TC Mueller]

it sounds like its running smooth to me.

 

[oldman]

how much fuel he has or whether or not he is running lean or rich has nothing to do with "fuel cut".
fuel cut happens when you exceed the airflow cap that the mas can read. fuel cut is a safety feature so you don't melt pistons if for instance the wastegate line pops off and you overboost.

Almost correct. The fuel cut value is preprogramed into the ecu and has nothing to do with overruning the MAF either.

TC Mueller, these are my suggestions, some were already given in the other thread but you don't seem to want to follow any but I will give it another try.

1. You need an AFPR for the 255.

2. You need to turn the boost down to about 14-15psi until you're able to log.

3. If memory serves, you're venting your BOV and it needs to be recirculated. If you're not venting, my appoligies.

4. You need to check the conditions and gaps of your plugs and wires.

5. You need to perform a boost leak test.

 

[TC Mueller]

all this takes money, money i dont have. i turned my boost down to 12, just oredred new plugs and wires so ill check the gaps when they arrive. as for the fuel pressure regulator that should be coming with my next paycheck. but can i perform a boost leak test myself? or do i have to take it somewhere?

 

[oldman]

Boost leak test.

 

[Quasimondo]

I'm ordering a logger this weekend, any suggestions on what to get?

Also is there anything I can do in the meantime to keep from flying back and forth in the seat every time I hit full boost?

Get the following items from eBay:

1. Palm m100 or m500 PDA (m100 has a black & white screen, m500 is a color screen)
2. Serial data cable for the palm if it is not included with the one you buy.
3. Datalogging cable to plug into the diagnostic port next to the fusebox.

Download a copy of MMCD. The latest copy is ver 1.8G, and a series of links for the program is available here

You can check eBay for this stuff, or search the classifieds for somebody who is parting out their DSM and has the entire logging setup for sale.

To keep from rocking back in your seat, I would suggest you don't go WOT until you have this problem taken care of.

 

[Nanan]

Stop playing around with the maft, return it to stock 450 setting and perform a boost leak test.

x2

Did you port that EvoIII? If not then you sir messed up. The EvoIII will boost creep like no other turbo I have ever seen unless you port about 2lb of metal out of the exhaust housing. Even ported to hell the EvoIII still loves to creep to 18psi for most when shooting for 15psi. I ported the everloving hell out of my turbo and I can not get it to hold less then 13psi, it always creeps to 18ish from about 5500rpm and up.

Also make sure your mbc or ebc, what ever you are using to control the turbo is actually hooked up correctly. Yea I may sound a bit daft but I have seen it several times on the locals cars when they had creep issues.

 

[talontsi9095]

Ok guys the other day i was driving my car about 25 miles to my house well my alt. light, battery light, and my brake light where flashing it did this for about 20 miles and when i was about 5 miles from the house almost all my gauges stoped workin well my car didnt start acting up till then. the problem with hitting a fuel cut that i have got alot worse!! when i had to make a turn to get on my road my car wouldnt go it was like it was trying to die on me then it just quit. well i was thinkin alternater but today i wetn and got my car my battery had full power and it cranked right up when i got home with it i toke off the postive cable and the car was still running so could it be my ecu???? Im sorry im not trying to hijack the thread but i figured if its my ecu it would fix my other problems.?

 

[TC Mueller]

thank you.

 

[oldman]

You're welcome.

 

[patty AT forge]

Do you have bad motormounts?
Check your harness for shorts (especially at the CAS, ecu, and the fuel pump), make sure your fuel line isnt getting kinked.

 

[talongod]

actually i think i do have bad motormounts

 

[rocknsnoboarder]

Turn your boost down! By repeatedly hitting fuel cut your putting a huge strain on your engine.

I'm only running the stock 9 psi. I do have a MBC connected, but I have not turned the boost up at all. I want to make sure the car is tuned right before I start increasing my boost.

Did you port that EvoIII? If not then you sir messed up. The EvoIII will boost creep like no other turbo I have ever seen unless you port about 2lb of metal out of the exhaust housing. Even ported to hell the EvoIII still loves to creep to 18psi for most when shooting for 15psi. I ported the everloving hell out of my turbo and I can not get it to hold less then 13psi, it always creeps to 18ish from about 5500rpm and up.

My turbo isn't ported. I've only had the car for a few months but I have never experienced boost creep or boost spike from the upgraded turbo. It always spools right up to 9 psi and just sits there, doesn't even budge.

Stop playing around with the maft, return it to stock 450 setting and perform a boost leak test.

I read the tech article about using the boostpro.net leak tester. I think I'm going to order one of their testers to test for boost leak on my car. After I read the tech article I was still a little confused as to how to do this. I understand that the tester gets hooked up to the turbo inlet, but does anything else get hooked up to the inlet or is it just this one connection and then start the car?
thanks for all the help. I really appreciate it.

 

[lilpastrana]

eclipse just installed new motor. engine runs fine sounds great when i try to acelerate fast cuts like a HUGE jerk. not a boost leak jerk like car shuts off jerk i think. What could be makin this do this. its only when it has boost and on the mbc if i turn it up it does it faster. what could be makin this hop ?

 

[chrisfrye]

have you tried turning the mbc down? haha

 

[lilpastrana]

yes does the same thing

 

[boostdog]

what psi are u boosting to? do u have a hacked maf?

 

[lilpastrana]

highest is 10 psi and not hacked