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

 

[Defiant]

You loosen an MBC to lower boost.

 

[oldman]

You loosen an MBC to lower boost.

Unless it's a bleeder type valve like TurbosXS.

 

[joobienooner]

Well i have my boost set as low as it goes and it doesnt phase it. And it doesnt really creep...i just jumps up. Could it be a faulty actuator, like the diaphram in the actuator could it be broken and just not seeing there is 18psi?

 

[oldman]

Well i have my boost set as low as it goes and it doesnt phase it. And it doesnt really creep...i just jumps up. Could it be a faulty actuator, like the diaphram in the actuator could it be broken and just not seeing there is 18psi?

Run a line directly from the compressor outlet to the wastegate.

Post back the result.

 

[joobienooner]

Alright ill have to do it that when i get off of work tomorrow. By putting on a 34mm flapper isnt it easier to blow open at higher boost...because i dont plan on keeping it where its at. I want to run about 20psi.

 

[oldman]

Alright ill have to do it that when i get off of work tomorrow. By putting on a 34mm flapper isnt it easier to blow open at higher boost...because i dont plan on keeping it where its at. I want to run about 20psi.

My 38mm holds 20psi just fine so your 34mm should hold up unless you're dealing with an old and tired (like me ) actuator.

 

[wvturbo2]

My turbo xs keeps my boost right around 15-16 psi all the way turned down. it doesn't creep it just goes straight up like you said. Could it just be the boost controller ?

 

[iceman21221]

So i just finished installing my new setup

• 
  PTE SCM 61
  Tial externally gated tubular o2 housing
  650's
  255 fuel pump
  new fuel filter
  aem ugeo wideband
  greddy front mount
  7ES plugs
  SAFC
  intake
  3 inch exhaust with no cats

I think thats about it. I checked for boost leaks and i couldnt find one leak. i tested the system to 30 psi.
I run the car off the wastegate spring which is 1 bar. I keep hitting fuel cut around 4k sometimes 5k rpm.
The wideband is reading perfect right up till the time it hits fuel cut. Any help guys.

 

[Deadly BlaZe]

uh...i don't get it?

EDIT: when i saw the post all it said was: asdfasdfas asdfasdf asdfsdad asdfadsf

 

[JayRolla]

Do you have it tuned, or just running that boost without one, but 1 bar is not much. How long does the pressure hold and how fast does it drop.

 

[95blackGsTurbo]

What does your wideband read before fuel cut. You really can't compensate for 650's with just an SAFC. Are you sure its fuel cut? What Hz are you reading when it breaks up?

 

[iceman21221]

im gonna take it for a ride now and see how many hz there is and check the wideband at fuel cut.

You really can't compensate for 650's with just an SAFC.

i ran the 650s with my t28 and they tuned just fine with no problems at all. i took all this stuff off of my buddies car and right back on my car. his car ran perfect at 18 lbs with no issues. my car also was running perfect right before the switch.

 

[iceman21221]

alright guys its around 10.8 to 11.3 for the wideband and the hz are at 1104 when it hits fuel cut in third gear. when i make a pull in 2nd gear the hz read 1210. I hope this makes any sense. also i think my first o2 senser might be goin bad. hopefully it doesnt have anything to do with the fuel cut. no check engine light tho.

 

[spoold]

So we just got my friends vr4 converted 90 galant GSX running, and it runs great minus one HUGe problem:

Under any throttle, at 3k the car just hits a wall. It shakes and stutters and feels like its smacking a wall. When you let off its obvious its building boost, but its like the boost isnt going past the pipes.

Its got a 255/560 injectors, afc1, 14b running wastegate (no boost gauge). I began to think fuel cut, but at any settings on the afc it does the same thing, zeroed out, -15%, -22%, -27%. It acts the same way! settings on dsmlink are 2 cyl upward throttle, its running a 90 ecu and wiring harness.

I know the question sounds dumb but i cannot figure out what it could be?

 

[iceman21221]

Have you tried boost leak testing the car yet.
I dont know much on the dsmlink so i cant help you there. try the leak test and let us know what you come up with.

 

[spoold]

No dsmlink on this car, and its way more than any boost leak could cause, and its got a full hardpipe/fmic with t bolts and sillicone couplers so it doesnt have any massive boost leaks (throttlebody is rebuilt and injectors have new seals). It wont even let you get past 3k it shakes/stutters so badly. You can kinda get past 3k in first but its obviously not good for the car to do.

 

[iceman21221]

I began to think fuel cut, but at any settings on the afc it does the same thing, zeroed out, -15%, -22%, -27%. It acts the same way! settings on dsmlink are 2 cyl upward throttle, its running a 90 ecu and wiring harness.

You said the setting for dsmlink are 2 cyl upward throttle, do you mean SAFC. if so the SAFC should be set a 4 cyl upward throttle.

 

[spoold]

When its set on 4cyl the revs are way too high on the safc (it reads like 5k when youre at like 2200k)

And yes i meant safc sorry :0

 

[iceman21221]

i dont know man, im stumped now. other then a boost leak i dont know what to say. sorry.

 

[FlatBlackTerror]

i dont know man, im stumped now. other then a boost leak i dont know what to say. sorry.

are you using the stock maf or a vr4 maf? Id say try replacing that and see if it helps

 

[elfroggo]

Do a real boost leak test and see what you find. Even if you think it's all good it may not be. It's better to do a real boost leak check then going around replacing things.

I went out and bought a compressor to do boost leak test

 

[spoold]

ok so it IS set on 4 cyl, we changed out the maf with a real vr4 1g maf, same thing, then we tried a vr4 ecu that was out of a running vr4 and same thing.

So...

maf changed and ecu cahnged.. still doing it

 

[iceman21221]

It dont take much for a boost/vac line to get hard - crack, then when under boost blow apart. i have had it happen to me a enough.

 

[Rex2342]

This may sound dumb but did you check to make sure the IC and IC pipes aren't plugged or blocked off? My friends Honda did something similar to this and it was because he left the tape on the intercooler inlets. Ruined a $500 turbo too.

The only other things I can think of are maybe the ECU wiring is off. Did you use a complete harness from a 90 eclipse inside and under the hood? I don't know a lot about Galants though so maybe someone else could help you out there. What about the fuel pressure? Are you using the stock FPR? You should really get a boost gauge and do a leak test too. Can you use logger on a Galant like you can a TEL? If so get one hooked and check the MAF signal to see what it's reading.

 

[spoold]

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.