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

 

[ddavisaf]

Don't forget to check your plugs and wires. If you're stumbling while accelerating under boost it is usually caused by a poor ignition system. The most common problem when dealing with a poor ignition system are the wrong spark plugs. Like I said earlier in the thread, if you're not running NGK BPR6ES plugs gapped at .028" you're not running the right plug.

Here is a link for a boost leak test. Even though your idle is at -20 vac it doesn't mean you don't have a leak. If you can hold 20 psi for 30 seconds or more during a boost leak test it means you don't have a leak.
Test from the lower intercooler pipe for tests up to the throttle body. When testing for leaks at the throttle body and intake manifold test at the throttle body elbow. And if you have a manual boost controller disconnect it and run the lines back to their stock locations. Otherwise your test will not be accurate.
http://www.vfaq.com/mods/ICtester.html
Post back with how long your car could hold 20 psi.

 

[92GSXBaltimore]

fuel cut feels like you hit a brick wall or something for like 1/100th of a second. Its fairly violent. sounds more like your plugs/wires are dying or your leaking boost.

 

[3134]

from what my father is telling me, he will try to accelerate and as his foot is on the gas he loses power.

 

[HyperGSX]

yea same rpms mainly, and in any gear

 

[VtecvrsTurbo]

i HAVE the same problem, tubro spools, no pull, i put a new fuel filter and pan full pull, then a week or two later, same problem, i then put a new fuel filter in and no help! did leak test and have small leak on tb seals. But how did the first fuel filter fix problem right?

 

[HyperGSX]

turns out it was the leak on top of the bov that was causing this. The problem is gone now

 

[tstkl]

fuel cut at low boost is almost always a boost leak....

 

[gsturboman]

i agree with tstkl on this one. 9-10 times itll be boost leak when boost is that low.

 

[oldman]

fuel cut at low boost is almost always a boost leak....

This is correct, I'm dissappointed that it took 14 posts for this to be said.

turns out it was the leak on top of the bov that was causing this. The problem is gone now

If you're hitting fuel cut at 11 psi, most likely you have more leaks than just the BOV. I strongly suggest that you run a boost leak test up to 20psi, fix all leaks so you don't run into the same problem at let's say 15psi.

 

[gsturboman]

^^^ thats funny old man. only 9 people said it was boost leak, i quess that is how much it takes to get the fact and point out these days. no more 1 post ends discussion thing anymore

 

[oldman]

^^^ thats funny old man. only 9 people said it was boost leak,

I went back and re-read the whole thread, besides the thread starter's brief mentioning of possible BOV leak, no one, except for you and tstkl had mentioned boost leaks. Show me the 9 people you're speaking of.

 

[HyperGSX]

exactly, no even suggested a boost leak...but whatever thanks for the help

 

[gsturboman]

it was a joke oldman. just playing around

 

[4rsfed]

Hey, I have a wierd problem with my car and I don't know if it is fuel cut or what could be the problem. When I punch it out WOT it will pull through first with no problems and in second gear it will go until ~4000rpm and cut out for a split second really hard. (Its like you pulled the E-brake or something). In third gear it does the same thing at ~3500 and ~4500 and at ~5000 rpm. It does it only for a split second and the higher gear I go in the more often it cuts out. It only happens when it is at full throttle. There is also some black smoke out the back when I go at full throttle.
This problem has me completely boggled and I would like to finally get it figured out. Thanks

 

[gsturboman]

how much boost are you running. do you have a boost gauge. you shouldnt get fuel cut until about 16 psi. thats when mine hits but i dont know what u have. let me know that and well talk k bro.

 

[hereitcomes]

check the fuel system, as it could be a regulator, or a pressure sender. the cutting out at WOT is a good sign because there is more fuel getting injected rather than at idle, or cruise. and the black smoke comming out the back is also a good sign. black smoke means lots of fuel (you are running rich). so that fuel that is escaping through your exhasust should be going into your motor at WOT. good luck man. dont forget respect points if ive helped you buddy!!

 

[4rsfed]

I don't have a boost gauge yet but I might have to pick one up to see what I'm running at. It is totally stock so I'm guessing thats about 12 or so isn't it? I haven't really done any mods to the engine so I don't know why it is cutting out. I will let you know how much boost I'm running when I get a gauge.
Thanks for the replies.

 

[gsturboman]

sounds like your running rich just like (heritcomes)said. also, what kind of spark plugs do u use.might want to get ngk plugs my friend. that could aslo help some. let me know something.

 

[DrDSMGSX]

Here are my questions:
1. Is my ECU fixable? I will include pictures.
2. Would this cause my problems?
Okay, so car ran great up until about 2 months ago when I started getting fuel cut for no apparent reason. I will list the diagnosis I have been through.
1. Checked for boost leaks=fixed injector o-ring
2. Replaced PCV Valve
3. Checked and replaced spark plugs, NGK one range colder and gapped properly
4. Checked wires. Replaced with MSD's
5. Check MAF sensor, I am using GM MAFT and it was working properly
6. Ran several pulls on MMcD Palm, with no conclusive data, proper voltage, no knock, but right around 4 to 5k rpm would get fuel cut for no reason. Tried adjusting fuel ratio to rich and lean, neither worked. I would hear a clicking everytime I had fuel cut but thought it was just the motor, then today I did a first gear pull to see if miraculously the problem fixed itself and when the fuel cut I noticed the sound seemed more from under the dash around the ECU. So I pulled the ECU and smelled it for the nasty fish smell. It was present and I noticed some leakage from the capacitors.

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[steve]

Right now it's repairable but if you wait much longer it might not be.
The capacitors have leaked. It's likely that the damage under the caps is more severe and rather than fuel cut your getting the ECU power cutting out.

Steve

 

[DrDSMGSX]

Thanks Steve. Was wondering though how exactly it feels when it does this? Does it make a small stutter while crusing at times? I am just hoping this is the root of all my evils and when I get it fixed I will be able to pull to 7k again. Well I cleaned off as much of the acid I could till I get the new capacitors, so wish me luck.


Dan

 

[turbotalon46825]

Was wondering though how exactly it feels when it does this?

someone described it perfectly to me, its like going in one direction and a 1 ton truck with a chain hooked to your rear bumper is going another.

 

[DrDSMGSX]

Yeah, you are referring to fuel cut, right? If you are, Steve said what I am getting is not fuel cut, well I guess it is similar since the ecu is essentially shutting off the fuel supply, its just not relative to airflow. Do you know if it would create very small stutter while cruising though?

Thanks,
Dan

 

[Mike Marnik]

just replacing the capacitors may not fix it you also have to get the damage the leaking caused fixed. steve fixes then and is very fast mine in on the way back from him right now i cant wait. i would pm him if i were you if he hasnt already pmed you.

 

[steve]

Do you know if it would create very small stutter while cruising though?

In the early stages it could. The symptoms of unstable power to the ECU are pretty much all over the map as far as what people report. Some people can't rev over some RPM and others have random missing or rough cruise, some people never notice a thing until the electrolyte eats through a critical circuit and the ECU stops working or the caps explode.

You really won't know if it's only the ECU until you get the ECU fixed and the problem is gone.

Steve