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

 

[97GSX-509]

Hmm.....that would make sense....I think I have a warped throttle body. I did a boost leak test and I had mass air coming out of there. So, until I can afford a used 60mm TB, I just put 2 extra gaskets on each side of the TB (using gasket maker), and also used some high-temp silicone on the spot.

Yes, my Stage 3 KeyDiver was SUPOSSED to stop fuel cut (25%).....but was thinking that either A) I still had a boost leak, or B) I am heat-soaking the IC. Because sometimes when I havent been driving all night....I can pull through 1st,2nd,3rd with no fuel cut at all. And then later, after making a few pulls.....it begins cutting again.

I don't think that it is knock, because I also have the stock boost gauge converted to a Knock Sum Gauge.....and it doesnt ever jump.

 

[Boost95]

Ok, I cant figure my car out. It had alot of boost leaks but I fixed them all, rechecked and no leaks anywhere. Dont go by my profile I need to update it. The car is as follows:
92 TSI AWD 5 spd.
3" downpipe
3"VRS Exhaust
Upper I/C pipe with type S
SOme gauges

Thats all that should matter.

Heres what happens. The car will pull hard and once it hits 13psi and stays for a few seconds it will hit fuel cut. I should be able to get 15-16 just fine. IF anyone has had similar problems please post what you did to solve it. If your not sure what your talking about please dont post. Thank you in advance.
-MIke

 

[versatilx1]

http://www.dsmtuners.com/forums/showthread.php?t=186971

 

[Boost95]

Thanks for the reply but I am very familiar with fuel cut and what it is. This is my 5th DSM. I had the exact same mods on my 90 with no problems. I did a boost leak test again to make sure nothing came loose or fell off and everything is fine. No leaks at all. Other than a boost leak I cant think of anything to cause it to hit fuel cut. Anymore replys?
Thanks,
MIke

 

[oldman]

Thanks for the reply but I am very familiar with fuel cut and what it is. This is my 5th DSM. I had the exact same mods on my 90 with no problems. I did a boost leak test again to make sure nothing came loose or fell off and everything is fine. No leaks at all. Other than a boost leak I cant think of anything to cause it to hit fuel cut. Anymore replys?
Thanks,
MIke

Could also be a defective mas sending wrong signals to the ECU.

 

[Boost95]

Thats an idea. I will try it 2morrow since I have 4 or 5 sitting in the garage. If it was acting up wouldnt it still happen at low boost? Thanks for the helpful reply.
-MIke

 

[oldman]

Thats an idea. I will try it 2morrow since I have 4 or 5 sitting in the garage. If it was acting up wouldnt it still happen at low boost? Thanks for the helpful reply.
-MIke

Hard to say. Maybe it's off but not dead, doesn't hurt to try since you got bunch of them. Just double checking, how much psi was the system able to hold during the pressure test? I would also pull the ecu and inspect it really well. Good luck.

 

[Boost95]

Well, the test held enough pressure that it blew the cap off my boost leak tester before leaking out anywhere. I checked the ECU, It looked fine. Nothing smelt burnt and nothing was leaking as much as the eye can tell. Any other ideas other than swapping the MAF's. I want to get my other parts on that I have sitting around, but its worthless to add anything if the cars not running right

-MIke

 

[oldman]

Nothing smelt burnt and nothing was leaking as much as the eye can tell. Any other ideas other than swapping the MAF's.

A lot of people mistaken fuel starvation or bad case of bogging for fuel cut until they hit a real fuel cut one day, how sure are you?

 

[Boost95]

100% With only 13psi why would it be starved. Unless something is clogged or getting tired. I have a new pump for it but I dont want to put it in until I check all possibilities.
-Mike

 

[oldman]

Unless something is clogged or getting tired.

That's why I was asking, weak pump, clogged injectors, defective fpr or ignition related. The key is whether you truly hit fuel cut.

 

[Boost95]

Well, it would still be fuel cut correct? If something was clogged then it would not be feeding the engine enough fuel fast enough therfore it would hit fuel cut?

 

[oldman]

Well, it would still be fuel cut correct? If something was clogged then it would not be feeding the engine enough fuel fast enough therfore it would hit fuel cut?

That would be fuel starvation. The term "fuel cut" is specifically referring to ECU cutting off the firing of injectors when it receives maf reading exceeding what is allowed pre-programed into the ecu to guard against run away boost. Hence why boost leak, boost creep and out of control boost causes fuel cut.

 

[DSM BEEYACH]

Can you describe what exactly happens when you hit the fuel cut. Also are you able to red line while siting in neutral. Does it act the same hot or cold.

 

[Boost95]

10-4 , I will try to swap out the maf for another 2morrow. Then go from there. Thanks for the help 2nite!
-MIke

 

[Boost95]

Its like hitting a brick wall, no power at all. Im sure I can redline in nuetral although I never tried it. Do you have something informative to add?
Thanks

 

[oldman]

Can you describe what exactly happens when you hit the fuel cut. Also are you able to red line while siting in neutral. Does it act the same hot or cold.

Feels like your car was chained to a pole and you just ran out of chain.

 

[Boost95]

Feels like your car was chained to a pole and you just ran out of chain.

EXACTLY

 

[DSM BEEYACH]

Its like hitting a brick wall, no power at all. Im sure I can redline in nuetral although I never tried it. Do you have something informative to add?
Thanks

Yes i know what it is and what its like. Iam just trying to find out if you have a fuel cut or if your having fuel starvation. Just see if you can red line while siting in neutral. also does your car idle just as before this problem or not.

 

[steve]

Just see if you can red line while siting in neutral.

That's just stupid and a quick way to ruin an engine. Never redline an engine with no load on it.

Steve

 

[DSM BEEYACH]

That's just stupid and a quick way to ruin an engine. Never redline an engine with no load on it.

Steve

You won't ruin an engine by redlining it for a few seconds and, iam only talking 7500 rpm's or so just to see what happens. If it redlines slowly with out stumbling but, has trouble geting there its fuel starvation. If you cant even redline it and it stumbs its a fuel cut.
Also do you hear a large discharge of air and still hear the turbo spin when it happens or no. There are diffrent fuel cuts one do to a leak, two can be do to more boost than fuel, three could be do to a bad MAF like mentioned. You can always put in a fuel cut defender just to see what happens.

 

[steve]

You won't ruin an engine by redlining it for a few seconds and, iam only talking 7500 rpm's or so just to see what happens. If it redlines slowly with out stumbling but, has trouble geting there its fuel starvation. If you cant even redline it and it stumbs its a fuel cut.
Also do you hear a large discharge of air and still hear the turbo spin when it happens or no. There are diffrent fuel cuts one do to a leak, two can be do to more boost than fuel, three could be do to a bad MAF like mentioned. You can always put in a fuel cut defender just to see what happens.

IMNSHO, your just digging yourself a deeper hole.

There is no way your going to generate the airflow without a load needed to trigger fuel cut. The engine won't typically even build boost without a load.

In DSM land there is only one fuel cut. That's when the airflow exceeds the trigger value and the ECU turns off the fuel. There are various reasons you might hit that trigger with boost leaks being the most common with lightly modified cars. The reason for the ECU having fuel cut code may be related to injector capacity but the more accepted thought is it's to protect against a problem with the boost control hoses and wastegate to keep the engine from overboosting if the hose happens to fall off.

I still think free reving the engine with no load is a really bad idea no matter how long it's for.

Steve

 

[Boost95]

IMNSHO, your just digging yourself a deeper hole.

Agreed, Thanks for trying tho.

Steve, Do you have anything I shoudl look into? Im going to go down in the garage and try another MAF and take it for a ride. I will post with the results in a few minutes.

Thanks,
MIke

 

[Boost95]

Im putting the MAF from my 90 GSX on that I know works. I have a question tho. I am doing a boost leak test once more. How much air is suppose to come from teh bleeder on the boost controller. I think there might be a bit to much air comign from the bleeder because I can hear it coming out pretty loud. I will get the maf back on and go for a ride.
-MIke

 

[Boost95]

I just took the MBC out to eliminate that problem. But something started leaking again When I put 15psi in it , its leaks out within a few seconds. The leak is comign from somewhere under around the fuel rail. I cant pin point it tho. Back to the garage I go.....