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

 

[MattnGsx]

any ideas? any ideas at all?

Check your plugs to see what they look like. Maybe change your plugs and your wires. I had this problem after a couple of months when I first bought my car. I had a bad plug and wire. Hopefully thats all it is.

-Matt

 

[GORBS88]

I have the same problem....is not a slipping clutch but somtimes you step on it and as he says.....the exhaust gets way louder and deep and the boost is where it is suposed to be but theres no power.....then you shift and bam,,goes like crazy....only happens once in awhile....it has always did it but since i got 2.5dp and 3inch back it has got worse....and sometimes it will pop out the exhaust aswell.....anyone know what this could be....i am car smart i am a licensed mechanic but am new to the dsm world......my car...92 tsi awd...mods, hacked air can, k and n, 180 stat, 16psi, and full exhaust......pls help...

 

[kyle h.]

We'll I've asked this questions several times, each with more detail as I do more and more tests, but I havn't gotten any replies with ideas and I havn't been able to find the problem.

background info: 93 tsi, recieved with no tranny and some vacuum line mess.

ok, on to the problem.

it idles like a cammed v8. doesnt even sound anything like a 4 cylinder, the car and engine both rock back and forth, idle is between 700-900 rpms. other than that the car runs fine and fast. and i get a light fuel cut at 6k rpms, just fuel, no ignition cut from what i can tell.

low fuel trim: 93%
mid fuel trim: 85%
high fuel trim: 82%

O2 sensor is good from what i can tell, going to test and replaces next chance i get. mas/maf is good from what i can tell, resistance decreases as heat increases.

when the car is idling and i pull any one of the plug wires off, nothing changes. car continues to idle the same.

all plugs look the same. #4 wire resistance is a bit high, but i still get spark. when i pull #2 plug wire i can hear it arching back by the coil somewhere.

it sounds like i have a miss, but i cannot find anything that leads me to believe that i do have a miss.

fuel pressure is fine, injectors sound fine, fuel pump seems fine.

things that have been done to the car: 2.5 downpipe, and fuel pump rewire.

im planning on checking the egr next and then pressurizing the intake to check for vacuum leaks.


any ideas, comments, questons?

p.s. im about to give up on a normal idle.

 

[guitardave24]

Hope this is enough information...

I only have bolt-ons with an MBC set to nearly open (screw might fall out) and am able to hold 14 PSI generally all day long at WOT. However, I seem to be hitting fuel cut at low throttle in some cases. When I'm just cruising in 2nd or 3rd gear at 1/4-1/2 throttle and 6-8psi, the sound of rushing air comes in (as usual) at the passenger side and gets louder and louder until I shift. But sometimes, if I don't shift, and just let the RPMs rise while holding throttle, the air sound will get really loud and them BAM, it bucks hard (if at any time I go WOT, the rushing air stops and it pulls hard). I know what you're thinking.. boost leak. But, like I said, my gauge says I can hold at WOT and I never fuel cut up there. This may be a coincidence, but it also seems to happen more when I'm quite low on fuel.. but maybe not.

I've attempted to run a boost leak test. Was mostly unsuccessful due to air leaking through into the valve cover and out of the tailpipe... But I've checked, double-checked and triple-tightened all IC and intake pipes.

Couple things here..
WHy would I still get 14 psi w/ the Joe P MBC nearly all the way open? Could it be simply a bad PCV valve? Vacuum issue instead of air mass? Any ideas about the fuel cut at 1/2 throttle?

Any ideas would be greatly appreciated. I'm running new NGK 7 plugs w/ NGK wires. All mods in profile.

Thanks guys.

 

[MattnGsx]

Was mostly unsuccessful due to air leaking through into the valve cover and out of the tailpipe...

It shouldn't leak at all! How are you testing?

what are your plugs gapped at? What wires are you using?

-Matt

 

[guitardave24]

Gapped at 0.030 w/ DSM NGK wires... I tried capping off at the UICP/Throttle body, and it held the boost (I think), but of course, I was reluctant to do that because I can't get a boost gauge reading that way.

I built an intake leak tester as per the VFAQ, attached it to the turbo inlet and pumped air via an air tank.

 

[MattnGsx]

I built an intake leak tester as per the VFAQ, attached it to the turbo inlet and pumped air via an air tank.

If you can hear air coming from somewhere you have a leak. You shouldn't here any air leaking. Fill you compress up with air, shut it off and blast (w/ the vfaq method)air into lower icp through the intercooler. Make sure your compressors is off so you can here if there is an air leak.

At high enough psi, it will blow out the blowoff valve.
Let me know how this turns out.

It could be a vaccum leak look at the fuel presure regulator make sure the lines hooked up? Another thing is to check your blow off (are you dumping air or recyclingback to the intake?) see if its leaking there. Just run your car and put your hand in front of the valvue (pull off the snorkel to check).

-Matt

 

[awdsm drft]

You're going to have leaks. If you're hitting fuel cut at 14lbs you have leaks.

 

[Cooljock]

well have only driven my car for a day with my new turbo xs rfl but i haven't had my car do this yet again to me so im crossing my finger. it could have been the pipe leaking boost cause I took the pipe out and reput it back in so i dont know if it was leaking at the bov pipe or what. so we will give it a couple more days. i dotn get back from kscity until sat. i got to replace my alternater agin it my 3rd time sence christmas. now this one stop working when my car get hot after 30-40 min then it will just run off the battery wired my voltage regulator who know I know qick fix for it thou.

 

[talontsi01]

I know this topic has been discussed many times before, but I couldnt find an exact answer.

Can upgrading the stock fuel pump on my car to a walbro 190 get rid of fuel cut? Has anyone had some first hand experience by going this route.

 

[ZmanIV]

I recently purchased a 98 gst and am having the same type of problem.
The problem was not as noticible at first and after I dumped some fuel injector cleaner into the tank the problem started getting worse. I checked the plugs and saw the mix was lean.
I talked to my uncle and he suggested to replace my fuel filter. After that I had better luck and thought it was just crap in the fuel lines or tank that i dislodged and was cloging up the fuel system. someone else suggested keep on dumping injector cleaner into the fuel system until it runs clean.
unless I hear otherwise I will wait and get a new fuel pump, tank filter, main filter rewire the pump for more power and maybe do some research into the new fuel pump relay.
If anyone has any other thoughts or if im going in the wrong direction please let me know.

 

[-GSX-Falcon]

I have a 190 and no it will not help with fuel cut. Fuel cut is when the ECU sees too much air entering the MAF. It really has little or nothing to do with your actual Air/Fuel ratio. To help with fuel cut you need some bigger injectors and a S-AFC. That way you can fool the ECU into thinking less air is entering the MAF.

 

[kyle h.]

just got 2.5 exhaust with a test pipe, and it fixed the fuel cut. havn't logged it yet or checked anything else.

 

[Eclipsed]

I would suggest slapping on a boost guage if you dont already have one, maybe your boost is running pretty high. Also, what are you using to tune with to get you trims? I would suggest also asking this in the tuning section. Maybe you'll get an idea there also.

 

[RFLTurbo]

With my stock air box my car runs good but when I replace the stock air box with a cone filter I hit fuel cut around 4k rpms and I throw a code. I know its the air filter because when I put the stock one back on, it ran perfect. What do I need to do in order to run an cone air filter without hitting fuel cut?

 

[greeneclipse]

you might need to lower your boost...do you have a boost gauge and controller??

 

[RFLTurbo]

the only mods i have on my car is that air filter and a hks ssqv bov. So if I get a boost gauge and controller and lower my boost, it should run just fine?

 

[calcifer]

Hello, let me first start off by saying that I am extremely happy because my laser is finally among the land of running dsms again. It had been sitting in my garage for about 2 and a half years, and is now running strong again. Mostly. I am having one problem: when at WOT car accelerates great, but when the tach hits 5k, car lurches violently. Is this fuel cut? If I am slightly less than WOT, there is no problem at all, car accelerates strong all the way to redline. There was about a 1/4 tank of gas left in it from 2 years ago, could that be causing any problem? Any way if anyone could help I would really appreciate it. Thanks. By the way, the car is stock, no mods (yet).

 

[BrokenTsi]

i got a 14b if you need one. no shaft play. 120 free shipping.

 

[OnlyNeed4]

ok, i have a big 16g, apexi n1 dp and exhaust, dejon intake pipe, and k&n filter. i hooked up my manual boost controller the other night and took it for a test drive. i get to around 3k rpms in 2nd gear and go wot, it takes off fast until i hit 5k rpms where i think i have fuel cut. the car accelerated fine until it felt like hitting a brick wall and 5k rpms. im new to dsm's, so im not sure, but was that fuel cut, or was i running too rich or what. Some people around town that drive dsm's told me i hit fuel cut, i want to get bigger injectors and pump, but they told me i can over-ride fuel cut some how until i get the money for my parts. Is it possible to over-ride fuel cut? how do i do it? all comments are appreciated

 

[grizzly]

yea you could by turning down the boost, but then I don't think you want to do that now do you. Or if you want you could get a fuel cut defencer, but a lot of people say that it's bad. you could also build your own just look it up on yahoo or something

 

[OnlyNeed4]

i have the boost controller turned all the way down, to minimal boost. i make 9 psi and it hits fuel cut at 5k rpms and a bunch of black smoke shoots out the exhaust. no matter where i set the boost conroller, it still hits fuel cut at only 9 psi, i should be able to run atleast 12 psi shouldnt i?

 

[94EclipseGST]

Check to make sure your timing is not off. When my timing was off, I had very simular problems, with black smoke coming out and fuel cut. Once I adjusted the timing everything was fine.

 

[97GS-TSpyder]

check your BOV make sure its adjusted properly

 

[FunkMasterChipZ]

theres a product out there by HKS its called a fuel cut defender its a computer doohikkie that just fools it into not cuttin fuel www.hksusa.com