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

 

[slodsm]

knock sensor would have nothing to do with it, the boost leaks however a huge contributor. One more time, fuel cut is only when the maf has reached its peak flow of air it can count, in otherwords overrun. Then it cuts fuel. Nothing else will cause it, not a fuel pump, knock sensor, faulty injector, nothing. Only the maf count. You were reading more air than your engine was getting becuase a lot of it was leaking out causing your problem. Most likely it will be golden now when you have the new IC in it.

 

[IHeartTurbo]

Ok, well I was told the knock sensor could have something to do with it. But anyways, when getting fuel cut I should be running a little rich right? Well, I'm not. I'm actually running pretty lean. Am I retarded or is something wrong?

 

[A016]

Well I am looking at yet another car. It's another 92 Laser AWD turbo. 6/4 with 132k miles. New clutch and rebuilt trans with only a couple hundred miles on them. It is bone stock and there is a problem. He is getting fuel cut. I'm not too familiar with fuel cut and he says its probably the fuel pump or injectors. I was wondering if I bought the car and got a new pump and injectors if that would take care of that problem. It looks like I can get the car for about 2k. I was wondering what would be the biggest pump/injectors to run on the stock 14b or what would run the best.
Do you think it would be worth it? Please let me know your thoughts.

 

[dave99gst]

IF its bone stock it aint fuel cut -- but for argument sake. larger pump+injectors dont eliminate it ... it just pushes it back.

 

[A016]

if its not fuel cut, what would the problem be. if u got a while to talk dave, A0burkell on AIM

 

[Spellmen]

Are you sure it's bone stock? Is it possible he has the boost turned up a bit? If it is bone stock, then it wouldn't be fuel cut.

 

[A016]

The only things that are new are the rebuilt trans and clutch and he said he got a new/used 14b. The timing belt also needs to be adjusted.

Link to the ad: http://www.gopartstrader.com/cgi-bi...ion=display_sub_list&session=40154e5c79329fb6

 

[psychlow]

Originally posted by dave99gst
IF its bone stock it aint fuel cut --

I disagree. Two conditions can cause fuel cut on a stock DSM (epecially a 1G, which has a non-POS BOV):
1) Massive boost leak (most likely)
2) Wastegate rusted shut or disconnected actuator

Both should be (fairly) easy fixes, unless it's a boost leak between the intake mani and the head, which is just a minor PITA.

 

[paranoidTSi]

fuel cut happens when the ECU feels there is too much air/fuel coming in and it violently shuts your car off.

if you mean fuel effeciency, then yes you are going to lose some it boosting your PSI means more air, more air means more fuel required..thus you'll lose some MPG.

The fuel pump shouldn't do anything in terms of MPG unless your turbo is swapped, and the pumps true benefits are taken effect (sending more fuel than the stock one could provide). Putting an aftermarket fuel pump in a stock configuration will not take anymore gas than the stock pump because the demand would still be the same.

In short, upping the boost will take some MPG away, the fuel pump will but only if your car requires more gas than the stock one could pump.

 

[Jason_99ozGS]

Originally posted by NeOzz1
u have an estimate on how many mpg i will loose with more PSI and if i get fuel pump and 16g how much would be lost

It all depends on how hard you're going to drive the car. If you hit boost leaving every stop light then your gas mileage will suffer. If you take it easy without really hitting boost too often I doubt will will notice a difference.

 

[GrahamT]

Originally posted by Jason_99ozGS
It all depends on how hard you're going to drive the car. If you hit boost leaving every stop light then your gas mileage will suffer. If you take it easy without really hitting boost too often I doubt will will notice a difference.

Of course, you could install one of the lo-hi boost controllers if you are worried about economy and only want to have a boost on special occasions.

http://www.dsmtuners.com/parts/product_info.php?cPath=2_138_30&products_id=403

Think that one even comes with the nifty "rocket launch" style covered switch.

 

[manuel2063]

My problem is when my car reaches boost of 15 - 17 psi the fuel cut comes on. I dont have the boost solenoid hooked up. Im currently running the following,

94 Octane
Air Intake
3" down pipe
3" exhaust
Walbro 255 lph/HP fuel pump
FMIC
Big 16G
Ported O2 housing
Manual Boost Controller

Thank for your help.

 

[gsxtasy91]

well you said nothing about tuning or even that you changed your injectors so its kinda a hard problem to diagnose with the info you gave dude.

 

[Newlogics]

While on the topic, here's how to go around fuel cuts:

Since fuel cut is ECU-induced, to avoid it, ECU needs to be fooled about how much air car actually draws.
Using SAFC is a good way. MAS bypass tube is cheapest way. Once you fooled ECU into thinking that you're not drawing as much air you really are, now you need to fool ECU into supplying enough fuel (since it will only supply fuel for the air that it 'sees')

That can be done by several means: Higher-flowing fuel pump, Bigger injectors or Higher base fuel pressure.

Whichever way you do it, make sure you have means of keeping an eye on what's going on with your mixture. (Logger is a good basic tool)

To summarize:
Air: Increase un-metered air/ reduce meter reading
Fuel: Increase fuel flow.

 

[Boosted19]

nah FCD's actually work, i installed mine, and i get no fuel cut. only when i first start the car up, i know i know, your not supposed to make boost when the car is in warmup yet...but im going with the 2g MAF and 550cc inj. i should be fine then.

 

[95GSXBLUR]

My MODs

Extreme PSI polished intake
Dejon Tool Upper intercooler pipe
1G BOV
Hallman Pro MBC


I bought a Walbro 255 - even if I put that in, I'll still have a problem with Fuel Cut when I raise boost levels? How do you guys NOT hit fuel cut with 20Gs, 14Bs, and 16Gs?

I can't afford an S-AFC or else I'd get one..But I heard it could still be a problem even if you get one. Should I leave the boost around 12, and get a turbo back exhaust first or should I get the S-AFC?

 

[drillo99]

you need the cat back first, the s-afc is not till later if ever for you, I say that because you have a 95, if your ecu is a eprom one then your way better off saving a little more and getting dsmlink which would also get rid of any future fuel cut problems and give you much more tuning options.

 

[midnght]

Originally posted by JessesTalon
you should not be boosting 17 psi period, u have no fuel mods!!!
no wonder you get feul cut, you shoudl turn it down to 14-15 max...

Wrong :thumbdown

So you have done this before

As per the secound rule in 'When replying to a discussion' I have done this. Matter of fact I ran it like that for about 4 months. Not once did I hit fuel cut. When I put the 20G in I checked for play in the T25 and found what would be expected from a 35,000 mile turbo. Very small at best.

I am not saying for everyone to run it like this all the time. But if you turn it up for a night and find your limit for your 'fuel cut' then do it every once in awhile. I ran it like that EVERYDAY in EVERYDAY driving. This is my daily beater and I don't plan on making it a JEWEL that is not to be pushed to the edge.

 

[midnght]

And that was at 19psi

 

[doug]

Originally posted by dave99gst
injectors, pump etc just puts it off.

Technically, it's the "etc." part of this that puts it off-- an S-AFC. A pump or injectors will not affect the onset of fuel cut. It's caused by the ECU seeing what it thinks is too much airflow through the MAF, so it decides that there must be something wrong and cuts fuel to the engine momentarily. An S-AFC fools the ECU into seeing less airflow, therefore pushing fuel cut farther out.

Many people (me included) don't see fuel cut until they upgrade the turbo, which enables lots more air to be pulled through the MAF.

 

[dave99gst]

Originally posted by GetEvryGear
He isn't a long way from it... if he turns up the boost too high that is where he will get the fuel cuts. Just be smart I get fuel cuts when its really cold outside... because I don't have the boost controller on yet. When its cold, my boost is at 17 psi and it cuts in 3rd and 4th gear.

welp im at 20 psi on a modded 6bolt b16g big greddy fmic and have yet to see f/c .. so ya hes a long way from it.

 

[doug]

Originally posted by dave99gst
im at 20 psi on a modded 6bolt b16g big greddy fmic and have yet to see f/c

Maybe some cars are different. I saw fuel cut at about 15 PSI as soon as I installed my Big16G. But oddly enough, not for a few days. There are several variables that factor into the ECU's decision as I understand it, however, including stuff like IAT.

 

[greenmachine97]

I have done plenty of searches. and it soudns liek fuel cut but everyone else says that with the mods i have i wont be getting fuel cut. so i decided to go ahead and post anyways, because this scares me. so far it has happened to me 4 times, twice today!

i am traveling along at like 50 and i punch it hard while in third,
the boost builds real fast, then all of a sudden(no where near redline), the car violently jerks real hard, like something stopped my tranny. it scared the shit out of me! i thought i lost the tranny for a second. but then after that it drives fine. i did it again today. same thing happened! i wasnt watching the boost guage very closely, but i imagine it was around 17 or 18 when it jerked.
i dont have a MBC yet, but usually my boost: spikes to like 19, settles down at like 15, and then gradually starts climbing back up. i havent ran it past 6000rpm, so i dont know what it does past there. but today i think it was staying around 17psi.

my engine mods are as follows:
Greddy intake filter
Greddy upper and lower intercooler piping
Greddy Type-s BOV (vented)
Greddy EVO Catback (3.15")
Apexi n1 3in. downpipe(no cat)
Autometer A/F and Boost guage

oh, and how reliable are the a/f guages? if it says i am running very rich under constant full boost(15psi), could i actually be running lean? and i am getting a Greddy MBC and a 190lph fuel pump. do you think that this will help any of my problems much: spike, creep, fuel cut?
thanks in advance

 

[greenmachine97]

thanks for the replys, and i did search. but i wasnt sure that with my current mods, that i could be hitting fuel cut. and will a 190lph fuel pump help this at all? cause i am getting one of those soon, does that sound right for my next mod? and i am getting a MBC asap also. will that help the fuel cut after i turn down the boost? or do i need to get an safc for that? and is an safc worth it? or is a datalogger the best way to go?

 

[tlnpwr]

Originally posted by greenmachine97
is an safc worth it? or is a datalogger the best way to go?

safc is definitely worth it. datalogger is great for monitoring things like a/f ratios. but safc will allow u to make adjustments. i would think to get a safc & MBC before a bigger fuel pump. but i could be wrong. maybe someone else can chime in on this?