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

 

[CrzyTalonAWD]

I have a question. I have been running 20psi with a walbro 255 and a turbo XS fuel pressure regulator (stock injectors) however these past couple days my car has been acting up. If go WOT until about 5500RPMS the car will cut out and almost back fire. However why did this just start up when ever sence i baught the car its been at 20PSI i have never ever had any problems with this sence. sometimes it will go all the way to redline other times it will cut out and sound NASTY.. i have no control over the boost level its a external wastegate and im using about a 1.1 Bar, i have a Joe P boost controler however im waiting to go see a friend of mine to install it and help me tune my car. but if i am getting fuel cut then i will have no choice other then to change my boost level.
Thanks for the help

 

[1WheelDrive]

Have you checked your plugs. Sounds strange but I had a similar problem, turned out one of my plugs was fubared.

 

[SpoolnTsi]

Theres alot of things that can factor in on how a car performs. Like elevation level, outside temperature, intake air temp. and so forth. You can tune a car to run like a champ when its cool outside like say 50-60* but come a warm and humid day say 80* the car is going to hit knock and run like shit. All cars run there best when its cool out and the air is dry. Elevation has a part in it too. One factor that needs to be addressed with the car is the injectors. The stock 450's are insufficient past 18lbs of boost even with a 255 pump and regulator. If your running the stock SMIC, they will only handle so much also. 18lbs is about the limit depending on the turbo. So here are some options. You can turn the boost down, or if not, you will need to consider upgrading your injectors to 550's or maybe 650's depending on what turbo you have, and the IC to a FMIC or a larger SMIC. You can probably get by with upgrading the injectors for now until you can upgrade the SMIC but that would need to be the next thing to address after the injectors

 

[blcknspo0ln]

you're running 20 psi on JUST a pump

 

[CrzyTalonAWD]

well its really not my fault that im running 20lbs of boost.. its actually 19.5Lbs. i baught the car like it is. I just baught a boost controller and a bunch of other things like SAFC and Tunerstien(freeware) but the palm and the 13-006 from Multiplex-engineering , and a couple more supporting mods. I will however check the plugs and make sure they are alright. Thank you all for the help ... is that really bad to be running such high boost on stock enjectors, if these are supporting 20LBS of boost why upgrade.. however i have found some Lucas 550's are thoes any good? thanks

 

[CrzyTalonAWD]

i also have the B16G ported and polished with the fins clipped 15degrees. and yes i am running the stock SMIC if anyone has a supra SMIC let me know!!
Thanks . also can someone fill me in on these lucas injectors?

 

[95gster]

yes I have the lucas 550 and they are fine for your setup they are the same as rc 550 injectors except cheaper hope that helps......

 

[rcjohnson86]

1997 Eagle Talon Tsi, I just completed swapping a JDM Galant VR4 motor in, to replace my original 2g which gave me the finger. Well everything went smoothly installing wasnt that hard, no check engine lights or anything, I used the entire 1g, intake manifold, exhaust manifold, turbo, and cam angle sensor. Well when I took it out to test drive it, when I was under full throttle it felt like hitting a wall at 4k-5k rpms at full boost on the stock boost guage. It feels a lot like a fuel cut, like the one you hit when your topping out a car. Any suggestions?

 

[halik008]

check ur Boost control solenoid hoses..... ne is suppose to go to intake the second is suppose to T off with one end to the compession housing and the other ot the wastegate..

halik

 

[rcjohnson86]

The turbo does not have a place for a vacuum line connection, the only place for one is on the end of the wastegate, do you think this may be my problem? Im pretty sure its a 14b turbo, I looked and looked for a place to connect a vacuum line to the turbo but there isnt one. Also it appears that the arm going to the wastegate is rubbing the turbo, so should I fix this problem too, could that be causing it to cut fuel at high boost/rpms ?

 

[halik008]

well if there is not nipple on the compression housing for the other end on the T'ed hose then you cannot use the stock BCS....

I know what for a fact since when u had to pulg my BCS back in due to defective MBC i forgot to hooke up the other T'ed end to the housing and i was getting huge power loses similar to huge fuel cuts under heavy accelereation in high RPM'a


halik

 

[rcjohnson86]

Well I had an idea, can i mount the stock 2g, I think its a T-25 or T-28 housing on the 14b? So I would then have the vacuum line hookup and could get rid of the jpipe?

 

[halik008]

two totally different turbo's

just get $20 MBC....

halik

 

[mnexcited]

This is on a 90 GSX, w/ free mods MBC 2.5" turbo back. Otherwise stock, the car runs 15 psi all day but lately I've been getting fuel cut either down shifting into third, or sometimes 2nd off a launch. Does not have to be WOT and will always correct itself. Meaning if I keep it to the floor it'll fuel cut catch and go fine. Any ideas?

 

[TheTSiGuy]

15psi on stock is too much

Put it on 12-13.

Bother to look at his profile?

He's not too stock there buddy.

How are your MAFT settings?

 

[mnexcited]

There are some other things that may help w/ this problem. Car has trouble starting after it is warm and sits for about 15 min. Timing is right and plugs and wires are brand new. Also it sometime boost spikes to about "23" psi then settles to 14 to 15. Done this since day 1 but I've never had fuel cut. Also WOT is 3 to 4 bars in the green on a/f gauge.

 

[TheTSiGuy]

Bother to read his statement? Its for a 90, not his car. Jeez

Wouldn't hurt to do a boost test, maybe find some vacuum/boost leaks.
I have ran 15 on a stock system to see what its done, mine didn't hit FC, not even at 7200.. you could be having a vacuum problem through a hole or what not.

My apologies. Was skimming through the post, and didnt catch that. :embarrassment:

 

[mnexcited]

That's cool. My car runs fine this is my G/F's car. It's hard to say what she does with the thing all day. I can't figure out the thing and I'm getting sick of her Bichin.

 

[FutureGSXOwner]

You said the plugs are new but which ones are you specifically using? I've seen so many fuel cut problems solved by changing the spark in one way or another (gapping, material, and ovbiously plug heat range).

 

[mnexcited]

NGK 7es's at .030 gap. About a week old.

 

[bosljeff]

Has there been a significant drop in temp lately? The cooler, more dense air can possibly be a cultprit. Just a thought. If you are running just barely too much boost, it may be fine and dandy during warmer temps, but that barely too much boost can become too much when that temp drops.

My .02

 

[mnexcited]

It's been really warm latley. I'm gonna turn the boost down alittle and see what happens. Let you know tonight what happens.

 

[TheTSiGuy]

It's been really warm latley. I'm gonna turn the boost down alittle and see what happens. Let you know tonight what happens.

not that it matters, but i've always gapped my plugs to .27-.28

 

[doug]

I use .028 myself.

The warm start problem may indicate a problem with either the FPS or one of the vacuum hoses running to/from it. Whether that can cause a fuel cut type problem, I don't know. However, I've been running completely without the FPS for well over a year with no starting problems, even here in SoFla.

 

[Defiant]

It's fuel cut but WHY?

http://members.shaw.ca/costall/ECUprimer/ECU_ch7.html