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

 

[ZenkaiRacerDsM]

A while ago when I first installed my boost controller I had it in backwards. So the boost would just climb like crazy. It went up to around 23psi. It looked like it wouldve went higher had I stayed on the gas but once I noticed it climb so high I let off immediatly. It never did hit fuel cut. Also Ive while I was adjusting the bc I had it at 18psi on one run. This time I was at WOT for a lot longer. Still no fuel cut. I probably wouldve left it at 18psi but at the time I had a bad coilpack and it was giving me a slight hesitation. I thought it was my car detonating on me. But it kept doing it even at stock boost. I have since changed out the coil pack and it runs nice and smooth now. I am curious as when it will hit fuel cut and why it hasnt. Right now Im at 16 psi. When I bought the car I was told it had a walbro 190lph pump in it. Anyone else think its weird Im not hitting fuel cut at those levels?

 

[white95tsi]

I've made myself a boost leak tester, but I haven't tried it since the major problems. I'll try it again tomorrow and see if thats what is causing my problems. I pretty much can't get any boost at all right now, once it spools, it just craps the bed, so I have to shift at about 2800 rpms or I hit fuel cut. I'm gonna buy a new fuel filter tomorrow, and throw it on just to make sure that isn't causing it also.

 

[blcknspo0ln]

well of course do one thing at a time. so this way you know what was causing the problem and you'll know how to fix it may it happen again g'luck

 

[Defiant]

Fuel cut is brought on by intake volume, not boost levels.

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

 

[ZenkaiRacerDsM]

Hmm... I havent checked to see if my maf is hacked yet. I will do that. If it was hacked wouldnt I be able to tell by the way it drives and idles?

 

[MattnGsx]

Get a logger ASAP. How do you expect to tune it without one? I bet your injectors are being maxed out.

Ok I fixed the problem, and I always like to keep updated so if someone else has the same problems they can look it up.

No i don't have a logger, but a wide band and egt works just as well for tunning. Though it would be nice to know what the ecu thinks too.

Though anyways I finaly got to putting in my 650cc injectors, but the fuel wasn't the problem it was actually my coil pack voltage didn't match spec. So I replaced it with my coil pack off my other motor, adjusted fuel and it ran great!!!

-Matt

 

[wagman]

try checking the ground wire that goes from the ecu to the fuel pump relay, tats what was shutting down my car...hope this helps

 

[Cooljock]

Ok, I have a boost guage and it goes up to 17psi if the air is cold and when it warmer 13-15psi this 90f and when it does I go no where and my exugest tone gets real deep and loader ( it sound good and cool ) and all this started after I put my down pipe on. everything in my info is uptodate. After reading all the post and everything I through out the idea of using a hks fcd. Now im thinking about a safc I want to try to keep with hks for the majoity of my parts I have about $400 to try to fix it right now. Then I called mach v and they said to fix this prob to put a boost controler in. I would like to start raising my boost. im getting a/f guage this week hopfully. so maybe it will tell a little more of the story. I would like to buy item that I can use for the long run and not quick fix like a fcd ( as I understand it to be).

 

[Cooljock]

would the hks F-CON navigator serve the same purpose as the safc?

 

[98spydert]

Something for the long run that will make sure you won't get fuel cut? Get some bigger injectors and correct the air/fuel with an SAFC or HKS' version of it. no more fuel cut, more fuel for the long haul.

Am I getting this right? Your car is making boost and sounds like it's making power but you're not moving? Sounds like a clutch spinning agianst the flywheel to me unless I'm missing something. Are you're RPMs shooting up and you're just not going anywhere?

 

[saw22]

Hey everyone, I know the issue of fuel cut has been beaten to death in here, but I cant seem to find exactly what Im looking for. I just had my stock cat replaced with a 2.5" straight pipe Monday. I was cruising around last night and got on it at about 50 in 3rd and hit fuel cut at about 60-65.

I think I remember reading a long time ago that installing a straight pipe can cause your boost to creep up on you.. so I (gently) hammered it again (if thats possible) and watched my boost, which was on about 14 psi go from 14-15-16-17, gaining about 1 psi per 1200 rpms. I left off in fear of hitting fuel cut again and starting messing with the MBC. I seem to have it under control now.

But anyway, is this really common? Another related occurance is hitting fuel cut if I get on it and the car has only warmed up for about 10 minutes.. in fact, that was the case yesterday too. Seems like that would be long enough to me, driving in 75 degree weather, but maybe not.

My other mods are 2.5" catback, UIC pipe, MBC, K&N, free mods, ported 14B. Got a Walbro 190 just yesterday, looking foward to that install and hoping it will help my problem.

Any feedback would be appreciated!

 

[Cooljock]

thx for the info but my rpm are not shooting up, it just sound like it acc. but im not going anywhere and the rpm arnt climing very quick they are slow when i shift into secound then heck yea. btw it doesnt happen all the time it maybe once out of every 8-10 time I got to get on it

 

[zerok318]

Ok, i just did a 6 bolt swap in my 2g. everything seems great but i have one big prob. It runs pretty rich. these are the things i've done to the motor since the 6 bolt swap.
1) bypassed the evaporative can
2) still using the wastegate silonoid
3) evo3 16g turbo
4) balance shafts removed
5) fact. fuel system and injectors
6) maf screw flush for more air flow.
7) new o2
8) apexi n1 exhaust/ RRE downpipe (no cat)


The thing is i have the air/fuel gauge reads all the way rich and once the turbo starts to spool at 3k as i barely give it any gas it feels like fuel cut because it back fires a lil' bit and slows the car down.

I have it timed right. with the cam sensor, used a timming light. I could it be my fuel regulator? But how would i test it.

 

[SuperSleeper]

There are a couple potential solutions to your problem.
1st and foremost, I would recommend porting the O2 housing. (get a 2G housing if you can) Opening that up a bit will more than likely eliminate most overboost occurances.
Secondly, rewiring the fuel pump wouldn't be a bad idea. Installing the 190 would obviously help too, but you won't overrun the FPR with a rewired 190, so why not?

 

[SuperSleeper]

Does it feel like it's running rich all the time? Maybe the A/F gauge has a weak ground... that'll make it read rich.
Otherwise, wondering if you are venting the blow-off valve. That could throw your stoichometry off a bit, as we all know.

 

[saw22]

Thanks for the information. I played around a little more with the MBC and got it set back where I had it. Now it stays at 14 psi in 1st, 2nd and will go to 15 in the top of 3rd. No more high-spiking. I guess taking out the cat added just enough more flow to make me adjust the BC.

Oh well, seems to be working now!

Thanks again!

 

[zerok318]

yea, i know about the venting my bov. I have it recuirculated. But i was think'n when my buddy and i installed the n1 system my buddy said not to install my new o2 in the back (something about if its hooked up i'll have a cel until i get a resistor due to my lack of a cat) so i have the 02 in there but its not hooked up. could this do it if so then i think i know what the prob is. thanks for your help man

 

[SpeedFreak03]

If the upsteam O2 is still installed (before cat) then it shouldn't affect your A/F ratio. But if that sensor isn't installed or hooked up, the ECU will automatically adjust fuel trims to make it run rich, to avoid any possible damage (the ecu is running "blind" about the A/F ratio when the upstream O2 isn't installed, so it just runs rich to be safe).

 

[zerok318]

If the upsteam O2 is still installed (before cat) then it shouldn't affect your A/F ratio. But if that sensor isn't installed or hooked up, the ECU will automatically adjust fuel trims to make it run rich, to avoid any possible damage (the ecu is running "blind" about the A/F ratio when the upstream O2 isn't installed, so it just runs rich to be safe).

i have a new o2 sensor in the o2 housing installed. but i dont have the one installed after the straight pipe. I'm wondering if that o2 sensor is affects my air/fuel mixture

 

[zerok318]

Or do you guys think it can be my coil pack because when we hooked them up we had the wrong connector hooked up to coil pack at first (think it was the Ac). It looks as if the third plug might have melted a lil' from what it looks like, but i'll test it tomorrow i guess. But i only have this prob once the turbo starts to spool and thats right at about 2500-3000rpms and cant go past that.

 

[zerok318]

ok i tested my sparks with a working coil pack from my 2g motor. thats not it. could it be my rear o2 sensor. I noticed when i drove it down the block and parked it i smelled gas. its that rich.

 

[zerok318]

it wasnt the o2 sensor in the rear. I was looking at the timing and some how it was like 25g.retarded. but last night it was at only 5g. retarted. wtf. and it was idealing really high (2.5-3k) last night and today but when we first timed it, it idealed with no prob. I need help bad. please someone give me some advice

 

[Parsalian05]

about 2 weeks ago i noticed i was hitting fuel cut around 4k rpms (the rpms would stop climing for a couple seconds when boosting, then start to go up again). this wasnt a huge suprise since i had installed an intake prior to the problem, so i figured rewiring my fuel system would help... well it didnt, it actually seems as though the problem has gotten worse.

the night after i rewired it, i test drove it and found that the idle was very low and after hard acceleration, the car would even shut off sometimes. after about a day the idle went back to normal (im not sure how dsm ecu's work but maybe it took a little time to readjust the fuel system) but i was still hitting what i thought was fuel cut.

just a couple days ago though, i was accellerating hard up a slope while in 4th gear, at 3.5k rpms, i got that "fuel cut" feeling for a second then the rpms shot up unusually fast and i smelled that kind of burnt clutch smell (like when you go too fast in reverse). the thing is, my clutch is fine, it never slips when shifting and my car only has 95k miles...

im just wondering what might be causing this problem. fyi the only mod on the car is the performance air filter and the rewiring.

please help

 

[sc2_ct]

Sometimes when I'm driving and hitting around 13 psi, I'll hear a thumping/droning sound coming from behind me, and the car will quickly lose power. I am assuming that this is the car hitting fuel cut, but don't want to go rushing off the wrong path just to find out it is something else.

If it is hitting the fuel cut, what is the best way of dealing with it? I know I can hack the MAF, use a FCD, or any number of things, but I was wondering what people have found to be the best way to deal with it? Any suggestions appreciated.

 

[sc2_ct]

Sorry, I thought I already changed the vehicle profile, but that must have been on a different board . What kind of mechanical problem would allow normal acceleration without any problems and have this kind of symptom? I've never dealt with AWD, so might it be something in the center or rear differentials? I just refilled the rear diff with synthetic gear lube and it looked to be in good shape. Any other ideas on what the problem might be?

It is a pretty strange noise that I've never heard anything like before.