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

 

[firebirdvert305]

Oldman...can u tell me if i hit fuelcut (i originally made this post to see if i can relate my experience) ....well i was coming off an onramp at 50mph in 3rd gear...it was 55 degrees that night...it was 4am in the morning...cold as hell...and i decided noone is around, im merging on the highway why not lay into it? Well i did....well i also got my MBC set to 15psi...but the 3" exhaust is making it creep...so i smashed it...and i see that it crept upto 18psi...i was at about 5500...then all the sudden i heard a loud POP...or a backfire (dont know which one)....the car suddenly died for a second...came back 1 or 2 seconds later.. so hard the tires chirped...i immediatly pushed in the clutch and coasted down the highway....Put it back into 5th gear and drove home ever so calmly....My car has never done this before...i put on david brode piping not too long ago (licp, compressor outlet pipe,uicp, bigger elbow) .....il be doing a boost leak check this weekend...Oldman did i just describe fuel cut to you with my story?

 

[Insane4ceFed]

Will do a boost leak test. I think there may be one because at high boost or 7-10 I can hear a whistle , but the car has a fairly good size turbo so I didn't want to mistake it for turbo spool.

 

[oldman]

il be doing a boost leak check this weekend...Oldman did i just describe fuel cut to you with my story?

Very much so. Fuel cut occurs when maf registers too much air so the ECU cuts the firings of the injectors to protect the engine. Boost leaks, boost creep and run away boost are some of the most common causes of fuel cut. With that said, I believe you have both leak and creep because 18psi is still way too early for fuel cut on a 14b even on a cold day. We should turn this into a "everyone do a boost leak test thread".

 

[ForceFedRed]

First time I hit fuel cut, I was looking in my rearview for my transmission laying in the street. Was gunshy of WOT the rest of the day until I figured out what the hell happened.

JRM

 

[firebirdvert305]

Hey oldman ...u said boost creep, boost leak and "run away boost"...can u explain run away boost for people who may not know such as myself

 

[oldman]

Hey oldman ...u said boost creep, boost leak and "run away boost"...can u explain run away boost for people who may not know such as myself

Test run with the actuator nipple open and you will know what I mean.

 

[firebirdvert305]

the WG arm cotterpin broke...and came off....car didnt build any boost at all...so run away boost would be a uncrontrollable amount of boost...that will kill the motor.

 

[oldman]

Test run with the actuator nipple open and you will know what I mean.

In case if you took me seriously. Run away boost usually is caused by problems with mbc/actuator causing the flapper not to open resulting in infinite boost level.

 

[SolidBoostTSi]

just to add to experiences, the first time I had fuel cut i Sh*t you not I though GOD slapped me in the back of the head and i pulled over on the tollway thinking I blew my HG. And about a month after, the hitch pin fell out of the actuator arm on the same stretch of high way. Now I use a cotter pin like the ones on the shifter cables and since then I've been reluctant to run on that darn high way.

 

[wallyman]

OLDMAN, How quick is a wastegate supposed to open? I've tested mine and it opens at 12psi but slowly.

 

[wallyman]

Can someone provide a link for a boost leak test procedure? Thanks, I would search but I have to go to a meeting.

 

[98RedGs]

http://www.vfaq.com/mods/ICtester.html

Here's your link.
If you can't pull it up lemme know!


-Thank you
John

 

[wallyman]

Thanks! i appreciate it.

 

[Defiant]

Yeh. Please do not use "u".

 

[my98GST]

not to jack the thread, but what is boost creep and what does it have to do with fuel cut?

 

[oldman]

OLDMAN, How quick is a wastegate supposed to open? I've tested mine and it opens at 12psi but slowly.

The important thing here is that it opens at 12psi and the arm extends fully to open the flapper all the way. Obviously if it take 5 seconds to open then it would be a problem, are you having boost controlling issues.

not to jack the thread, but what is boost creep and what does it have to do with fuel cut?

In short, you should do a search on your own as well, boost creep is when you intially hit your desired boost setting, hold for 1/2 second and continue to creep up as rpm increases. A different form of run away boost if you will, caused by the wastegate's inability to re-direct air flow in order to bypass the turbine.

 

[wallyman]

The important thing here is that it opens at 12psi and the arm extends fully to open the flapper all the way. Obviously if it take 5 seconds to open then it would be a problem, are you having boost controlling issues.

I'm having fuel cut issues similar to the situations stated above. I am not sure whats creating the issue. I'm going to do a boost leak test today after work and a fuel pressure test. I'm also looking for alternate causes for the problem if boost leaks are not it. I don't have an after market gage yet but I'm pretty sure that the needle shouldn't be sticking on the stock 14psi mark when I'm in the throttle. It seems like i am over boosting but I'm not sure. They're is no boost controller or any other mods the car is COMPLETELY STOCK. I need to get a baseling before i can start modding.

Thanks for the help.

 

[oldman]

Is your profile updated? If not please do so. It's possible that you either have boost creep or run away boost and a boost gauge is needed to confirm this, how will you perform a leak test without a boost gauge anyway?

 

[wallyman]

Is your profile updated? If not please do so. It's possible that you either have boost creep or run away boost and a boost gauge is needed to confirm this, how will you perform a leak test without a boost gauge anyway?

My dad has an exteranl regulator with a pressure gauge. I can set the regulator at 16 psi and run my test from there. I should be able to hear leaks and watch the pressure gauge drop if im leaking. I will up date my profile.

 

[project_tsi]

Yeah, turns out I had a major boost leak at the t-body, and along w/ the creeping, was hitting cut pretty quickly. Although, that was a LONG time ago, I don't even have that setup anymore.

 

[dmndstrsfrevr80]

Yeah, so I got my a$$ handed to me by a souped-up Cutlass last June because I kept cutting out @ 5k with 15lbs. of boost. The friend who installed the HKS fuel cut defenser, showed me a dial connected to the unit and adjusted it. We took it for a test ride and the car flew like new. When I looked at the dial, it started at 1000 and went up in 1000 increments to 9000. He said it was set at 5(k) when it was supposed to be set at 7(k). I asked if this was RPM increments. He says "I don't know..."
"How the hell did you install and set this thing, then?" Does anyone have any idea what I'm talking about? And if you do, am I right about the RPM increments? It makes sense...kinda like an MSD boost retard unit...those are usually set in 2000rpm increments...what's the scoop?

 

[DSMstatus]

ive never seen a fuel cut adjuster, though ive heard of them, but that sounds more like an air flow controller to me. thoes should be rpm increments. be very careful adjusting them, you need a logger and knowledge of them or you should have them 0'd out, you could seize up the engine very easy if misadjusted.

 

[HyperGSX]

When it gets really cold out at night, i will floor it and the car will go for a little bit then BAM it feels like the car just stalled. I have minimal mods, and i do a have an MBC, but its tightened all the way down so im usually at only 10-11psi anyways.

 

[h3o]

what do you mean when you say "cold" it could be that the cold air is bringing in a dense mass and your just getting too much air, but then again i could be wrong

 

[HyperGSX]

well im the chicago area so its drop 20 degrees between early afternoon and evening time