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

 

[chrisfrye]

hmm did you hook up your mbc backwards by anychance?

 

[oldman]

Check your plugs and wires then perform a boost leak test, majority or fuel cuts are caused by boost leaks.

 

[lilpastrana]

would that cause it to do with and how could i bypass the mbc i just want this car to run right

 

[lilpastrana]

did i boost leak test has a tiny tiny tiny leak would that still do this? leak is by the throtle body

 

[chrisfrye]

Check your plugs and wires then perform a boost leak test, majority or fuel cuts are caused by boost leaks.

Definitely! do a good boost leak test, i was about to suggest that.

 

[lilpastrana]

does it have to air tight with no leaks at all

 

[chrisfrye]

haha man you guys post so quick. how minor? how quick did you loose pressure? Very well could be the tb gasket..

 

[lilpastrana]

i want to know bad it loses like 1 psi every second or so if that its slow

 

[oldman]

What was the highest level of psi shown on the BOOST GAUGE, not the air compressor, during your boost leak test? How long did it take for it to bleed down to zero after you remove the compressor?

 

[lilpastrana]

15 lbs is all the higher i went. 15-30 sec. to bleed back down to zero or more we can hear the leak its by the tb but can't pin-point it.

 

[oldman]

15 lbs is all the higher i went. 15-30 sec. to bleed back down to zero or more we can hear the leak its by the tb but can't pin-point it.

Spray soapy water mixture on every connection, gasket, fitting.......etc. and retest, you will see bubbles where it leaks. I have done alot of boost leak tests and honestly, I find it hard to believe that you're able to pressurize the intake up to 15psi right after a complete engine swap. I know that boost leak testing is a pain in the arse but you must be completely honest with yourself, 20psi is the goal, it's your car and you will have to deal with the consequences of running with leaks.

 

[chrisfrye]

Seems like a large enough leak to get fix and start there. do you have a peice of vacuum pipe lying around you can use as a "stethoscope" try to pinpoint the sound? haha it worked for me.

 

[lilpastrana]

well we replaced a few gaskets already and we r at 10 boost now. i still don't think that a small leak like that could make this big of a jerk. Also the check engine lite is on at idle then when i push or even touch the gas it shuts off.

 

[oldman]

well we replaced a few gaskets already and we r at 10 boost now. i still don't think that a small leak like that could make this big of a jerk. Also the check engine lite is on at idle then when i push or even touch the gas it shuts off.

Proper functioning of a turbo dsm depends greatly on a leak free system, whether this is the cause of your problem, a leak is a leak and it needs to be fixed.

I would start by going back and double check everything you have done, check cam timing, ignition timing, proper firing order, compression test.....as well as making sure everything has been plugged in.

 

[lilpastrana]

do you have any input on what plugs are easy to forget? could it be the ECU ?

 

[chrisfrye]

Wouldn't hurt to pull your ecu and check the caps and components. While the CEL is on at idle can you try to read the code? (Either with a multimeter,led, or buzzer setup)

 

[oldman]

do you have any input on what plugs are easy to forget?

I'm not understanding what you're asking. BTW please use caps, we are trying to keep the tech forums as professional as possible.

could it be the ECU ?

Yes, but if the ECU was functioning prior to the engine swap, then it's highly unlikely.

 

[lilpastrana]

I have located where it is leaking. It is leaking on the tb where the throttle butterfly it sitcking out, where the cruise/throttle is hooked up. I dont know if this can be tightened or can be sealed.

 

[oldman]

http://www.ca.dsm.org/faq/tb-shaftseals.html

 

[rocknsnoboarder]

Today I pulled my ECU and found some scratches on the board. The ECU was also either repaired or remanufactured because it had a sticker from some place that had done work on it. I also found like a sticky kind of goo on some of the capacitors and other components. Could any of this be a possible cause of my car's problems?

Also wondering where I could pick up a logging cable at. I got a Palm but now I need a logging cable so that I can plug it into my car.
Thanks

 

[Whammydill]

sounds like evidence of capacitor leakage, or the beginnings of it. I'm no expert but if the "goo" or scratches are comprimising the electrical pathways, could be problematic

 

[patty AT forge]

That could be it. As the motor moves it could be shorting out something in the harness.

 

[Dragon TalonTsi]

How much are you boostin? Check your leaks, do a boost leak test. I had fuel cut bad, i couldnt get past 4 1/2 grand, no matter what, even if I stalled or slowly boosted up. I am telling you, check it all out, IC pipes, TB and the Elbow, etc.... better safe than sorry....

 

[talongod]

I'm boosting about 18psi and I took a right hand turn the other day and spooled and got real bad fuel cut and loud backfire. It's only when wheel is cut to right

 

[Dragon TalonTsi]

It could be a number of things bro, just go over everything, and I mean everything! It could be what you least expect too. Back track and trace your steps, cause that is a wierd fuel cut, but hey, let us know how it turns out then....