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

 

[Whammydill]

I had a similar bucking and sputtering problem at about 4000+ RPM, it turned out to be my ECU, the capacitors had leaked on the board. You might wanna pull that out and look at it. Its not real hard

 

[CyberEye]

Mines doing the same thing around 4500rpms. Feels more like a really bad missfire than fuelcut. But Pulling the ECU might not be a bad idea.

 

[rocknsnoboarder]

talked to a friend of my dad's that works on domestics and he mentioned putting in an adjustable fuel pressure regulator. can anyone tell me what the stock fuel pump will flow and is this idea worth pursuing or should i just upgrade the pump?
Thanks

 

[Quasimondo]

What are the settings on your translator? If you have it set too rich, it will trigger fuel cut.

 

[rocknsnoboarder]

What are the settings on your translator? If you have it set too rich, it will trigger fuel cut.

the translator is set at 1, 1, 2, 1.
I thought about the translator settings and played with them a few days ago and got not results.

Today I was driving and trying to pay as close attention as I could and may have found that I was diagnosing the problem wrong.
The car doesn't buck at a set rpm but rather when it reaches full boost. The boost is still set at a stock 9 psi, but as soon as the turbo spools up to 9 psi, the car bucks and feels like it wants to stop. If I stay on the gas the rpm's will keep raising but only until hitting full boost again.

Any new ideas?

 

[Dacalvin]

Check The Tps

 

[Rex2342]

Fuel cut feels like hitting a wall. It is possible to hit fuel cut on lightly modified DSMs. My first talon would fuel cut consistantly at 4500 rpm because my boost was to high. The problem your describing sounds more like an improper tune. 9lbs of boost on a 16g is a lot different than 9lbs on a 14b and your probably running to lean. If it's bucking and backfiring/sputtering you need to check your tuning, your maf, or your ecu. Do you have a logger?

 

[rocknsnoboarder]

no i don't have a logger.
as far as the tuning, my car usually runs slightly rich at wot which is why I am so confused as to why my car would be getting fuel cut. Could this be because of the turbo upgrade?
thanks

 

[Quasimondo]

What about the other settings? All dip switches set to "Off"? What position is the AUX switch? Is this a standard 3" MAF or is it something else?

If the settings didn't change anything, look for leaks after the MAF. If you're running in a blow-thru setup, leaks after the MAF will make the car behave like a stock setup that has a boost leak. The turbo will work harder to make up for the lost boost, and all the MAF will see is increased airflow to the point that it triggers fuel cut.

You really need to get a logger, especially with something like the Translator. That logger is the only thing that will give you the proper monitoring so you don't risk engine damage from having the wrong settings.

 

[Rex2342]

no i don't have a logger.
as far as the tuning, my car usually runs slightly rich at wot which is why I am so confused as to why my car would be getting fuel cut. Could this be because of the turbo upgrade?
thanks

How can you be sure your running rich if you don't have a logger? Do you have a wideband or something else to monitor your fuel trims? With your setup 16g, 3"maf, MAFT, stock 450s?, stock fuel pump? stock pressure regulator? I'm thinking your to lean even at 9psi. With the added airflow of the 3" maf your having to richen up the translator which would cause fuel cut but.... Unless you feel like your slamming your car into a wall your not hitting fuel cut. Fuel cut will physically throw you forward in your seat. I've come damn close to smashing my face into the steering wheel from hitting fuel cut at higher rpms !

 

[rocknsnoboarder]

i have an a/f guage. that's how I know that I usually run rich at wot.
like I said, it's just now that the car seems to be running lean and yes that fuel system is completely stock. That's why I was wondering if it might be time to upgrade my pump.
I'm going to go take quasimondo's advice and check out my translator again. I'll post back if I find out anything new.

 

[Rex2342]

i have an a/f guage. that's how I know that I usually run rich at wot.

An A/F guarge is not accurate enough to tune with. Some call it little more than a dancing light show.There is a bunch of articles on this subject just search for them. Pick up a logger so you know what the engine is really doing.

 

[daren_p]

An air/fuel gauge is basically useless in telling if your car is running rich or lean. You really need a logger as your running blind. Doesn't sound like your getting fuel cut, probably a tuning issue.

 

[seth98es]

May seem n00bish, but have you checked your plugs. A lot of misfires are do to fouled plugs, crappy plugs, incorrectly gapped plugs, or even some old corroded plug wires.

Also check for boost leaks, as if you have a bad leak, that will definitely cause this sort of issue under boost.

So your running a stock fuel system correct? Could at least rewire the stock pump, may help if its a fuel related issue. But theres not a way for you to know that since you dont have a way of monitoring the A/F ratios. As everyone else said, the A/F gauges read the narrowband o2 readings and the same thing with the logger, but it gives you better information like timing and air/flow.

Also, since you are a 1g, its definitely worth the 10 minutes it takes to remove the ECU and check for leaky capacitors as if the corrosion is bad, it can cause some very weird issues.

 

[rocknsnoboarder]

haven't posted for a while, but I did try and tune the translator. I increased my maf settings and the car bucked really bad, so I decreased the airflow and the car bucked but not as bad but it's still not running well at full boost.

I did check out my plugs and wires and they were gapped correctly and showed no signs of wear or bad misfires.

any opinions as to whether the problem is more a bad tune or fuel related? Money's kinda tight for the car right now so I'd rather buy either a pump or a logger, rather than both.
thanks

 

[Quasimondo]

Get a logger, and post a log of what happens when the car bucks. When you post the log, show us rpm, tps, injector pulse width, and airflow.

 

[talontsi9095]

Not to sound like a broken record but right now im having the same problem. I did have a boost leak my intake mani. gasket was bad replaced it and now at 4000 rpms i cant go above .5 bar cause the car feels like it hits a wall and studders. The thing is before i replaced the gasket it didnt do this..? i changed plugs and didnt fix it and just earlier i tryed looking at my afc and seeing if anything was changed in my tuning and there wasnt. So i went to leave the house and it didnt want to go at all and the check engine light came on but again i didnt change anything on the afc?? Im stating to think that my car is cursed or that i am! I am about to buy a pocket logger and hopefully this will tell me whats wrong. im running a small 16g with a 255 and 550 injs so i know i should be getting enough fuel.

 

[rocknsnoboarder]

i played around with the translator some more today and found that as i decrease the air I can decrease the amount of bucking the car does near full boost. The turbo also spools up slower with less airflow, which I had anticipated.
This makes me feel more and more like I need to upgrade my fuel system. Can anyone confirm this for me?
Also, can anyone tell me what the stock pump will flow and if there is an inline fuel pressure regulator?
Thanks for all the help

 

[Quasimondo]

Did you get a logger yet or are you still tuning blind? The danger of decreasing the air (especially without a logger) is if you decrease it too much, you start leaning out the air/fuel mixture. If you lean it out too much, BOOM.

 

[talongod]

My car runs fine but on sharp right turns it barely moves and bogs out and hits fuel cut, what can this be?

 

[rocknsnoboarder]

I'm ordering a logger this weekend, any suggestions on what to get?

Also is there anything I can do in the meantime to keep from flying back and forth in the seat every time I hit full boost?

 

[Rex2342]

I'm ordering a logger this weekend, any suggestions on what to get?

Also is there anything I can do in the meantime to keep from flying back and forth in the seat every time I hit full boost?

Turn your boost down! By repeatedly hitting fuel cut your putting a huge strain on your engine. For a logger you'll just need a Palm. I suggest the M515. You can find these on ebay cheap! You'll also need a serial cable. You can either make one for about $5 using parts from RadioShack or pick one up from Ebay or a vendor for about $20-$25. The MMCD software is free from there website. All a fuel pump is going to do is overrun your stock regulator and cause you more of a headache. You could probably get away with a 190lph but since you already have the turbo why not just save up some money, go all out, and upgade to a 255lph, AFPR, and bigger injectors?

 

[oldman]

Stop playing around with the maft, return it to stock 450 setting and perform a boost leak test.

 

[patty AT forge]

I've seen something like this twice before, both times on cars with distributors. Turned out the dist plug had a short in it...
Maybe something similar is happening with the CAS plug?
Does the car only do it when your are turning or will it happen if you are parked and turn the wheel all the way?

 

[hottboost]

When you go around the sharp turn does your clutch loose preasure??