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

 

[MR2_Turbo]

If the pedal comes back then it is the cable.

Really? If the cable gets stuck, the pedal will still come all the way up? If thats the case, thats great. I can get that taken care of easy.


I forgot to mention that I ordered new oem plug wires and I searched the board here to find the best spark plugs for the motor and decided to get the 1 step colder NGK's. I ordered those as well.

 

[I-luv-em-all]

have you tried removing the lower honeycomb peice in the MAF sensor, that may help a little, and make sure you are running premuim gas.

 

[steve]

The posts that say that fuel cut is airflow based are correct. It's called fuel cut because the ECU cut's the fuel when the mass airflow exceeds a preset limit. All workarounds lie to the ECU about tha actual air mass entering the car. The most common is upgrading your injectors and getting a SAFC or MAFT to reduce the AF signale to the ECU.

Before you do anything else you should make sure that you don't have any boost leaks. That will cause you to have a higher AF signal than normal possibly causing early fuel cut.

Rewiring your fuel pump is a good idea but it won't help with fuel cut. It will help you from leaning out at higher than stock boost levels

Steve

 

[out there]

i also advise double-checking the ignition system. i had plugs that i found out weren't properly gapped when i changed them, my car would do something similar to what yours is doing around 5k. i had all my current mods except the plug wires, and changing from copper .4 (!!!) gapped plugs to new copper .26ish gapped made the car drive much better

 

[Defiant]

Everything you need to know about fuel cut, just like all the other times it's been posted:

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

 

[MR2_Turbo]

i also advise double-checking the ignition system. i had plugs that i found out weren't properly gapped when i changed them, my car would do something similar to what yours is doing around 5k. i had all my current mods except the plug wires, and changing from copper .4 (!!!) gapped plugs to new copper .26ish gapped made the car drive much better

Holy crap! .4 is one hell of a gap! I have yet to check the plugs and I will be just waiting on that until I get my new ones in the mail in a couple days. I'll be gapping those to .28 unless someone suggests a better gap to use. I'm gapping my coppers to .28 on the mr2 and it seems to be a lot better.

 

[out there]

yep, apparently the guy who owned the car before me didn't know plugs needed to be bent before being installed... all thought he at least knew how to take care of the care...

 

[MR2_Turbo]

Another update....


Well, my car is in Illinois with a friend, and I am in Minnesota. After all this happened to him, I had the car flat-bedded to a shop to get a new alt belt put on. Well guess what.... I need a new alternator AND an new water pump! The total is going to be right around $1400 from this shop. Does that sound somewhat normal? Also, the alt was only putting out like 10 amps the guy said. Maybe that was why it would feel like hitting the rev limiter at 5k?


If only the car were here in MN so I could fix it myself :thumbdown

 

[Quasimondo]

Labor will kill ya every time. Unless the water pump is in imminent danger of failing, just replace the alternator and belt, and when you get the car back, you can swap out the water pump and while that's out take care of the timing and balance shaft belts as well.

 

[MR2_Turbo]

Labor will kill ya every time. Unless the water pump is in imminent danger of failing, just replace the alternator and belt, and when you get the car back, you can swap out the water pump and while that's out take care of the timing and balance shaft belts as well.

Yeah the water pump was going to go at any time. The bearings were grinding.

 

[ThaGremlin]

If the pedal comes back then it is the cable.

YOu will know when you hit fuel cut because it is just like hitting a brick wall. I would imagine that your ignition system isnt getting the full voltage it needs to operate. When I had a bad alt I could see that I was only getting about 12.5 volts and after I got to about 4700 and above it would start tp break up a bit. Our ignition systems need a good solid voltage source to work properly.

i get the same problem. . but i usually get it in 3rd, 4th, and 5th gear . .and sometimes in second. . i mean it wont let me pass 5 1/2 RPM. . i still dont know whats wrong. . i mean now i get like this feeling that my car like turns off for a quick second. . the fastest its let me go was 130 and then i get the jerking effect. . any ideas how to fix that. . also when it happens im only at 5 1/2 RPMS . . .

 

[MR2_Turbo]

i get the same problem. . but i usually get it in 3rd, 4th, and 5th gear . .and sometimes in second. . i mean it wont let me pass 5 1/2 RPM. . i still dont know whats wrong. . i mean now i get like this feeling that my car like turns off for a quick second. . the fastest its let me go was 130 and then i get the jerking effect. . any ideas how to fix that. . also when it happens im only at 5 1/2 RPMS . . .

I'm hoping that mine has to do with a weak alternator. I might not have had enough power for the ignition at the higher rpm. If its not that I'll be changing my plugs and wires too and work from there.

 

[oemdsm]

I'm Having the same problems with my car. I hate it. I can't figure out where the problem is. The fuel cuts off at around 3,500 rpm. The car has a rough idle but it runs strong and quick up to the cut off point. I guess if anyone knows the solution to my problem they could pm me or something. BUt as of now I am payin a guy $60 an hour for just trying to figure it out! I'm passed the point of being pissed...

 

[MR2_Turbo]

I'm Having the same problems with my car. I hate it. I can't figure out where the problem is. The fuel cuts off at around 3,500 rpm. The car has a rough idle but it runs strong and quick up to the cut off point. I guess if anyone knows the solution to my problem they could pm me or something. BUt as of now I am payin a guy $60 an hour for just trying to figure it out! I'm passed the point of being pissed...

I will let you know tomorrow if it was either my alternator or water pump that caused it for me. I really hope its fixed now

 

[Darksyne]

I'm hoping that mine has to do with a weak alternator. I might not have had enough power for the ignition at the higher rpm. If its not that I'll be changing my plugs and wires too and work from there.

Fuel cut is a unique feeling that can not be confused with high RPM ignition break-up.

If you are accelerating hard, then all of the sudden feel like you just rear-ended someone then you are experiencing fuel cut. It really is a violent feeling vs. a gradual reluctance to rev that generally indicates ignition breakup.

I really would recommend that you run a boost leak test before randomly replacing parts.

 

[MR2_Turbo]

I really would recommend that you run a boost leak test before randomly replacing parts.

Aye aye captain! Very good advice.



I am really thinking that its the ignition breaking up. What are the most common causes of this? I suppose it could have been my bad alternator, but I wont know that until my buddy picks my car up from the shop. I have new plugs and wires that will be put on as soon as the car gets back here to Minnesota. So from there, I'm not sure what to start checking. I know that this ignition setup is quite different than my MR2.

 

[MR2_Turbo]

and another update:


My buddy picked up my car from the shop today. New alternator, water pump, thermostat, and a radiator flush. Well, the high rpm cut out is still there, but not nearly as bad (i was told). I guess instead of it feeling like its hitting the rev limiter around 5k (i believe before it wouldn't even go past 5k at full throttle), it just stumbles once quickly, then continues to pull through the rest of the rpm band.

I'll have the car back here tomorrow and I'll update again then!

 

[foreverinvayne]

Alright, I'll explain as best I can.

I was driving down the interstate and I was kinda messin with my friend and his 04 Jetta GLI and I was in 3rd gear prolly about 6000rpms and it starts bogging down like misfiring or just not getting a spark (it had been doing this ever since I got the car running again 2 weeks ago) I figure that could be a number of things like not enough fuel getting there from pump or injectors or who fuel filter, or just bad ignition, who knows, but then all of a sudden it seemed like i hit fuel cut, it felt like an explosion, like i hit something and the car shut off. Is the car supposed to shut off at fuel cut? and if so, does it make it not able to start up again for a while? cuz i couldn't turn the car back on, not even at 80mph or even stopped in the middle of the interstate... I go to UTI and I just started so I'm just learning stuff but my friend had been going there almost a year now so he knows his shit. First off he checked all the battery cables disconnected em reconnected em (don't know exactly what for) but he then he said he wanted to check the spark so he took out a random plug wire and told me to crank it so he could see if there was spark. The weird thing is that the car fired right up on the 3 cylinders when it wouldn't right before. And then we just put the other plug wire in and i took it easy on the rest of the way to school and it's been normal ever since, still bogging down in higher rpm's but that's it. always starts fine and everything.

anyone think of why my car does that or what could be a problem with it?

 

[Thunderskull]

Maybe the timing belt slipped some teeth? Did your friend do a compression test? It could also be your coil pack or you may just need plugs and wires. You might want to get a copy of the service manual so that you can do some diagnosis. Did you set of a check engine light when all of this happened? What was wrong with the car before since you mentioned you just got it running 2 weeks ago.

 

[dsm john]

Whenever my car hits fuel cut it feels like hitting a brick wall for a split second then the car starts running again right afterwards if you let off the throttle.

Kind of like if youre hauling ass on a jetski and just let off the throttle completely.

I've never had the car just die completely.

 

[foreverinvayne]

Well, what was wrong with the car before was my clutch blew. And i had replaced the tranny as well. So really wouldn't have much to deal with this. And no my friend didn't do a compression test. I'm gonna replace the plugs and wires tomorrow and prolly replace the fuel filter, some basic tune up stuff... and then maybe see if someone at school can do it cuz otherwise i don't know anyone with a compression test gauge.

And how do you get a service manual?

 

[Thunderskull]

You can usually buy one on CD off ebay. That's how I got mine.

 

[Itzallstock]

Listen to me now and belive me later.
I had the exact problem. EXACT, word for word man. You have a fualty power transister. This casuesd the fuel cut, now since your car wont start you need a new ecu. I know its painful but i replaced every sensor possible on a dsm and that was my casue.
-I'll bet the farm on it
Ben

 

[MR2_Turbo]

FINALLY, she's home. I took it out to see what this ignition break up was. Gave it full throttle in 3rd and around 5k rpm WHAM!!!! Its definitely fuel cut. My buddy told me it was like hitting the rev limit this whole time. HAHA! Yeah right! Freaking violent! I am all too familiar with this feeling thanks to the MR2.

So tomorrow I will be going over all the IC piping checking for leaks and tightening the clamps. Hopefully that will take care of it. So glad to have it here!

 

[Turbo Talon DL]

FINALLY, she's home. I took it out to see what this ignition break up was. Gave it full throttle in 3rd and around 5k rpm WHAM!!!! Its definitely fuel cut. My buddy told me it was like hitting the rev limit this whole time. HAHA! Yeah right! Freaking violent! I am all too familiar with this feeling thanks to the MR2.

So tomorrow I will be going over all the IC piping checking for leaks and tightening the clamps. Hopefully that will take care of it. So glad to have it here!

The Fuel pressure solenoid or fuel pressure regulator wouldnt have anything to do with it would it? Just a shot in the dark. CHECK THE THROTTLE SHAFT SEALS....I got one from a guy on ebay that he claimed was REBUILT. I guess he forgot the new throttle shaft seals. Thats a common problem easily overlooked that u wont find without pressure testing your intake. Mine held 7psi with NO leaks from the throttle shaft seals.