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

 

[Boost95]

Haha, I shouldn't have said that either, My girlfriend will probably log on later Ya I just got the new ISC in so IM going to run another test as soon as im done eating. I will post up in a few with what I get. Im doing this myself so I gotta pressurize it run check the gauge etc etc. Thanks for the help in advance

 

[Boost95]

I still cant pinpoint it. I tested from the TB elbow. Its not a loud hissing sound liek most leaks are. You know what it sounds like if you have Natural Gas in your home and the heat is coming up and it has that sound to it Kind of hard to explain a sound in words. I can hear it more in front of the TB than in the back and its near the center of the intake manifold. I cant find any leaks at my IM gasket. Would that EGR still be causing any problems. All I have now is the EGR,soda can tin and a gasket blocking the EGR.

-MIke

 

[ddavisaf]

Drop a bunch of soapy water all over the area that you think the leak is coming from. Put 25 psi through it. Then look for the bubbles. Your PCV rattles when you take it out right? And it's ran to the Intake Manny correct?

 

[Boost95]

I have done all of that. I dont see bubbles anywhere. And yes the pvc rattles and its installed correctly.

 

[ddavisaf]

Open the oil cap and run the test again listen for air in the head.

Remember hearing the air leak in the exhaust? That would be caused by your valves sticking open.
If it's still happening then try rotating the crank approx. an 1/8th of a turn or exactly 30*. 45* is an 1/8th so just a little less than that. Keep rotating then listening 30* each time until you can't hear the leaking anymore but replace the oil cap first. Then test from the turbo again.

 

[Boost95]

When I have the oil cap off I can hear it alot more thru there. I dont have a socket that big to turn the crank. What else can I do? Why isnt my compression low then? I got 155 across all 4 last time I ran it. Thanks for the help. IM working on the car now, so as soon as you post, i can give it a shot.

 

[ddavisaf]

Okay.... Try this out...

1. Start the pressure test from the licp, if problem fixed it's the turbo seal. If not, go to 2.

2. Unplug the pcv hose from the intake manifold and plug it up and repeat pressure test. If problem fix change the pcv valve.

Boost can enter the crank case in many different ways.

1. Turbo seal ->oil return line -> oil pan
2. Defective pcv valve.
3. The piston rings.
4. Valve seals.

( oldman)

 

[Boost95]

Copying the OLDMAN's post I see Like I said. I tested it from the TB elbow. You can clearly hear the sound when I open the oil cap. I took the PCV valve off and blew thru it to see if it was working properly Is that good enough to see if its working properly? Also the compression is 155 across all four and the car never ever smokes. Only a little black if I rev it hard at idle. And I mean a real small AMT. Thanks for the ehlp tho I appreciate it. What can it be WTF

 

[oldman]

How many posts is that now?

 

[Zenja]

When I have the oil cap off I can hear it alot more thru there. I dont have a socket that big to turn the crank. What else can I do? Why isnt my compression low then? I got 155 across all 4 last time I ran it. Thanks for the help. IM working on the car now, so as soon as you post, i can give it a shot.

Just so you know, you're supposed to turn the crank with a 1/2 inch drive ratchet, not a socket.

 

[steve]

Just so you know, you're supposed to turn the crank with a 1/2 inch drive ratchet, not a socket.

Just so you know, you can use both.

People have been know to crack the corners of the bolt when torquing it using just the 1/2" center but it does make it easy to turn the engine over.

Steve

 

[ddavisaf]

10 posts so far. 10 more to go... and it's like I'm trying to cross the Atlantic ocean in a rowboat....
I'm tempted to come to PA to tear into this car with you, it's much easily to fix things when you're doing it hands on instead of over the internet.

Did you unplug the pcv and repeat the pressure test? Under boost it's supposed to seal shut, under vacuum it should be open.

Did you run the test from the licp? I know I'm skipping around a little, but bear with me

I love copy/paste. Majority of what I know I learned from reading oldman's posts. This young buck still has some tricks up his sleeve though

9 more to go.

 

[renovatio]

I seem to be have the same promblem with mine I have the same cams but have also done a lot of porting work. mine cuts out hard at 5500 rpm. I have the walbro fuel pump
and the safc. The catch 22 with the safc is that if I incress the amount of air the engine thinks its getting to richen the mix to account for more air flow it cuts out sooner. If I try to go the other way The engine cuts out because it is to lean. I think what I need Is bigger injecters. How do I select the right size injectors?

 

[Boost95]

Well im hoping its my PCV. I thought it wasnt suppose to shake. I read in the chilton and it says it should shake around. I guess Ill try that 2morrow with a new one.

 

[Boost95]

Whats going from the LICP going to prove?

 

[ddavisaf]

LICP tests the turbo seals. If you don't get the same sound out of the oil cap on the LICP, your turbo seals are bad. A shot in the dark, but worth a try.

 

[Diplomat]

"I just put hks 264/272 cams in and every once and a while when i boost to 18 or higher i get this horrible cut and just seems like i hit a wall. I have no clue what this is..." - jkrause

You're kidding, right? With as many modifications as you've made, not the least of which is a 6-bolt swap, you're hung up on fuel cut? Alright, not to worry, bro. Many have come before you.

First off, if we refer to fuel cut as what it actually is, MAF overrun, then there would probably be a bit less confusion about the subject. Fuel cut is what happens when the MAF reports to the ECU that it's reading far more airflow than your stock engine was meant to see. Once you hit this magic number, the ECU says,"#%&@ this warranty voiding bull#%&@!", and puts an immediate stop to your fun with an attention grabbing,"NO FUEL FOR YOU!". So don't blame your injectors, fuel pump or your buddy who borrowed the car and brought it back with a full tank of 87 octane. This is a battle with your MAF and ECU.

So we know what the problem is, now what do we do about it? Well, you'll either need an ECU that can be reprogrammed (Socketed EPROM ECU, DSMlink, AEM EMS, etc.) or a piggy-back fuel control device like the SAFC which can push back the point at which you get to experience fuel cut again. The latter choice is one of the less expensive options, but you may not completely eliminate your fuel cut issues by going this route.

This is one of those common problems that's been discussed to death, so you may want to bookmark and check out some of these links and read up.

DSMtuners Forums > Frequently Answered DSM Questions > What is Fuel Cut?

1000 Already Answered Questions

Visual Frequently Answered Questions

There's more, of course, but these are good places to start.

 

[Boost95]

I got a new PCV and it stil hits fuel cut. Whn you say LICP do you mean put it on the j-pipe? I dont see it making any sense putting it on the LICP. That would be the same as putting it on the TB but woudl show a leak at the BOV. Give me all your ideas because I want to blwo it the hell up
Thanks,
MIke

 

[Volume Eight]

boost,

i actually just sat here and read every post, and you never answered Oldman's question of whether or not the turbo had any shaft play? With a 3" DP/exhaust, a 14b could be creeping like crazy, and checking for shaft play would more than likely show signs of this. have you listened near your oilpan? Do you hear the oil bubbling at all?

Just before my 14b went (with a 3"DP/exhaust) i would hit fuel cut like crazy, and the boost levels were very inconsistent and this was off of the BCS.

I know it is a long shot and doesnt really have much to do with your leak near the IM, but you never anwered about the shaft play...

I hope you get it running again soon!

Peace

 

[Boost95]

Thanks for the faith I think I did answe his question, but If I didnt. NO, the turbo has NO SHAFT PLAY at all. And no I did no listen near the Oil Pan. Keep in mind I bought this car from the original owner which was 65 years old when I bought it. He only serviced it at the dealer and probably never saw boost The car does have 173k but its alot of highway miles from him driving to Michigan. I hope ot figure it out soon because I have big plans for the car. I have a nice big FMIC mounted but didnt bother running the pipes. Well, the captain is calling Thanks for helpign my drunk ass out

 

[Boost95]

Alright, we have it narrowed down. Your 20 Post Guarantee, just might work. We know its leaking from the oil cap now. I replaced the PCV and it is still happening. SO theres not much left

 

[steve]

replaced the PCV and it is still happening.

Did you remember to test the new PCV or did you just buy one and put it in?

If you bought one from NAPA/AutoZone/PepBoys it's pretty much guaranteed to leak. If you bought one from the dealer you have a 50/50 chance of it not leaking.

Steve

 

[Boost95]

I just put it in. Only way I know how to test it is to shake it and see if it rattles. It was a FRAM replacement. My stock one still shook btu I replaced it anyway.

 

[steve]

You have to pressure test the PCV. Apply 20+ psi to the side the attaches to the intake manifold (barbed end) and chec that no air leaks out the side that threads into the rocker cover.

Steve

 

[Boost95]

I just tested 3 of them. 2 stock ones and the aftermarket FRAM. All I used was an air gun with a small tip and lined it up. The 2 stock ones leaked alot. The aftermarket one leaked a little bit still. Im going to do the boost leak test later with the PCV elimintated to see if I still have a leak so it can be ruled out.