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

 

[crxp-o-s4now]

just boost contoller,k and n filter, and gauge. i had it running 15 before but was told the computer was faulty and needed to change it to rid the engine lights(because we replaced what the codes said and they still didnt go away) so we put a new ecu in..then after inspection, put the old one back in no engine light dont know what is wrong with my car!@!!!

 

[crankbender]

just boost contoller,k and n filter, and gauge. i had it running 15 before but was told the computer was faulty and needed to change it to rid the engine lights(because we replaced what the codes said and they still didnt go away) so we put a new ecu in..then after inspection, put the old one back in no engine light dont know what is wrong with my car!@!!!

First off read on what causes fuel cut.

http://www.dsmtuners.com/forums/showthread.php?t=186971



IMHO you need to find out why you are flowin too much air. This could be that 15 psi is too much with your setup, a boost leak, etc. Read that link first though .

 

[crxp-o-s4now]

im guessing it has to be a boost leak or something..its so weird because when i first bought it, it ran fine..then i had the tps changed, barometric pressure sensor change and some other gas sensor changed and it STILL didnt clear the CEL. So some "Kustom" mechanic said i had to get a new ecu..so i get the new ecu and the CEL's are gone!! phew..then this problem of fuel cut or whatever starts. so we throw in the old ecu thinking maybe it was broken or chipped to eliminate fuel cut etc..amazing how theres no CEL'S on the old computer..aka the one that i was told needed to be replaced!! dam him! so i believe there is a boost leak under the exhaust manifold..CANT FIND IT!! any suggestions on how to find it or where to start looking. And could it be anything else besides fuel cut or a boost leak? i need to fix this a.s.a.p

edit-it seems as if i hook up a hose from my wastegate directly to my intake pipe via that nipple, it runs stock ish boost fine.well around 7psi. and then when the boost controller is teed into that line, no matter what i turn it up or down to, it still hits that cut.

 

[doug]

There's lots of threads on building a boost leak tester and performing the test. Just make the tester, pressurize the system, and the leaks will probably be evident. If not, use a spray bottle with some soapy water in it to spray on all the connectors, nipples, etc. and the leaks will bubble.

 

[crxp-o-s4now]

There's lots of threads on building a boost leak tester and performing the test. Just make the tester, pressurize the system, and the leaks will probably be evident. If not, use a spray bottle with some soapy water in it to spray on all the connectors, nipples, etc. and the leaks will bubble.

thanks man..ive made the boost leak tester a few months ago to test for leaks which is how i know that it is inder the manifold somwhere. i ll test it again tomorrow morning..

 

[oldman]

thanks man..ive made the boost leak tester a few months ago to test for leaks which is how i know that it is inder the manifold somwhere. i ll test it again tomorrow morning..

there is a boost leak under the exhaust manifold

If this is not a typo and you hear leaks around the exhaust manifold during a pressure test, check the EGR valve and make sure none of the cylinders are in valve overlap position.

 

[crxp-o-s4now]

ok i ll find the EGR on that visual 1g diagram when i get home from work..also how do i know if im in the valve overlap position just so i know what im doing and dont mess anything up.

 

[crxp-o-s4now]

thanks for the help wiseman!

 

[oldman]

also how do i know if im in the valve overlap position just so i know what im doing and dont mess anything up.

Just bring the engine to about 30 degrees after #1 TDC. Valve overlap happens at the end of any exhaust stroke when the exhaust valves are about to close and intake valves are beginning to open. Focus on the EGR for now, if problem persists then worry about the valve positions.

 

[crxp-o-s4now]

Just bring the engine to about 30 degrees after #1 TDC. Valve overlap happens at the end of any exhaust stroke when the exhaust valves are about to close and intake valves are beginning to open. Focus on the EGR for now, if problem persists then worry about the valve positions.

thanks doode!

 

[oldman]

You're welcome.

 

[moparmadd]

Ok so the title pretty much summed it up but i will throw in some more detail. i do have an aftermarket boost gauge and it reads a steady 11-12 psi at WOT. but the problem is right around 5500-6000 rpm the engine feels like it hit fuel cut. feels JUST like it with the violent lunging and what not. I had denso iridiums in and today i replaced them with some NGK's just to make sure it was my plugs. cleaned out the throttle body (yes i removed the plastic sensors beforehand). recharged my K&N filter since it kinda got soaked in coolant a few months back (split a coolant hose going to throttle body... or somewhere in that general area). A few weeks ago i borrowed a friends plug wires (ngk's i think) and still have them on and they didnt help. any ideas PLEASE LET ME KNOW!!! Im tired of civics passin me by cause my engine feels like quiting at 5500.

PLEASE HELP!

 

[oldman]

Boost leak test.

 

[Boost95]

Now that I got a new computer and I can hotsync again. What should I log to help you guys better understand whats happening? Let me know and ill go make a log.
Thanks,
Mike

 

[crxp-o-s4now]

ok turns out the hoses were different on a friends setup so we setup my mbc hoses liek his and voilaa!! however i still have a boost leak and its not my EGR. sounds closer to my turbo..ALOT closer.

 

[oldman]

ok turns out the hoses were different on a friends setup so we setup my mbc hoses liek his and voilaa!! however i still have a boost leak and its not my EGR. sounds closer to my turbo..ALOT closer.

1. Spray soapy water around the compressor cover area.

2. Open the oil cap and take a listen during the leak test.

 

[crxp-o-s4now]

off to work will do tomorrow!!

 

[DSM90AWD]

Now that I got a new computer and I can hotsync again. What should I log to help you guys better understand whats happening?

Bruce pulled me away from American Choppers to see if I could help out.

Log1: O2 Volts, Knock Sum, RPM, Timing, TPS
Log2: Low Trim, Mid Trim, High Trim (few seconds of log as these vaules won't change much)

Other than the log couple thoughts of my own (sorry of answered in prior 7 pgs )
- NGK Plugs gapped properly?
- Have you checked your plug wires for cracking/arching?
- Timing belt properly installed?
- Base timing set correctly?
- Swapped out FPR?
- CAS installed 180deg out?

Is there anything that happened immediately prior to this problem that could be the cause (e.g. engine work, new part, cheap gas) ?

 

[steve]

Log1: O2 Volts, Knock Sum, RPM, Timing, TPS

Need IPW to tell if the problem is really fuel cut. MAF HZ would also be useful.

Steve

 

[oldman]

Bruce pulled me away from American Choppers to see if I could help out.

Oh shit, it's on.

 

[Boost95]

Yea, I was watching AC up until the point they tried to fire it up. Before going any further. I found another major problem. I had some extra time on my hands 2day so I did another test at my TB inlet. I was excited to hear that my PSI from the TB elbow was alright to keep me from hitting fuel cut. But since I was still hitting fuel cut I figured it was a good possibility I had a leak from the Turbo-TB elbow. I did the test and there was a loud hissing near the turbo and would not build much over 10 psi. I got a small piece of Vacuum tube and poked around near the turbo. Right on the rear side of the inlet was leaking out real bad. So I'm guessing there is some type of seal in there that is shot having 173k! I guess this is a good reason I barley hear my turbo spool up and I hear the turbo spool down so much on DeCel. I just want to make sure on something, with it holding the boost for 40 seconds from 20-0 @ the TB elbow.. That is long enough that I would not hit fuel cut? I'm trying to figure this out to see wheather I should take care of the Turbo or where to go from here. Thanks alot for taking some time from American Chopper to help me out. Its on all night 2nite

Thanks
-Mike

 

[Boost95]

Is there anything that happened immediately prior to this problem that could be the cause (e.g. engine work, new part, cheap gas) ?

Sorry, I forgot to reply. No, I bought the car bone stock and it would run 10psi w/o hitting fuel cut. Since I put the exhaust on it creeps to 12-13 psi and hits fuel cut.

 

[gnes100]

is your boost controller on the right way? mine leaked air out of that little hole in the nipple when i had it on backwards === but it would boost up waay high and start popping!! Have you changed your fuel filter out lately ???

 

[oldman]

Yea, I was watching AC up until the point they tried to fire it up. Before going any further. I found another major problem. I had some extra time on my hands 2day so I did another test at my TB inlet. I was excited to hear that my PSI from the TB elbow was alright to keep me from hitting fuel cut. But since I was still hitting fuel cut I figured it was a good possibility I had a leak from the Turbo-TB elbow. I did the test and there was a loud hissing near the turbo and would not build much over 10 psi. I got a small piece of Vacuum tube and poked around near the turbo. Right on the rear side of the inlet was leaking out real bad. So I'm guessing there is some type of seal in there that is shot having 173k! I guess this is a good reason I barley hear my turbo spool up and I hear the turbo spool down so much on DeCel. I just want to make sure on something, with it holding the boost for 40 seconds from 20-0 @ the TB elbow.. That is long enough that I would not hit fuel cut? I'm trying to figure this out to see wheather I should take care of the Turbo or where to go from here. Thanks alot for taking some time from American Chopper to help me out. Its on all night 2nite

Thanks
-Mike

So you're saying you never went back to test from the turbo inlet after the TB elbow? If you're only able to build 10psi at the turbo inlet you need to fixed all leaks until you're able to build 20psi just like the TB elbow. Spray soapy water around that area and pin point the leak. Also open the oil cap and listen for leaks, it could the seal as well.

 

[gnes100]

have you changed out your fuel filter lately ?