Lately my fuel cut off seems to be creeping lower and lower. This morning it was cutting at 6 psi. I have no idea even where to start here, any help is greatly appreciated.

Here are the details:
Fuel cut hits sooner when colder, it was about 34 degrees this morning (in SoCal! what's up with that)

Happens more when going up hill (greater load on engine)

97 850 T-5

Lots of miles

Did a full stage 0 about 2 years ago and replaced plugs since then

MBC was set to about 14 psi, but have since backed off

Running 91 octane gas

Recently changed fuel filter (but was happening before then)

Any Ideas? more info required?
Thanks

 

accidental double post how do I delete this?

 

vacuum leak, check all vacuum lines from the vac tree to the bcs, to the turbo

boost leak, check all intercooler hoses top and bottom.

 

Are you sure it is fuel cut and not misfiring?

 

Thanks for the input. I'll check the vacuum and intercooler lines. Pretty sure its not a missfire. This isn't roughness but full on cut of all power

 

OK very strange. I would check the intercooler hoses like stated above.

 

Every once in a while my oem ignition coil would go bad and cause total power loss under full throttle, happened in either 1st or 2nd gears but since I got a msd unit, all is smooth.

 

How many miles do you have on the plugs and are they copper or an upgrade ??

 

I've got the msd coil already,

For the plugs I'm having a tough time remembering right now, but from what I recall I got copper, the platinum and iridium don't work as well right? In any case could the plugs cause the fuel cut? Missfire I get it. But the fuel cut comes in when your computer detects too much boost pressure. If it detects knock it changes the timing which results in loss of power but not fuel cut. Do I understand this correctly?

 

I want to clarify a couple of points. The symptom I'm experiencing here is exactly the same as when I was setting up my MBC. When all was good the boost gauge would swing up and if it got to around 15 PSI the fuel would cut completely, all power stops for a moment.

On cold mornings the cut would come in earlier at maybe 11 PSI.

Recently the fuel cut has been coming in sooner at 9 PSI or even 6 PSI.

I thought it could be that I got a leak in the hose to my boost gauge and the reading was off, but the power is down too. I'm not getting the acceleration like I was at higher boost.

I've checked the vacuum lines and they seem fine. I need to check the intercooler hoses, which is a little bit more involved.

Perhaps it would be helpful if I better understood what triggers the fuel cut. What is the computer monitoring and why it cuts fuel in response. With this information I can follow a more systematic diagnostic process.

Thanks again for your help.

 

i have a similar problem, in the summer the car seems fine (even at 12PSI) but in the winter it cuts randomly anything more than stock..
Have not solved it yet.
Also i used to get random misfires but never any codes. ( since i changed the plugs hasnt happened since OEM) and i think i still get a shudder on the highway when in boost.

 

You are correct about the knock sensor retarding timing. How many miles do you have on the plugs ??

With the MSD coil you are able to supply a hotter spark. I run AC Delco Platinum and have had no problem. I have had conflicting input on spark plugs, some stay to stick with copper only in a high performance turbo and change them often and others who run platinum or iridium and wouldn't think of screwing in a standard copper plug. I like the better plug for less maintenance.

 

Over the weekend I pulled off the MBC and the fuel cut is completely gone. Am I correct in assuming that if there were any leaks in the vacuum lines or intercooler hoses that the fuel cut problem would persist?

If that is the case any suggestions/theories about why I have seen the fuel cut issue moving lower?

 

x2, but my stock boost is 6psi. when i take it off it works great.

cheap MBC? mine cost 20$