Is it fuel cut or is it detecting knock?

[fiyota]

I'm having a problem with what I think is fuel cut. I'm running about 8-9lbs of boost and it seems like it's hitting fuel cut. I have a K&N intake, hardpipe w/ bov instead of accordian pipe, with the stock turbo elbow & dp to a 3" exhaust (no cats or resonators). I've checked the ic piping for leaks and even removed the intercooler (wich has been patched up, so I thought an air leak will cause the turbo to have to pull more air in than needed causing me to hit fuel cut).. even with my patchy intercooler removed I'm stilling having the same issue.

at full boost (most commonly in 3rd and 4th gear) the ecu seems to stop the fuel cause the car to stop a bit, then the check engine light comes on for a few seconds then goes away. Is this fuel cut or is it the ecu detecting knock and pulling the timing on me for a second?

Could it be that my intake and exhaust are flowing so well that I'm just hitting fuel cut (wich is supposedly around 11-14psi)? Any help would be great here!

 

[isnms]

Your engine light came on...check your codes
http://www.cygnusx1.net/Supra/TechTips/engine_error_codes.aspx

edit: cool pic in your sig :bigthumb:

 

[jetjock]

Knock does not result in turning on of the MIL, while knock system fault will keep it on even if it's a momentary failure. Take his advice and check your codes.

 

[fiyota]

Ok so there will still be codes even if the light came on for a few seconds?

This sounds like fuel cut tho right?

 

[88supraFAST1]

it doesnt seem like fuel cut your only running 8-9psi.

 

[TurboStreetCar]

big boost leak and 8-9 psi equals fuel cut. i hit fuel cut at about 10 psi with some small boost leaks.

 

[fiyota]

Yup code 34... now if I fixed the leak... and didn't clear the codes, would I still hit fuel cut? Because I don't have any other leaks in the system that I know of, unless my bov is leaking...

 

[88supraFAST1]

you always clear your ecu after you try and fix something.

 

[jetjock]

Yes, the computer stores a code even if the light goes out. On the other hand codes can be stored without turning the light on at all. It's why you should occasionally check for codes, say at every oil change. To make matters worse a few codes are not stored in memory. Confused? You just have to learn how the system works but in general don't confuse the light with codes.

As 88 points out always erase codes after making a repair attempt. You don't want old ones left behind. As for yours, what nosechunks said. You likely have a leak(s) that only opens under pressure.

 

[fiyota]

hmm... I'm going to try making one of those boost leak testers and test the system for leaks by pressurising it (and block it off at the t body).. I know this will only test the intake/ic side of it but it will still eliminate those parts as an option. I'm also going to find a way to get my stock recirc valve hooked up to remove the bov as a possible suspect. Then I guess I'll check for vaccum leaks with my mityvac...

Anything else I should do to track down any leaks that would cause fuel cut at only 8psi?