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fuel cutoff at full boost

1K views 10 replies 6 participants last post by  SPATL 
#1 ·
is there an easy fix for this? what an experience!
 
#3 ·
A friend's car (that I'm thinking of buying, actually) has this same problem. He said that an indie mechanic tried replacing the BPC with another from the junkyard, and the car still had the same problem. Is there any other cause for hitting fuel cut, or did he just happen to get another bad BPC from the junkyard?

Thanks!
 
#7 ·
ok. i think i know what has transpired. the former owner had installed and mbc, bov, sport exhaust and some other mods like k&n AF and maybe a modifed intake lableled hks? anyway, the ecu is stock so he disconnected the vac hose to the Map sensor to trick the ecu so that he did not get fuel cut at 15psi, in fact i was pulling 20-22psi with no problem. however this caused the car to run poorly with hestitations and stuttering. hence my visit to dealer where they quickly diagnosed a vac leak to map sensor then charged me $200 to replace a $5 vac hose. now of course the map sensor is back online so that explains why the car runs better but i now have fuel cut at 15psi. so, where do i start now that i think i know the history? i thought the answer was to order a tuned ecu from nordic but when i called the guy said i had to remove my mbc and go back to stock using apc, which i dont want to do. any thoughts on an easy fix to relieve fuel cut? a guy at kcsaab said you can put a volt clmap on the MAP so it doesnt go over 3.45volts which triggers fuel cut?
 
#8 ·
Take the heat shield off and grab ahold of the WGA arm and pul it towards the driver side of the car. You shold be able to do this with some resistance of the spring load in the WGA. It should move. If it does ot move, it could be stuck shut. You would need o be careful with tapping it open so not to damage the WG or the arm of the WG that attaches to the WGA arm. This would be the test to make sure the WG flapper can open though.



Or if you have compressed air, you can detact the hose going to the WGA and send about 8psi through the hose and increase it by 1 psi until the WGA opes the WG. This would give you a measure as to ho much force it takes to crack the WGA open.
 
#9 ·
SPATL said:
Take the heat shield off and grab ahold of the WGA arm and pul it towards the driver side of the car. You shold be able to do this with some resistance of the spring load in the WGA. It should move. If it does ot move, it could be stuck shut. You would need o be careful with tapping it open so not to damage the WG or the arm of the WG that attaches to the WGA arm. This would be the test to make sure the WG flapper can open though.



Or if you have compressed air, you can detact the hose going to the WGA and send about 8psi through the hose and increase it by 1 psi until the WGA opes the WG. This would give you a measure as to ho much force it takes to crack the WGA open.
I can move the WGA but it is quite tough by hand, I hand my mechanic look at it not to long ago, and he said the BPCV funtion normally with compressed air into the vaccum line(not sure what PSI),. I also notice when i hit fuel cut off, i hear a worbaling air sound (poss bad bpv) ? I ahve ordered a SMBC from you, hopefully this will fix it. Thanks for the reply
 
#10 · (Edited)
The SMBC will probably not solve your fuel cut problem and potentially exacerbate the issue. Th WGA arm on your car is harder to move than those on a Garret T25 turbo. The Mitsubishi TD04 wga is stiffer than the T25 acuator so it doesn't surprise me that this is the case.

Why you're hitting a fuel cut and the car is not throwing a CEL is beyond me.

Test this: Turn your key to the on position before starting the car and check to see if te Check engine light comes on. If it doesn't, the light may be burned out. If it does come on, and you hit fuel cuts, that would be wierd. The T7 engine is a fickle beast and typically throws a CEL more often than the older T5's do.

Sometimes a dying DIC can feel like a fuel cut but with that your CEL would come on.

Check the CE light first and report back.
 
#11 · (Edited)
jimzigg said:
ok. i think i know what has transpired. the former owner had installed and mbc, bov, sport exhaust and some other mods like k&n AF and maybe a modifed intake lableled hks? anyway, the ecu is stock so he disconnected the vac hose to the Map sensor to trick the ecu so that he did not get fuel cut at 15psi, in fact i was pulling 20-22psi with no problem. however this caused the car to run poorly with hestitations and stuttering.
Yeah because you're car was fueling for less than 20-22psi of air and was probably running wicked lean:eek:

jimzigg said:
hence my visit to dealer where they quickly diagnosed a vac leak to map sensor then charged me $200 to replace a $5 vac hose. now of course the map sensor is back online so that explains why the car runs better but i now have fuel cut at 15psi. so, where do i start now that i think i know the history?
by checking the integrity of your pistons and compression in each cylindar.


jimzigg said:
i thought the answer was to order a tuned ecu from nordic but when i called the guy said i had to remove my mbc and go back to stock using apc, which i dont want to do. any thoughts on an easy fix to relieve fuel cut?
Yes, this is true. If you are going to go with a modified ECU, you must remove the MBC and let the stock BPC control the boost. The modified ECU WILL raise the fuel cut limit but will properly fuel for that. The stock ecu does not know how to fuel for anything over 17 psi or so.

jimzigg said:
a guy at kcsaab said you can put a volt clmap on the MAP so it doesnt go over 3.45volts which triggers fuel cut?
Yes, this is called a MAP hack. There are a few who have done this and here are two ways of doing it. A volt clamp is one way, a resistor in line to the gray wire o the MAP is another way, BUT this is getting out of the area of safe mods. It has been done to use a low resistence resistor, say 10-20ohms but your stock boost gauge will not show the increase in boosy as it will continue to show normal boost but your boost is actually higher. A mechanical gauge taking pressure off the manifold will show the increase though. This is a black art that need to be done carefully as you can damage your engine badly if not accurately monitored with the right gauges. Again, a black art. Proceed with caution. Also note, this can only be done on a T5 engine. Don't even think of doing it on a T7.
 
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