Problem under boost, need help plz!

[1991gs-t]

Hey guys, I've been having this problem for the longest time and i really really would like to get it resolved. Basically what happens is that the car will sputer at WOT under higher boost levels (anyhitng over .5barr). The problem is that the car is inconsistant. Heres a typical scenario of what happens: I'll go ahead and put in some new plugs and the car will run fine for ~ 3 to 4 good pulls, then this problem happens again. Ive done this maybe 3 times...same thing everytime. Once it does sputter , it will always do it on those plugs. The plugs dont look too bad, maybe a little blackish from running a little rich, but nothing crazy. Today, i did something different. I changed my coil, and immediatly the car feels 100x times better and doesnt sputter anymore. After about a bunch drives of pushing the car with no probs many times...the same thing happens again! I Was almost certain that the coil was the problem becuase i pressure tested the system maybe 20 times in the past few months and have gotten almost all of the leaks sorted out. Im stuck. The bottom line is this: the car will not run fine unless I keep changing plugs and even then it only last for a couple minutes. Changing the coil made a nice improvement but the end result was still teh same. There are no major boost leaks, and the coil that is in now should be ok still. Car drives perfectly normal unless i build boost. Any advise you guys could shoot my way would be totally appreciated. Here are a list of my mods just to give you an Idea:

2.5" exhaust, Supra sidemount, 2.5" UIP & LIP, K&N filter,walbro 255HP, AFC(all zero'd out), boost and egt guage, boost controller, semibuilt motor and semibuilt tranny.

thanks a bunch guys

 

[Lordpaxin]

ok, .5 bar is high boost?
thats like 7.35 psi,

do this.
the wire on your AFC that connects to the Injector duty cycle wire,
disconnect this.

go for a drive.


my car was doing the exact same thing, and i had an avc r installed and monitoring injectors.

when in guage mode, i could see the reading on the duty cycle for injectors go ape shit when sputtering uder boost.

unhooked wire, and its perfect.

see if your reading goes ape shit during boost sputter, first.

 

[1991gs-t]

the duty cycle looked ok to me......


It kinda feels like a major boost leak.....but its not.

 

[92awddsm]

Get an afpr. The 255 pump is probably over running the stock fpr. Also, double check the timing belt and make sure all the marks line up. Could be 1 tooth off on one of the cams.

 

[1991gs-t]

Get an afpr. The 255 pump is probably over running the stock fpr. Also, double check the timing belt and make sure all the marks line up. Could be 1 tooth off on one of the cams.

Timing belt is fine. An afpr is also on my list, but I seriously doubt it would be the cause of this. Many people run the 255 without an afpr. The main problem would be at idle, which I don't have so I wasnt too worried about it.

 

[1991gs-t]

no one else??