I am completely at a loss here if anyone has ever experienced this problem. I only experience the shutter past 6000 rpms- redline. It seems more like a fuel cutout problem. I have replaced all four injectors, spark plugs, wires, fuel filter, most vacuum hoses, all cats with a magnaflow direct fit (currently leaking by the way), borla catback, and k&n performance intake. I have a perfect idle of 750 and the car starts everytime with no problems. I have also checked the throttle position sensor and achive perfect readings. Anyone think this could be a problem with the 5th and 6th port actuators? Any help would be greatly appreciated.

 

I have since repaired my exhaust leak with no difference. I was able to check both the 5th and 6th actuators and they are funtioning. I would consider this shutter more of a hickup. It seems like an ignition problem. I also swapped out the ignition coils one by one with no effect. I was also suspecting a problem with the choke for the cold start assist that connects to the throttle plates so I used a ziptie on the choke to hold the plates open. This also made no difference. I will be doing a compression check in the next couple of days. Anyone have any other ideas?

 

Power drops / studders in the 5-6000 RPM range are generally issues with injector wiring. There are a few example I can think of where someone has had a similar issue, and the problem turned out to be a loose injector clip, broken wire, etc... If you can make it to redline only giving it partial throttle, it's a pretty good bet that you're experiencing a lean hesitation at WOT.

 

Thank you for the reply. I had a chance last week to check all four injector wiring to find no problems. I reseated all four injector connectors as well with no resolution. I think my problem is that these injectors flow 10% more than oem which is causing the lean problem I am describing. The injectors I installed are venom HP627-091. I replaced them originally due to at least one leaking causing flooding problems. I do still have the original injectors so I will send them out to witchhunter for rebuilds and flow tests.

 

I guess you didn't read about the Venom Injectors..
They are crap amongst the Rotary crowd.

 

10% more fuel would cause a rich condition, which could cause a studder at the secondary injectors transition (3800 RPM, 0 manifold pressure), but otherwise go mostly unnoticed. But adding fuel to an otherwise stock NA will decrease power. The fuel maps are rich enough from the factory.

As mentioned, Venom has a less-than-stellar reputation. A flow test may reveal that they're flowing much less than they claim. But serviced OEM injectors would be a better bet anyhow.