marc1130

iTrader: (20)

The RPM needle and engine struggles at about 4800 RPM and above, feels like its misfiring. 160k miles on the original vented opti. I think i'm gonna replace it with a new gmhp unit but before I do that is there any other cause?

idformula

My first thought is check the fuel pressure, fp should be around 43lbs, and btw good on wanting to replace it with an ac delco/delphi unit.

marc1130

iTrader: (20)

Ill check my fuel pressure and regulator vacuum line, I'm thinking it may be a fuel problem because it sometimes starts up and dies immediately in the morning

WS Sick

Makes sure the fuel pressure is there all the way up not just at idle.

SS RRR

iTrader: (2)

Take opti off, take cap off to ensure rotor screws are not backing/backed out.

I had the same thing a few days ago after 5000rpm and discovered this:

marc1130

iTrader: (20)

Looks pretty clean for an optispark how many miles? I think if I go through the effort of tearing it down, its going to get a new one. Its unfortunate that the screws backed off, heard of using locktite to fix it. Although I took it to redline like 6 times consecutively and its doing it less, but i'm not sure whats going on.

SS RRR

iTrader: (2)

Opti is about four years old and has about 5 to 7K miles on it and has been taken to 7200rpm on numerous occasions. I too was surprised at how clean it was when the cap was pulled.

nitrous2fast

iTrader: (2)

Have you done a tune up like plugs and wires? That would be the first thing. Then, if it still acts up, replace the opti.

marc1130

iTrader: (20)

UPDATE: The problem was the fuel pump I was losing 10psi at WOT near redline. I just finished the trap door modification. I put a Walbro Fuel Pump in (255LPH) from TRE Performance only $99. The harness was plug and play. The pump fit perfectly in the LT1 fuel pump bucket with the provided sock. I bought a 10" flex hose from autoperformanceengineering along with the foam that goes around the pump body to prevent rattling. I zip tied the bucket lid with nylon zip ties instead of glueing it. Fuel pressure stays at a constant 43 psi at WOT all the way to redline, no hesitation or misfires. The car runs like new and has a general increase in power across the board. I am very satisfied with the repair, and glad it wasn't the optispark.