stevensettle4321

Hey guys owned my rx8 for a while now. First off weed out the obvious answers I'll probably get. Coils are good, all spark plugs are getting spark brand new fuel pump, new spark plug wires, catalytic converter is gutted. And the engine is freshly rebuilt but not even 5 miles on it. Problem was there before rebuild. And still there after. But I can reach high rpms if I go half throttle. But as soon I go full throttle or put it to the floor it boggs down. Any help would be appreciated.

Jedi54

iTrader: (7)

possibly fuel related?
have you checked fuel pressure / pump?

stevensettle4321

I thought it might be fuel. But like a said new fuel pump. And I can still reach redline just not a full throttle

Jedi54

iTrader: (7)

missed the part about the fuel pump, my bad.
how old are your coils? I know you said they're good but have you tested them?

We need to just eliminate possibilities: It's either fuel, spark, air, or tuning. (we'll get to that last one later)

Is the MAF sensor clean?
stock intake? have you checked the mesh screens to make sure they're still there and straight? Those damn things bend and get sideways.
no CEL's? Nothing flashing when you go full throttle? Any pending codes?

stevensettle4321

Probably not over 6 months but I took out one plug at a time, and turned it over every plug sparked. Maf sensor is cleaned. And your talking about the mesh in the intake? Bit yes still stock airborne and intake. And no, no CEL'S and it use to before my rebuild but nothing now.

Reoze

Do you have an ODB scanner? I'd be curious to see what your MAF, AFR, and throttle position look like while this is happening.

Have you checked the SSV and VDI? These would not have been touched with a rebuild and are opened primarily based on load.

stevensettle4321

I do have a code scanner. And I've tried to check that but couldn't figure out how. And what's the SSV and VDI? Be glad to check.

Reoze

The SSV and VDI are valves on the intake manifold that are selectively opened based on load. I think the technical explanation is that they modify the volumetric efficiency of the engine. If they are stuck closed, then I believe you will end up running extremely rich.

stevensettle4321

And how would I go about checking to see if these are stuck closed? Or if the are opening them back up?

Reoze

This is a VERY common problem with these cars. There's plenty of posts, and videos floating around detailing how to check, and clean the SSV, VDI, and related solenoids.

The easiest way to see if they are stuck is to have someone rev the engine up with the hood open. The SSV and VDI are on the left side of the upper intake manifold and you can see the solenoids opening and closing. Generally the SSV is an issue long before the VDI ever becomes a problem. They have an issue with carbon build up, an solenoid failure.

VDI -
SSV might be a little harder to spot with the air pump in place.


Now with all of that said, I'm not too confident this is actually your issue. You said you replaced the fuel pump, was it with an aftermarket, or OEM pump? Are you sure everything was installed correctly?

stevensettle4321

Okay I messed with the VDI when I was putting everything back together and I could manually open and close it. But if the solenoid is bad guess it still wouldn't open it. I'm going to check here in about 2 hours and see. Thanks for help

stevensettle4321

Okay checked VDI AND SSV neither one of them opened at 4 1/2 and 6k do you know at what rpm the should open or move at? I tried to move both by hand while the car was running and nothing.

stevensettle4321

And on the fuel pump it was one from advance auto parts. And yeaa took pictures before I took it out and put it back in the same way. And the exact same problem was still there.

Reoze

I don't think there's a specific point at all. Like I was saying a lot of it depends on load. But those are the general areas they'd open under normal circumstances.

I'd find it a little hard to believe that neither of them are opening without any CEL's. The SSV has a switch attached to it to confirm that it is in fact open. The switch can go bad, but a CEL usually accompanies that too.

Personally I'd be looking at the fuel pump. It sounds like it's a starvation issue as Jedi was saying. Does autozone actually sell a pump that fits in our car properly? Or did you have to modify it?

stevensettle4321

I'm going to check to make sure I have the sensors in the right order on the intake. But yea advance had one, perfect fit looked just like the other one. And I want to do a fuel pressure test just to make sure but the rx8 doesn't have a port for that. And this time it did throw a cylinder one miss fire light. And one for secondary air pump but mine has been bad for awhile.

Reoze

Secondary air pump is purely emissions. There's a whole thread on misfires, though be prepared to hear that it's your plugs/coils.

Are you 100% sure that all of the internal lines were connected to the fuel pump correctly?