lifelongpilot

Hey guys, two part question, as this is one of my first posts ever.

I just bought my third 8 and the main issue I found was power loss under wide open throttle or around 6k rpms (I know, we've seen this a billion times) So being a "long-time" member, I searched and searched, replaced and repaired.

Long story short, new coils, wires, plugs, gutted cat, solenoids and valves functioning properly, fuel sock cleaned, I hated the K&N typhoon the guy had in it and immediately bought a stock intake, MAF sensor cleaned, ESS cleaned, NO CEL!)

Car is completely unable to take pedal to the medal from idle or anywhere along the rpm band, and this is in neutral free revving, but it will accelerate smoothly if you do up to around 6000 rpms before the bogging, some backfiring, and even computer cutoffs happen. I've been successful in getting it past this range up to redline but that is really forcing it and I don't want to do that again. Note this is all still free revving and the "misfiring" produces no CEL whatsoever. And every time you apply the gas pedal from idle, there is a momentary drop in rpm.

RX8Soldier

iTrader: (24)

You mention the intake- is it installed properly? Are there any restrictions to the air flow? Clean filter element?
Have you checked the throttle body? Is it functioning?

lifelongpilot

I really didn't think about the throttle body, I should swap in my spare just to see. THe tb does its bit test and you can hear it moving with the gas pedal, don't know if it can get out of wack or not. Intake is installed correctly, even that K&N was, It just really seems more and more like a fuel issue. New pump is on the way.

RX8Soldier

iTrader: (24)

I actually misread your first post. I thought you changed the pump. That would have been my first thing to verify.

hoosier1104

iTrader: (2)

Sounds like your fuel pump is going out to me or a fuel line issue.

wankinit

I've got the same problem. Have had it come and go over the past 4-5 years. It seems to go away when I add Lucas UCL to the gas. The weird thing is that when all that snap crackle pop starts happening my AFRs go down to 11.0 as the power tries to come back the AFRs begin to flicker up to 11.7. That's when it's really making some jam. My engine stumbles when it starts to get rich. I will be changing fuel pump and injectors in the spring and will update my findings. But for now it's "marbles in a can"

wankinit

also I've changed everything as you did. Except look at the fuel pump or injectors, because this happenes when she's rich, I figured look at everything else first. But who knows? I may just learn something new. If you figure it out please let us know we are still trying to debunk this.

lifelongpilot

https://youtu.be/5DGDCCw8hd4http://

Sorry it has taken so long, but here is a video of the car in its current state.

Reminder, this comes after I've done all of the following:

-Gutted Cat
-Spark plugs, lead, coils changed
-All air valves and solenoids cleaned, vacuum checked, and operating
-MAF sensor cleaned
-ESS cleaned
-Throttle body swapped with another
-K&N typhoon intake replaced with stock
-all six fuel injectors swapped with known working ones
-Fuel relays/fuses checked
-OMP operational
-Compression not checked, however, there are no symptoms of low compression (i.e. cold/hot start, misfires with CEL, nothing like my last two rx8s)
-A multitude of 20 brake stomps
-Fuel sock cleaned (wasn't dirty)

I am not really new to the RX8, but this problem is very new to me. Can poor fuel pressure cause such drastic symptoms? Btw, it certainly smells lean to me.

9krpmrx8

iTrader: (46)

Broken link.

lifelongpilot

sorry about that

9krpmrx8

iTrader: (46)

You did all that without ever verifying fuel pressure? And when you gutted the cat was it already falling apart or was it intact? Cat pieces have been known to make to the exhaust and clog there.

lifelongpilot

I was able to get a static fuel pressure reading, but I didn't have the connections necessary to get an inline pressure reading. The fuel pressure was a pretty good 56psi the first time I primed the system, but after a few bleed downs, it never seemed to be able to get over 40psi. I have that pressure tester from harbor freight, not sure how reliable it is though.

The cat had a few pieces but they were trapped between the two elements, it was definitely getting red hot hot after barely going around the block. After gutting the cat I tested the car with the catback removed, same issue, alotttt louder. angry neighbors:/

lifelongpilot

Now I believe I'm truly stuck. NEW fuel pump finally installed and the car is running exactly the same way.

1) I noticed that the fuel running back out of the line that goes into the pump whenever I disconnect it has a brownish color to it, definitely not the same color as what goes in. Suspecting I had a rusty line, I used a length of fuel hose to connect from the fuel pump directly to the fuel rail inlet.

2) My only other thoughts on what causes this the car to idle fine but run horribly is a computer that's out of whack somehow, or the fuel resistor? Maybe bad fuel speed circuit wiring (relay tested good). If the speed circuit is bad, would that cause these symptoms? (See video)

I read that APV failures should almost always throw a CEL. Is it possible for it to fail without? That's the only other thing I haven't attempted to remove for cleaning or test.

The video I posted is still valid for how the car acts now. Any help or insight is appreciated!