RX-8 40th Anniversary

Hey hope everyone has had a swell year so far. Happy late easter!

I tried looking around but the problem I stumbled across an hour ago with my RX8 I couldn't find a solid response, so forgive me if I ask about a problem that has a solution already.

I took my RX8 out just for a nice drive and went down a straight road. I was accelerating just fine until about the 4-7k RPM mark, but this was done with more than 60% throttle.
The vehicle likes to bog/choke/struggle under "hard" acceleration in the 4-7k range. I can rev the engine just fine in the powerband, and accelerate normally just fine til about 4th gear. Then it just struggles to accelerate.
Again I apologize for help on a problem that might have a solution but I am truly lost here.

No cat, replaced the engine about two years ago this may and has ran flawlessly fine since then.

The vehicle's engine is just sitting at about 6k miles and was replaced last year, so I don't drive it a whole lot. Thanks for taking time to read this for those that can.

BigCajun

iTrader: (1)

I've noticed this at about 7k as well, but it seems like it's when I'm driving it agressively.
I haven't done it a whole lot, but I did notice it.
It doesn't always plateau there, I have redlined it.

MincVinyl

Was the car driving perfectly normally and then this happened? Or did this start after some maintenance?

I would point towards an issue with the 3 vac solenoids, or the wiring, or the vac lines, or the SSV, or the VDI. The SSV and VDI are the two valves on the LIM and they can get gummed up by carbon. If the solenoids are bad you can also get strange power struggles in higher rpm bands.

Otherwise it could also be the fuel pump is beginning to let go and struggling at higher rpm.

Aftermarket intake? Drive through any heavy rain? MAF not reading right and bogging? Happens with my AEM intake if I hit 5+k rpm in heavy rain.
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Or see if your throttle body has any issues. Can you full throttle no problem at low rpm? Doesnt sound like it, but easy to check

What ignition coils and sparkplugs are you running?

TeamRX8

iTrader: (25)

SSV and VDI are also vacuum operated; bad check valve or leak will impact them too, VDI operation is above 7000 rpm though … but if the SSV doesn’t open that’s going to limit power from ~4000 rpm and higher
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RX-8 40th Anniversary

Yup, driving perfectly fine then all a sudden boom..
The car isnt heavily modified at all, the engine has about 6k miles on it with an aftermarket kit for the fans to kick on, and that's really about it other than a cat delete. Oh and LS coils as well.
Ignition coils are the LS ones- Kyle put them back and I will more than likely just keep buying LS coils strangely.. Spark plugs are also relatively new, they are the NGK spark plugs.

I have narrowed it down to the fuel pump- I put about 30$ of gas to 3/4ths of a tank and it went away. Started to get below a quarter and it slowly occurred again, so I'm just gonna go ahead and replace the pump as it's only two years old from delphi. I already bought one and am just waiting for the weather to get dry again so I can take it out one last time to use the gas, then change the pump.

However in the mean time I will definitely check the VDI and SSV.

Edit : The problem pretty much occurs as soon as the vehicle is completely warmed up as well.

And thank you all for responding- I am really bad at checking stuff nowadays but I really appreciate everyones input and advice.

TeamRX8

iTrader: (25)

yes, classic fuel pump symptoms …
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RX-8 40th Anniversary

Turned out to be the fuel pump. No problems whatsoever and hasn't had any hiccups since then.
BigCajun, If what you're encountering is a problem then I hope it gets resolved. I know mine went out when I had my engine replaced.
MincVinyl, Thank you for your input and the extra things to look for as well. I really do appreciate your advice and wisdom.
TeamRX8, Thank you as well for your input and your advice as well, If the problem occurs again I will look into what you have said that could potentially be the problem.

I do apologize for this thread as it seems to be an occurrence with these vehicles, as this thread was not necessary.

Thanks to everyone!!

gwilliams6

Yes I am not surprised it was the fuel pump.

Info for all of us:

RX8 Engine Power Loss

• chokes as revs increase
  • O2 sensor failure (too rich)
  • MAF failure
  • MAF disconnected
  • e-shaft sensor fouled
  • accessory belt fraying
• high end power loss (hard fuel cut)
  • Rev limit reached
• high end power loss (jerky and stumbling)
  • Ignition failure
  • fuel pressure loss
  • e-shaft sensor fouled
• high end power loss (smooth)
  • Catalytic converter clog
  • air filter clog
• low end power loss (smooth)
  • Engine compression loss
• low end power loss (stumbles)
  • Ignition failure
  • front O2 sensor failure
• revs slowly but smoothly
  • O2 sensor failure (too lean)
  • catalytic converter clog
  • air filter clog
• sudden power drop at a specific rpm
  • Intake valving actuation problem
• trouble getting to redline
  • Ignition failure
  • front O2 sensor failure
  • catalytic converter clog
  • air filter clog
  • e-shaft sensor fouled
  • fuel pressure loss
  • MAF failure

Folks, ANY still original Series One fuel pump needs to be replaced after this many years and many miles/kilometers. They were grossly under-engineered IMHO. I recommend upgrading to a Series Two fuel pump, far superior, and Mazda knew they had to change that for the Series Two and did. . I and many RX8 owners have had bad failures with the Series One pumps. They fail under high load, heavy use and high heat conditions ,and can leave you stranded on the side of the road. I upgraded to the Series Two fuel pump and it has solved all my Series One fuel pump problems.

Cheers

RX-8 40th Anniversary

Makes much more sense on why my other one failed. I will definitely look into doing that and seeing how the S2 pump fits into the S1. That would save me a ton of problems later on down the road. Thanks for your input gwilliams6!

gwilliams6

You are most welcome, Cheers

It really wasn't that hard to do following this RX8club DIY. :
https://www.rx8club.com/series-i-do-...ries-i-230326/

HeidePhillips

Thanks for the link.


gwilliams6

I did the DIY exactly as pictured and instructed step-by-step, and it worked perfectly, and I have never had any issues with it at all.

Cheers