Engine Knocking - Please help
 

Hi there,
I recently bought a RX-8 2004 second hand 64k miles, but when I start the engine there is a red light on the gauge also the yellow engine light and knocking sound from the engine also RPM under 1k. The previous owner made a Mazda service check and they established that this is common RX-8 problem. I check that the last owner put fully synthetic oil and this is very wrong for this model.
I read a lot of threads and I know that probably I will need a engine replacement but if there is chance to fix it please let me know. Thanks

Synthetic oil being very wrong?

Do the usual routine checks. Compression, ignition, possibly reset the e-shaft profile etc. If it's just shaking check the engine mounts.
Knocking and pinging may depend on a bunch of different factors. Make sure that it is actually what's happening.

here's a silly question, what kind of fuel are you using

Thank you guys for the fast answers.
I forgot to add something very important - the engine has difficult start.
I will try tomorrow to reset the e-shaft profile. The oil he used is 5w30 Fully synthetic, I'm a little bit confuse, everybody are telling me different oils.
About the fuel, I'm not sure because I'm still using the last's owner reserve.

You probably bought a lemon... do a compression test!

...and figure out whether you have any warranty coverage, either with the seller (if it was not a private individual) or with Mazda or both. A little searching here will give you plenty of information on the Mazda side of this suggestion.

If I understand correctly .. you said knock at less than 1k rpm

You maybe hearing something.
But it's next to impossible to get the engine to "knock" at idle.

OK ok .. yes it can be done if you set out to do it, as in change the tune.

After that, use the highest octane (supreme). It might solve the problem on the knocking issue.

Not if there is a "knocking" sound under 1000 rpm.

First thing... Which "red light" is on?
Second... Find out what codes are stored by the check engine light.
And lastly... I don't see anything in your description that is a "common RX-8 problem."

Thank you.....................Jeez! :doh:
I have no idea why it took this long for someone to ask these simple, basic, yet important questions?????

thanks! and which YELLOW light?!?>!?!

FYI...synthetic oil will not wreck your motor :)...it is freaking oil for *#*#*'s sake.

Some markets Mazda even suggests using 5-30 Synthetic....so that isn't a worry

Check out the codes and get back to us :)

Classic RX8Club. I'm surprised the usual numnuts didn't tell him to seafoam the engine, etc.

Thanks for the info guys. This is the best forum!

The lights are:
"Engine coolant level warning light" <-- I check the coolant is Ok
"Check engine light" <-- The diagnostic says "Internal fault" common for RX8.
Today I was unable to get over 4k RPM. The car now is in the service for compression test. Is the engine completely dead or there is a little hope to fix it?

About the warranty - I'm the 8th owner may I use it when is under 100k miles? Curious why the previous owner didn't make nothing. Even he told me that "unfortunately i do not have the time, resources or money to look into", so I guess no warranty.

Don't waste anymore time and ask Mazda. They should be able to tell you if they have the required maintenance records.
It doesn't look to bright btw.

I think you should try seafoaming your engine, that will probably fix things right up.

Isn't this the cut off when an engine is cold?
Was your engine warmed up before you tried to rev?

Aww... You beat me to it. :mad:

He has a series I 2004 model. I still don't get what and how the "internal fault" a common problem :dunno:

The result is low compression. I left the car in the local service to open the engine and to try to rebuild it. I hope that all the problem will be solved by replacing the apex seals or the side seals on the rotors. Tomorrow or after tomorrow I will know for sure.
Thanks for all the advice guys.

You said the car was under 100k, take it to the dealer and see about getting an engine from Mazda. If you are under warranty the engine is free and you just pay the diagnostic fee the dealer charges.

That's true Cohort but unfortunately, I'm the 8th owner and I bought the car abroad, so no more warranty.
Does anybody know the size of the stock Mazda OEM Apex seals in 13B engine?

For anyone that comes across this thread from a search. I know it is an old thread but just to update information.

The knocking you hear is one rotor face experiencing a misfire, could be bad fuel, bad oil, cracked seals, coked up plugs or rotors, overheating, bad sensor causing computer to fuel bad and so on. It is easy to call low compression which it most likely is but there are a few things that can cause low compression in the 13B for instance using a 5W30 which aftermarkets recommend yet Mazda recommend 0W20 can cause this issue, fixing it will need either a rebuild or cleaning.

with the use of 5W30 or thicker oils at 100'c causes the OMP pump to meter the rotary oil in the cylinder to be less. It will suffer from oil starvation in the cylinders. The pump can be adjusted for different oils or the pump modded to be supplied from a separate 2 stroke oil bottle. The reality is that the engine is setup and metered for 0W20 and as of today modern high quality oils are much better than they used to be years ago.

All this said, the Mazda RX8 is a sports car, it is a high performance engine and will require allot of love, constant rebuilds and work to keep running as does any sports car. This is a not a car suitable for everyday runs to work and back, it is a mean machine designed to be driven not transporting.
It is best to buy a spare engine and rebuild the spare while you use the other and then swap the engines over when the used engine needs a rebuild. I'd say the RX rotary cars are a petrol-heads car for sure, far beats anything else for sure, just know that you will need know how to take out and rebuild the engine like you change the clutch on a normal car.

Last time I checked the recommended oil in North America is 5-20..

Changing to 5-30 will not change the OMP output as oil is basically non-compressible and will not alter the pump output as it is a positive displacement type pump that injects a volume of oil based on the piston positions.

Literally none of this is accurate or recommended. Why did you post it?