I bought my RX8 about 2 weeks ago for $2850. Runs and drives nicely besides low compression causing flooding and such. I just got a compression test. Just came for some advice/help/any ideas.

2004 Mazda RX8 with 70,912 Miles:

New Starter
Coils, Wires, Plugs replaced
Oil changed
Air Filter
Radiator Flushed
MAF sensor replaced
CSS replaced
Cat Delete
All programs up to date from dealer (I work at a GM dealer: went to a mazda for this)
Throttle body cleaned
All electrical cleaned
I have both o2 sensors and will be replacing them this weekend: and re grounding all grounds as well.

CEL pops up from Uscan OBD2 bluetooth adapter as follows: P0138 (o2 sensor bank 2 voltage high i believe): Also get P2402 (evap system): Also get secondary air injection code(not a big deal seeing as no cat and no emissions testing in my state)

I also use bluetooth adapter to watch water temp which has never passed 214 while ive owned it.

I let it warm up before hard driving. I shut down with the classic rev ( i know thats a matter of opinion). I get it to 6500 RPM's about 2-4 times a day. I run 3 quarts of 5w20 (conventional) and .7 quarts of 5w30. I run 93 (real 93 not cheap 91) and do not premix.

It obviously floods because of low compression... ALONG with this problem it runs extremely rich (it burns my eyes when in the shop) but only sometimes.... ill hear a solenoid click and it will start running rich(along with a bit of clearish smoke) and then click and it will run less rich but still rich none the less. And obviously it has the classic hard start when warm issue (about everyother time).

Is this due to low compression (which i have as youll see by my numbers) or could a bad front o2 sensor be sending too much fuel into engine and flooding it out?

compression results:
rotor 1: 5.7 KGF/cm2
5.6 KGF/cm2 at 274 rpms
5.3 KGF/cm2


rotor 2: 5.1 KGF/cm2 (oh no)
5.6 KGF/cm2 at 278 rpms
5.1 KGF/cm2

So obviously there is low compression: no doubt. but given what I said any ideas or is it absolutely definitely bad seals and needs a rebuild (which i will do by myself) also is that the cause of my running rich problem?

THANK YOU IN ADVANCE ps. tell me if i missed anything

 

Your exclaimations of "oh no" on the rotor 2 numbers really isn't well founded. The highest rotor you have is 5.7, and at that RPM, it normalizes to a 5.4. 6.9 in the point at which it fails. All 6 of your rotor faces are failing, and they are all failing rather badly.


Trying to diagnose other issues with a known problem of compression that bad is rather pointless. Solve what you know is wrong first (the engine), then worry about what else is wrong.

The only time I would reverse that advice is if the engine blew it's seals from a failing fuel pump, since you don't want it to blow the replacement. But your seals are clearly still intact, just heavily worn.

 

Thank you very much. And I know that the oh no isnt really warranted, I know they're all failing, I was trying to find that quote you had and hey it showed up pretty quick thank you very very much. Well how much should I pay for a good rebuild kit? Im about $3480 deep into the car. I just hope that I am not being to much of a noob (i knew i needed a rebuild I just wanted to hear it)

 

Rebuild costs can vary greatly. $2,500ish minimum for a rebuild that isn't just going to fail again in 10,000 miles, or upwards of $5,000 if you end up having to replace every single part (which is really just a replacement of the engine at that point). Unfortunately, since you have an automatic (found the reference in another post of yours), you have a 4-port, which is the most expensive of the engines to buy a reman for, just because of the much lower volume that they have. So even buying a reman will probably run you $4k+.

 

Sorry more noob questions:

04-11 Rx8 Automatic Master Rebuild Kit

is that not a full rebuild kit?

 

That is a full "rebuild kit", however no rebuild kit includes any of the 8 major engine pieces though:
- 2 rotors
- 2 housings
- 3 irons
- e-shaft

And it is highly unlikely that you will be able to reuse all of those.
Housings will often have chatter marks, missing chrome, or scoring, and can't be repaired. Replacement will be $1,200 each. These are usually the big extra cost on rebuilds.
Irons may be groved out of spec and needs lapping or replacement.
Rotor seal seats may be wearing through the hardened metal they sit on and become out of spec
e-shaft bearings may have copper showing

So that rebuild kit is the bare minimum that you could get away with, but if you don't replace the major components that are out of spec, the engine WILL NOT last very long at all. And you won't know what is reusable till you tear the engine down.

 

PERFECT!
thats what i needed to know thank you so much and I will update with any questions or breakthroughs.
Regards all