Quick Tech question
 

Hey guys I have a quick question to ask you about my 2004 mazda RX8

History:

The owner bought new in 04 (my boss) and has had oil changes done every 4000km since new , also has done spark plugs when needed .

The car has 133,000km on it with a 6 speed and still runs like a champ i can beep the redline in all gears and it pulls hard . I take it to redline once a day and check my oil every 3 days or so , no premix in my oil either . I just bought this car and am new to rotary but have been reading alot and getting to know them .

The car idles smooth at 850-900 rpm and always starts up perfect when cold .

Now here is the question which i have researched the shit out of but couldnt find my exact problem . After I drive the car around all day and stop to go into a store and come back out and start it when its hot it stumbles . (It always starts when warm) It will take about 1-2 seconds and stumbles and burps and farts around 300-500 rpm for a second or 2 and then jumps back up to normal idle . It doesnt start in 1 second jump up to 1100ish rpm and then fall to 800rpm , kinda starts at 800 , then down to 400-500 and farts a bit and then back up to 800

Is this because when the housing is hot it expands making the compression a little bit lower ?

I do belive it is the original coils in the car ... which im thinking might be a bit of the problem .

unfortunately, this doesn't sound too good... Sounds like loss of compression, and you are well out of warranty :(

If the coils have 133,000km on them then they are wayyyy past when they should have been changed... That could definitely be your problem.... If they are that old, then changing them out will give you better performance all around, including starts

Ehh, maybe not in this situation.... The fact that it still starts in 1 to 2 seconds (even though it is a rough one) is far from not starting at all, which a lot of low compression engines do... Also, there are things other than low compression that can cause trouble with warm starts (like the starter, coils, etc). I would say that since coils being bad can cause them not to operate well warm, and his coils have 133,000km (over 82,000 miles) on them, there is a good chance that the coils are bad and are causing the problem... Obviously low compression is always a possibility when there are warm start issues, but based on the circumstances I wouldn't jump to it immediately... Try switching out your plugs/coils/wires and see if that fixes up your issue.

Keep in mind that for the Renesis, a low compression engine can still be started normally in many situations unlike previous 13Bs.

I would say lateralus is on the right track. If you believe the coils are as old as you say, replace them. And, you might as well replace the spark plugs and wires at the same time.
Have you tried to pull any error codes from the computer? That may give us some indication of what is wrong.

wouldnt low compression affect more then just a warm start up ? the car all around runs very solid and cold start is fine , up to 2000 then down to 1500 and then 1000 then finaly 850rpm . the car has always started and even starts warm fine 50% of the time but sometimes it just stumbles a bit thats all . got coils , plugs , air filter , wires all comming . I just hate things in the back of my mind about the car thats making it not as fun to drive as it should be . Plans are to drop a 13b rew tt in it later down the road , but am lookin for at least another year outa this engine .

I totally missed the part on coils! damn New years drink... Yeah, it always sucks when you can't enjoy your ride like you should. Mine is stored for the winter...

If it was low compression, it wouldn't start when it was warm or it would die when idling. I wouldn't totally rule out compression, but I think you will find your problems elsewhere.
The 13B twin turbo isn't all it's cracked up to be. Stock it only made 15 more HP than the Reny. And the maize of vacuum lines were a nightmare. Most that modified the FD went to a single turbo. Going to the REW will mean changing out the PCM and that cripples this car. Enjoy it for what it is, or get an FD.

Agree with Al..

Also 13B REW you need to modify and change engine mounts, and lots of add on engine bay parts.

I would go for new plugs and coils and wires first.

And you still have 27thousand km on core warranty anyway :)


( If you live in Canada anyway :) )

It looks like the usual routine for a car with that mileage...

Get a compression test done after you have inspected your catalyzer. The 2 may exclude inspecting (but not replacing, they're old anyway) the following:

ignition system (coils, wires, sparks)
Fuel pump
Starter motor (have you got the new one?).

That's pretty much it.
As for the car pulling strong i'm not sure what to say... have you ever driven an rx8 with a healthy engine? If you haven't then you also lack the capability to compare yours with a good running one.

Thanks for the response guys , I appriciate it , and yes I drove the car back in 04 when it was bran new . I just see it being a bigger problem in the hot summer . I'm gonna see about getting the motor rebuilt , what does a full rebuild usualy run ? The renisis has removable apex seals correct ?

Rebuilding an engine is not worth it most of the time if you want to do it right and after a lot of miles covered in doubtful conditions.
The housings alone cost around 1200$... go figure. Rebuilding an engine is not like slapping 6 new apex seals and calling it a day. There are parts that need to be replaced, others have to be inspected etc. You only know what you're going to spend when the engine is torn down.

On the bright side though there are vendors on this board that offer good remanufactured engines for dirt cheap given their quality. I had a chance to try an engine rebuild by Mazmart and was amazed. Other vendors also do rebuilds, including performance ones, but i don't know their prices. The quality is still top notch though.

Update if someone reading this with same problem . Put in new coils , spark plugs , air filter , changed oil with filter , dropped tranny fluid and changed that ........... car runs as good as new and does not stumble what so ever when warm or cold or hot . Back to beeping the gears with a smile on my face:djcelebra

How much does new coils cost and is it something I can do myself?

Around $45 a coil and yes you can do this yourself

Yup super easy to do , followed the DYI on this site .. mine were $50 each . I have pretty much found all the info I could ever want on this site , spend some time searching and 99% its been asked before and answered:wiggle: