Please help Diagnose???
 

Hello,

I will just cut to the chase. At idle the car is making strange perhaps rubble, clunking, shaking vibrating noise. It is more noticeable from the inside, goes away when adding some rev. Not so noticable from the outside or nor from the underneath. I can hear the noise from the engine bay sort of from the oil dipstick side of the engine, sounds like it is coming from the rear rotor area??? The idle jumps and drops under 1,000, like a rough idle, but goes away when reving up. From the outside by the muffler I can hear pops cycling every 2 seconds about and when that pop happens the car sounds to be cutting off. My thoughts on this so far are, spark plugs, coil pack, spark plug wires, bad battery, bad rear rotor, apex seal/s and thats all I can think of so far...

In the mean time I will be searching the forum but would appreciate any help.

Thank you

Bump, I still have nothing... Anythoughts?

Perhaps a video clip to watch so we can observe the sounds ourselves would be more helpful.
Or else we'll just be playing the "Guessing Game" while you swap out random components.

True I will do that.

My guess is its the coils

Well I never got to the recording video of sound, sorry. Figured with all the vibration, cutting off rpm and weird clunking noise from the inside, I'd just take it to the dealer. I just couldn't find the noise source. Like my suspicions before I was heading in the right direction but before throwing parts at it I figured I see what Mazda had to say. Confirmed that coils, wires, and plugs have to be replaced. It was time and I missed out on that maintenance part and defect I guess from what I read in the past. Also, engine mounts which it would of been the the more obvious thing to guess, but I missed it... Funny thing, the dealer claimed telling me that while he (service writer) and tech. sat in the car the instrumental and all other lights inside the car started flickering on and off...? He asked if I experienced that and I told him nope never, he then say "I noticed you have after market bulbs in your doors", and he left it at that...? I don't know what happened there but today when I took stuff apart my positive battery post cap was broken, all I can say is they suck for breaking it and not telling me or atleast fixing it. So, I will finish hopefully this saturday replacing the parts and I will do further update on the engine performance.

did they inspect your engine mounts?

Oops... forgot to menytion that part. Yes, engine mounts have to be replaced to doing that this weekend.

Okay car is fixed, turned it on and drove it around. Idles smooth and pulls strong, will see how it plays out. So here is what happened for those who encounter same issue.

Symptom:
-Rough idle with rpm drop and engine surge, strange clunking sound at rpm drop. Surge would go away at 1,000 plus rpm and never seemed like there was anything wrong at higher rpm.
-Power seemed lacking before.

Repairs:
-2 new engine mounts
-4 new ignition coils
-Spark Plug wire
-4 new spark plugs
-New Optima Battery

Cheers,
Adam

Awesome thread. My 8 is doing exactly what yours was. Do you have links and prices for everything? Thanks for the info, hope everything stays good for you.

^^ Ah yes, the oft overlooked [total] ignition system. ;) Motor mounts as well.

Glad you got it sorted.

oh yeah, how can you tell if you need new motor mounts? is there some type of indicator?

Yea thanks and your welcome.

For engine mounts: after the car warms up or even is driven around for a few minutes either or is fine. Stop, allow the car to idle, if must put the A/C on for a heavier load on the engine. As the car stands still, at idle you want to start to check by looking under the bonet (hood) lol. If you see the engine shaking that would be a good sign. After I swapped the engine mounts it was not shaking at all. Still as a statue, if I may. Also from inside the cabin the rpms drop after before and more so after the a/c came on. This was a second part I looked into, diagnosing that it was for sure spark plugs, wires and coils which I haven't changed the coils nor the wires since new (I missed the thread and TSB on that flaw). The engine had a rough idle so that it made a strange clunking noise, after changing all parts it now runs smooth like new.

As for prices in all plugs, wires, coils, and mounts I spent $600 give or take a few dollars. Pretty prices but thats Rx-8 maintenance. If you are looking for dealer work, i.e. here in Chicago, as each dealer has different prices and rates on everything, one dealer wanted $1,500ish for parts and labor =o

Hope that helps, if anything is hard to understand what I wrote as sometimes I tend to write like that, let me know I will try re-explaining my confusion. =)