M-ster

Hi guys, need a little help on this, I've done a quick search with nothing, if it has been discussed, kindly just point me the way, Thanks!

Well, I've just notice this today after a 20mins+- drive, up to 6krpm, around 120km/h. After I have parked my, I usually don't off the engine right away, so, here I am, got out of the car and notice this thumping sounds from underneath the car. It sound very much like a heavy base thumping from a car(closed door). It's not loud but very noticeable. Probably thumping away like a slow heart beat a little more irregular. And also notice couple spots of oil being expelled out from the exhaust. Again sounds like some kind of combustion happening in the exhaust system.

Is this normal, or is there any thing I should be looking out for.

Thanks!!

ranger4277

Sounds like a misfire. The oil doesn't sound good though. Find out where that is coming from pronto!

It shouldn't be mis-firing.. but mine does it too a little even after the "L" flash and only after it is good and warmed up.

Spin9k

Real dripping oil from ehaust = call dealer quick! You got problems (think how far that oil had to go to get out to there!)

beachdog

Could be coolant or condensation mixing with the soot in the exhaust system making it look like oil. Condensation not likely after 20 minutes but still could be if recent rain or car wash. The big tailpipes allow quite a bit of water to get into the muffler.

Ice Cold RX8

I don't know if this is your problem, but after a legthy drive, my exhaust gets really hot and after I park it, I notice that the exhaust system starts to ping pretty loudly as it begins to cool off. I hope this is what your experiencing, if not you may have a big problem.

M-ster

I'll further monitor it before sending it down to my dealer to check. Don't want them to mess it up further. If it's misfiring, what would i be expecting to hear at the engine bay?

I thought the oil from the exhaust is pretty common hence the soot that gather at the tip of the exhaust??

Nope, not the pinging sound form the exhaust, I know that's normal.

Thanks guys, so far the only possible problem seems to be the missfiring, will monitor it and see if the problem persisted.

cheers.

ranger4277

I noticed my misfire from a slight drop in revs with a simultaneous slight shudder of the car and the thumping noise from the exhaust. Only when warmed up too. The irregular idle was only sign that the engine was involved.

swoope

iTrader: (5)

the thumping sound i have heard on several occaisions has been fuel sloshing around in the tank.

probably to simple but it took me a couple of times to figure it out

beers

tripwire

Mine certainly idles rough. Is this what you're talking about. I kind of sputters I guess, not significantly but it's there. The dealer says that is normal because it is a rotary.

I don't know for sure as I've never had a rotary or even heard one other than mine. I suppose it would do me some good to find someone else with an RX8 and listen to it as I listen to mine.

Anyhow, it drives just great so I'm not all that worried about it. It certainly does not idle smoothly, but there are no fluxuations in the RPMs at idle either.

Let us know what you dealer says.

Racer X-8

Check your trunk for a nearly-dead stowaway! :D

Sorry... duh, ...

KKMmaniac

Hey M-ster:

I notice that noise with my car also, not necessarily after a 20 min. drive though. If it is what you're talking about, I think it is just the exhaust noise as the engine stumbles a bit.

I don't know if it is normal, but I don't think a completely smooth idle is normal either. I'm not too worried about it.

M-ster

Well, I've monitored the situation for the last few days. The thumping sound seems to be there after some 15 mins drive. And it sounds very much coming from the muffler, but I'm can't make it out if the thumping happens in the muffler section or is it from the engine and being amplified in the muffler section?? With the aircon off, the car does idle very smoothly.
I'll see if I can get more info before sending the car down to my dealer.
cheers.

Mr M

Be aware that the normal combustion sound of any rotary is fundamentally different to a reciprocal engine. The combustion inside a rotary engine is extremely violent, and can produce a poppy, almost backfire like sound. As this sound travels down the exhaust it can resonate and become deeper...

Listen carefully to the engine from the engine room, and watch it for vibration too. If you don't detect any misfires or rough running doing this, and don't have any performance or MIL problems, then your engine is probably perfectly fine.

(I personally love the sounds a rotary engine make, it just sounds more like a perfomance engine!)

M-ster

Thanks for your inputs Mr M.
The comment your suggested above sound very much like what I'm experiencing. If it's what you said, then I don't think there's any thing to worry. Just wondering if you do have the same thumping/poping sound from the exhaust.


I did monitor the engine bay as well, don't seems to get any unusual vibration or rough running. But this particular tank of petrol seems to be going down much faster then the previous.

Thanks!

ranger4277

Do you have the hot plugs and know which PCM version you have? Plugs might be a bit fouled. Mine popped a lot more when my plugs weren't in top condition. Supposedly the later PCM flashes "L" and "M" are better for the idle and low rev range.

M-ster

Finally brought my car to the dealer, the mechanic wasn't sure if there's any misfiring, the popping/thumping sound at idle doesn't sound common to him. But then if there're any misfiring, it would be heard from the engine bay but no unsual sound from the bay. As he did a light throttle test at about 1200rpm, he felt a little irregular output.
He took out one of the spark plug (it's a NGK plug) did not find anything unusual but since he did not have any replacement plug in stock thus the plug went back in. Will have to go back to him again once the plug arrive, then he wil on all plugs. Will update further.

Atacdad

I'm pretty sure i read in a different thread that a slight "popping" or misfire noise at idle is normal for a rotary. Perhps one of the long time rotor-heads (RotaryGod, you listening?) will chime in. The excess soot is normal, oil is injected into the rotor housing for apex seal lubrication and gets burned as a normal occurance. thats why you are supposed to check the oil more often...it gets used.