Couldn't think of a better title, anyway I recently bought a used 2005 Mazda Rx8 with ~78k miles. So far it's been great and I've had to do a few little DIY things. Today on my way home from work I noticed a popping sound sort of like something was either dragging or bouncing around in the exhaust. It seemed to only happen after I punch it and let off the gas so I don't go over the speed limit (I do this often and this is the first time I've noticed it) so I took a 30 minute detour (probably not the smartest thing) to try and hear the sound again and I can confirm that it only happens after I punch it (driving it easy doesn't cause the noise) So on my last run of trying to hear the sound (trying to pinpoint it) I heard an awful ripping sound, I almost thought it might have been the belt. but it sounded more exterior then interior (i'm not ruling out the possibility of it being inside the engine) So my reason for making this post is to see if anyone has had anything similar happen or if someone can point me in the right direction because I don't want to run it with the possibility of damaging something more then it already has.

I should note:

I have the 4spd Auto and have been playing around with the tiptronic feature recently, the other day I fishtailed on accident and now i'm in love with RWD and its' possibilities. (I should also note this is my first car) so It's safe to say I've been driving it less then ideally I've been getting around 10mpg, roughly. Anyway my reasoning for mentioning this is my tires, they're pretty bad, I am definitely getting new tires soon but the rear right tire is an oddball. So I am thinking my recent driving behaviour could have ruined the already worn tires. I don't know much about tires in general but aesthetically they look fine but i'm really hoping the ripping sound and potentially even the popping sound came from the same place, if not I could have 2 completely separate problems on my hands. Any advice would be great, thanks.

P.S the car drives good, accelerates good, and generally sounds good when revving it's just the popping that happens after, now that I think of it, it could be misfiring? Thanks again.


TL;DR Popping sound after accelerating to a high rpm and completely taking foot off the gas to slow down to a more reasonable speed. Ripping occurred on last run thus scaring me enough to finally make an account on here and post this thread.

 

Did you manage to blast a hole through your catalyst? Pull it off and check, if it's empty or has a massive hole through the honeycomb then the popping is expected.

How old are you? I feel like you're the kind of person to hang out on reddit, not research things before you buy them, and assume they know how to drive well.

Read this and get a compression test.
https://www.rx8club.com/new-member-f...t-here-202454/

I'm certain you haven't fixed any issues that this car usually has when bought used.

 

Congrats, and Welcome to the forum.

The pop at higher RPM or during spirrited driving is normal.
If it sounds something like this video then you are good;

Also, read the new / potential owner thread in newmember forum thoroughly it will help you tremendously. Inspect your CAT, 2 ways of doing it. Drive it hard at night for 30-45 minutes pull over in a safe place and look underneath the car to see if your CAT is glowing RED.

2nd option, Take the cat out, inspect it to see if its broken, or clogged.

Post more info about your car, and feel free to ask any questions or concern you may have pertaining to your car.

Once again Welcome to the forum.

All the best

 

Not a 100% certain if you should hear the pops with the CAT on..

 

That's afterfire, not backfire. A clogged cat won't cause afterfire, a broken or missing cat will allow it. With a cat it's really unlikely that you'll see it.

The popping is usually a less visible afterfire, caused by de-advancing timing rapidly (when you let off the throttle), dumping a little bit of excess fuel into the exhaust.

 

To address your comment about my age, I turned 17 the 3rd, I've done what I believe to be a sufficient amount of research to be able to maintain my 8, before I purchased it I got it compression tested by Jeff Gladish from Maztech in Tampa, Fl. He said the compression was adequate and to add 1 ounce of premix to every 200 ounces of gasoline to help the compression. I also go the oil changed to non-synthetic 10W-30 oil which he had recommend. I was having a few issues with the A/C and ended up doing a few DIY's found on here, MAF sensor cleaning, Wrapping the A/C tube in pipe insulation, cleaning out the air filter behind the glove box etc. I let the car warmup for about a minute until it's roughly over 1000 rpm idle then I go keeping the RPMS under 3000 until the needle is right at the middle (has never pointed straight up and never gone past the middle line) I've filled it up 3 times since I got it and have checked the oil to see how it's burning, so far so good. I feel like I am competent enough to keep my engine healthy. You probably figured I was from Reddit having the TL;DR, I tend to browse but never post. And the comment about my driving, I believe I'm a decent enough driver with a good head and enough common sense, although i'd like to get better (as far as stunt driving/track driving) Anyway sorry for the wall of text and thanks for the replies, but to answer your question as a whole I think I've done better researching and have more knowledge of the car then most adults did when they bought them, or else the 8 wouldn't have such a bad rap.

 

I'm not very good at Forums, never been a forum guy hence why i'm just now making an account and posting on here, so I am unsure if this is how you properly quote but what you just explained might have been what I was hearing. Doesn't explain the ripping noise though. Could potentially be my tires? as I said they were worn down before and after the way I've been driving I wouldn't be surprised, but like I said I know nothing of tires and can't see any visual damage.

 

When you said your right rear tire is oddball, did you mean it's a different size and/or brand than the other three? Or just worn more? If it's a different size, then stability or traction control is more likely to kick in, and that can be accompanied by an unpleasant sound.

Ken

 

I believe it's just a different brand it may or may not be worn more or less than the others as I am unsure when they were last changed, they are all worn though, that's for sure, and I plan on getting new tires very soon, if for nothing more then to have all 4 the same. I believe that will help improve my MPG, it's also often forceful to turn the wheel to the right as if the wheels aren't aligned. I got a front-wheel alignment a couple of weeks ago, afterwards it was better and then a few days later it went back to the way it was previously. That may be a whole other issue but I feel certain it's the tires. That or i'm just a wimp.

 

Well it's good to see you're not a total noob, sorry about being brash earlier. Could something have flown up into one of the fender liners, tearing it? IIRC they are reinforced by some type of string mesh, which could sound like tearing.

Have a look at your fender liners, belts, and the interior walls of your tires.

 

Thanks and that's probably a good idea, the popping and tearing could be 2 totally separate things I just never noticed before. I am pretty certain the rattling isn't something lose. I remember reading in the common symptoms and problems something about if you heard rattling and that's what put my alarms up. I'm trying to be as smart as I can with my 8 and getting the most out of it. I really didn't put a penny toward it but I value my parents' money as if it was my own. (I am paying for everything else though gas, insurance, any future mechanical problems, aesthetic changes) all of which I could afford right now so I am overall in a happy place with my 8.

 

Yeah, I think the tearing is something else entirely. Do you have any CELs right now? Have you replaced your ignition coils recently? That would definitely lead to excess fuel in the exhaust, bad mpg, and all around less than ideal performance.

Does it sound like something metallic rattling inside your exhaust? That pet strongly points to a cat that's been broken in some way.I suggest pulling it off and having a look, it's really only 3 bolts at the header and 2 at the catback.

 

I am unsure what CEL(s) are, and I haven't replaced the ignition coils, that would essentially be a tune up, correct? And Jeff from Maztech said the coils looked good when he did the compression test. And it does sound like something rattling in the exhaust, maybe something loose because when I drive it like a civilized human being I do not hear a thing. It just seems like a pain in the *** to get up under this car haha.

 

Sorry to tell you this but I have never met a 17 year old that could drive for **** (this includes my self at that age) and assuming that you can is going to get you in trouble (not trying to bash you just trying to warn you). Next get the odd tire off the back end of the car different tier brands can be bad and cause all kinds of issues not all brands are the same size even if they state they are (I know this for fact through personal experience). Next a CEL is the check engine light. Next most mazda mechanics know squat but yours seems to know more than most. Next even if your coils "look good" looks don't mean squat most last up to 30k miles and even more fail far befor that time. Your milage could be a indication of clogged CAT, bad ignition,or your driving habits combined with the other two. Did your mazda tech give you a sheet with you compression test numbers on it if not don't take his word for good compression (dealers will lie cheat and do anything to sell you a car) good compression would mean it's higher than ok. Ok compression would mean you have a failing engine but not enough that it's time to worry but should be ready to start saving for a replacement.

 

Awesome, I wanted to start off by saying thank you tons for all the answers, comments, and help. As of posting this I've figured out what's wrong with everything I've mentioned in this thread. As in response to niteshade247 I will have attached my compression numbers. He said they would be roughly a point higher than what he has written. From the get-go I have accepted that I may need to rebuild the engine soon and at the moment if it did need to I have the available funds to fix it. I have no check engine lights, I have replaced all 4 tires with brand new 225/45R18 - 95W Firestone Firehawk Wideoval AS tires. The popping sound turned out to be a piece of plastic that had gotten torn off by the front left tire (not visible from standing distance, had to get on the ground to see it, if it wasn't for my mom driving behind me I would still not know, she saw it flapping as she drove behind me), whilst it was still bolted on in the back so the piece was catching wind and when I floored it, the piece essentially was forced to the ground which happened to cause the scratching/scraping. Funnily enough the first time I really heard the "ripping" sound was when I floored it turning right (the wheel was pushing the piece down and then the wind did the rest.) Turning the wheel right has also been easier as I've bolted the piece of plastic back so there is no more resistance when turning right. Now it rides like a dream, I don't have any issues steering, and I feel like after about a month and a half I am finally starting to know what it's like to drive my 8. Thanks again for all the help, turns out it was something minor (hooray)

P.S @Niteshade247 you're most likely right about my driving, I don't want to come off as cocky but at the same time I don't want you guys to think of me as a horrible driver, I've been driving Go-Carts, ATV's, Pocket Bikes (Miniature sport bikes), a Mini Harley, my parents' cars, I even drove a bus once when I was a kid. I have experience behind operating motorized vehicles but I know i'm not at a level to be considered great... or even good.

 

I wasn't trying to be a *** and glad you really didn't take it like that. Just have respect for the car it's no 500HP vett but it can still hurt you and others as soon as you think have it under control. Glad you figured out the noise that peace is important to your cooling system glad you didn't rip it off. The numbers look right but I wonder why he added the 6.6 to the (guessing) front rotor. Having front and back rotors be off by a full point on a failing engine (from what I've seen) is typical. Not really bad numbers but yeah save for a rebuild enjoy the car till then and wellcome to the family. Grate guys on here and as long as you do trouble shooting before you post problems a lot of them will be more than willing to help.

 

Hey no problem at all man, I know teens especially often make mistakes and i'm not at all above making those mistakes, and I will continue to be careful when driving. Also, I assume he took the overall average? and made it 6.6 he also said the premix would also help improve compression. I believe if I take care of it properly it should last me a while. I will also try to further inspect my car before posting on here, it was something rather small but I was panic'd and wanted to get a post out as this is the first abnormality I've come across.

 

That's the sketchiest compression test I've ever seen, but congratulations on fixing your current issues!

Definitely replace the ignition coils as soon as possible, they can destroy your (very expensive) cat, which can destroy your (very expensive) engine. Then I'd look into getting an upgraded starter (220ish RPM is really low) and check the health of your battery. The starter could probably push another couple of extra months out of that engine before you really need a rebuild.

 

Could you elaborate on why it's sketchy? Jeff from Maztech looked at the coils and said they looked brand new. And are you saying if I don't replace the starter within x amount of months the engine will definitely need to get rebuilt? I'm sorry, I just want to do the right thing but you're saying stuff about my car when you really haven't had a chance to look at it in person. If you're being genuine I thank you for the advice and I'd eventually like to get a tune up so I can keep track of it. Upgrading the starter to the newer models' starter wouldn't be a bad idea but personally I have yet to have a start take longer than 2 seconds. Hot or cold.

 

Coils can't be evaluated by sight alone. They can be completely clean, with no arcing spots, and be totally shot. Looks mean absolutely nothing. They're cheap to replace, just do it so you know the condition of all the parts in your car.

I say it's sketchy because rotary compression tests are usually absolute, meaning the numbers given to you shouldn't need to be shifted in any direction. They're also usually not hand written, since the tester is all digital.

I'm not saying that the starter is causing any problems, I just mean that a stronger starter will help a dying engine get started much more easily than a bad starter. You'll have to get a rebuild anyway but if the starter is very good you could probably deal with the dying engine for a few extra months. Once compression drops a bit more (who knows how long that could take) it will get really hard to start.

Coils are what you should be primarily concerned with. I still suggest pulling off and checking your catalyst for clogs. There's not much else that will destroy your fuel economy than those, and they're usually related.

 

Premixing won't boost compression ether unless your poring it in at really high amounts. Premixing is for safety to keep from engine failure due to OMP failure as well as better lubricant to the center of the apex seals because the S1 has only 2 oil injectors where the S2 added a 3rd per rotor to combat the lack of oiling on the center of the rotor. So it won't up your compression but if your mode of failure is due to wear it can help lower the rate your engine will die. If it's going due to carbon buildup or any other mode of failure it will not help. Change those coils bad coils can add to carbon buildup as your not burning your fuel like you should. Check your CAT if you can (no smog inspection where you live) put a mid pipe on. Back pressure is the enemy on a rotory and can end the life of your engine unlike a piston engine where you need some back pressure. Cooling system is one other failure point that can and dose kill a lot of engines. All you need or could ever want to know is here on the forums you just need to serch for it most of the grater important things are stickied.


Edit
Yes a upgraded starter is a bandage for a engine with bad comprssion. It won't fix it but will help start it.

 

Alright well thanks once again both of you for clearing that up, to be quite honest my parents have been helpful a lot in the financial area of essentially buying me the car, wheels, fixing a few things on it. They just wanna make sure if/when the engine blows I have the money to fix it, that aside they're being stubborn when I try to explain to them about the coils, and is there a specific set of coils I should shoot for? Also, isn't the cat a bit hard to get to?


Edit: I should add the reason they're being stubborn is because the guy where I got it compression tested said they looked brand new, and my parents (they're kind of old timers) and they don't know as much about rotaries, haven't done the amount of research I have, they think it's fine, but I know this forum is a great pool of information to draw from but they're just being difficult. I'll eventually talk them into it.

P.S I can go and do it myself but I hate going against my parents, I want them to be okay with it.

 

Use OEM coils only. No eBay no auto zone specials. The only other coils that can be used are LS1 ( I forget the numbers) but this swap can be riddled with problems or BHR coils (these I have and most others do as well) the advantage with BHR is never having to replace them ever again they have a 1% or less failure rate. The only draw back is they can cost upto $600 (if you get the full kit that would be coils,wires,and plugs. This is advised ) but if you ever decide to part out the car they are the only coils that have resale value. You could even find a set another member might be selling here on the forums.

Edit
Yup forgot about the BWD coils. Those are proven safe too.

 

Depending on where you are, they are readily available through most good automotive stores (Autozone in US, Parts Source in Can.) Try to get the BWD/Intermotor brand if you go with a parts store. Mine (canadian price) were about $35. each. As for the cat, all you need is a socket set, a way to get the car off the ground enough to crawl under (when it's cold) and a bit of elbow grease, The cat is part of a pipe that goes from the exhaust manifold to the catback (rear muffler/pipes assy) and fastens with 3 bolts in front and 2 or 3 at rear.

Perhaps, if your parents are going to play a big role in your RX8 experience, you might want to have one or both read through this thread to learn more so they can offer informed help and opinions:

https://www.rx8club.com/new-member-f...t-here-202454/

 

Alright well I've decided to go take it for a tune-up tomorrow. I'm not very savvy in the mechanical area and I'd likely break more then fix anything. I am thinking about taking it to Tires Plus. Any thoughts on this? I know i'll likely get charged an arm and a leg but I really don't care at this point.