spark plugs installed incorrectly by shop
 

I'm 70 years old and my days of working on cars are long gone. My car is an 04 6-speed I have owned since 2007. Car has 104,000 miles and the original engine was replaced at 78,000 miles. I had a local AAA certified shop here locally who I have done business with for about 3 years install new struts for me and I also provided new after-market, United Motor Products coils, NGK plugs and wires for the shop to install at the same time. Car misfired badly after I picked it up and CEL showed code P0302 at the shop. The shop continued trying to correct the misfire but was unable to achieve that result and recommended to me to take it to a local Mazda dealer, which I did. The dealer found both leading spark plugs were installed on chamber 1 and both trailing plugs were installed on chamber 2. The dealer corrected the spark plug issue, cleared the codes reset keep alive and centric shaft profile. Then he recommended a compression test as the car now still misfires above 5K and has much reduced power as compared to the engine before the mis-installation of the spark plugs. Dealer speculated that because of the spark plugs being wrong, excess fuel was left unburned in the chambers and could possibly have resulted in damage to the apex seals. The dealer also doubted that the premixing of 2-stroke with fill-ups would help to revitalize the seals but said it was worth trying. Does any of this seem like a reasonable explanation for why my car now has no power?

Thanks in advance for your assistance.

Spark plugs COULD have caused damage, however it also could be the replacement ignition coils you purchased. Aftermarket coils are hit and miss with our vehicles, and often don't perform at the required demands at higher loads/rpm's.

A compression test may be a good idea, as well as having the dealer technician inspect the spark plug holes for damage while doing a compression test. It would be smart to have these things documented and on paper so if it is concluded that the incorrect installation of the spark plugs caused any damage, the original 'AAA certified shop' could be held liable/accountable to repair said damages. Hopefully however it does not come to that, I stand behind the first likelihood that the ignition coils are not meeting the demands of the ignition system.

Were the coils replaced because of issues or preventatively?
I don't think excess fuel would have damaged the seals, but it would have damaged the cat, and the cat would then destroy the engine. It should be taken down and inspected for clogging. If the car was having issues before the coil replacement, possibly that was actually the cat becoming clogged.

Misfires at high rpm are more of a cat problem sign than seals.

Thanks for the helpful replies.

The car ran beautifully when I took it to the shop but was just not quite as powerful as a couple years ago so, yes the coil replacement was supposed to be a preventative measure. The mechanic at the AAA shop did try replacing the coils which I had provided after I brought the car back with other coils that he sourced, but of course I assume the plugs were still installed incorrectly at that point so...

It just does not seem like a compression problem as the car starts and idles perfectly both cold and hot.

Try resetting the NVRAM (20 brake stomp) since they probably disconnected the battery to work on the ignition.
Definitely get the cat inspected, it's possible it was partially clogged or damaged to begin with and the misfires finished it off.
Good luck.

Thanks Cajun for the suggestion, Did the brake stomp thing with no difference. Replaced the UMP coils with oem units with no difference. Had the dealer do a compression test. They recommended I buy a new engine for $6,800, again.

They told me the front chamber average numbers were just below spec at 6.3 but the rear chamber numbers were lower at 5.8. They told me what the unit of pressure they were using was but I didn't quite get it kilojoules per hectare or something. The thing I don't get is this rebuilt engine had less than 30,000 miles on it since it was installed in 2015. I could understand the original engine failing at 78,000 but this engine, since it was installed, has been cared for as meticulously as the rest of the car. I did oil changes at 2k intervals and never ever let the oil get more than a 1/4 qt. low.

I loved this car. My favorite car I've ever owned but holy moly a new engine every 30k? Not sure what to do with this car.

I've been driving mine for about 2 years about every day with numbers like that, with no symptoms for a long time until a few months ago with hot start issues.
I think that isn't the root of your issue.
Did they check the cat?

Are you still on good terms with the shop that did your plugs wrong?
If so, I think the least they could do is take your cat off and inspect it.
If it's bad, I'd ask them if they could gut it or cut it out and weld a resonator in it's place until you decide what to do.

I don't trust the dealership to look past the compression issue in order to sell you a new engine.
When you say you got a "new" engine, was it a reman from the dealership?
Did they address the root cause of the failure?

The remanufactured engine was purchased from Mazda and installed by a local shop here. A different shop than the one I'm using now. Yeah I still trust them, I'm taking a different car over there next week for a timing belt. So a clogged cat could result in low compression?

Bring it to me. I have a compression tester and I can look over everything as far as the ignition goes. I can also check the cat for you. If you want to check the cat yourself, a quick way to see if it is clogged is to do a spirited drive, then pull over and look under the passenger side where the cat is. See if it is glowing from heat. If you can't or dont want to, we can pull the cat and check it or you can take it back to them to have them check it. I happen to know a local guy who has a good cat I can source for you if it is clogged.

Sounds good surf. I would appreciate any help you are willing to offer. I'm retired so shoot me a pm as to when and where is convenient so we can meet.

Driving on a clogged cat is how engines get killed (which may be why your current one has low comp at 30,000mi). So I'd minimize any driving you do until the cat is confirmed good or replaced.

Unfortunately, some dealers and most regular mechanics aren't read into the RX8's peculiarities and replace engines without fixing what killed the engine in the first place.

ha! I got you beat buddy. I had an 04 Auto high mileage putting out 56psi (3.8 Bar) @ 190rpm (uncorrected) that I daily’d for 2 years just fine. Lol. It was an A to B car. Perfect for work. Cold start in the AM, drive to work, cold start 8 hours later to drive straight home. Impossible to start HOT even after letting it cool off with the hood open for 30 - 45 mins.

But hey, it still ran fine. Revved the piss out of it daily to make any power to keep up with traffic but it looked awesome, sounded great and was a fun beater... until I wrecked it during a drift session :sad: :banghead:

I’m on my 4th RX-8 now. 6pd this time. Haha.

Thanks for the information gentlemen. I picked it up at the dealer yesterday where the test was done drove it home and parked it in the garage. I have another car I can drive so I don't have to drive the 8. I looked under the car after driving it home and didn't notice the cat in any way but it was a steady rain all the way home so maybe that kept it cooler.

The question I have is this: Let's say we determine that the cat is clogged and we either replace it with a good cat, or being unable or unwilling to spend the $ on a new cat, we take what is a less desirable option as I understand it and gut the cat, would I notice any difference in performance since the compression is already low or would it simply halt the deterioration of the engine? Thanks.

It's a definite plus for saving your engine, less restriction and peace of mind.
A new aftermarket cat capable of withstanding a Renny's heat will run you about $1k.
A dealer OEM will be at least $1700 according to a quote one member gave recently.
Just be sure it's bad before gutting it.
Usually a CEL & P0402 code will accompany a bad cat, so it possibly may be something else.

Fixing the cat stops the engine deterioration. The car won't get worse, it will perform as it does now (minus the misfires and whatnot). If you gut it you might gain a few horses but gain a check engine light and an awful stench.

So the cats I see on the auto parts stores websites for under $200 are not the answer I suppose. I'm not too wild about the awful stench part of the equation.

Yeah I wouldn't put a cheap off the shelf cat on a rotary, unless you're into replacing them every few months. They're not all bad, but the risk is too high, based on experience on this forum. AFAIK either OEM or HJS are the only reliable options.

I don't think it's that bad.
You're old enough (me too) to remember cars before cats, it's the same thing.

Mazmart sells new OEM cats for about US$1k. Can't imagine it being above 1.3k even with shipping and tax.

http://shop.mazmart.com/en/rx8-catalytic-converter

Removing a clogged cat stops the damage, but it doesn't reverse anything.

Also, it normal for the OEM cat to have a faint glow if you drove it very hard beforehand. I had that happen before and inspected the cat by taking it off and putting a flashlight through the back to ensure it's not clogged. But if you are just cruising around town gently and it's glowing, yeah it's dead.

As for the stench... Remember that it not only smells bad, it's not exactly great for your health. Some people like the fume, but petroleum products are known to become addictive to some. Your call here. Also, if you have emission inspection, you will need some kind of cat to pass it.

Being in Florida, there are no emissions as you know, so that would not be an issue. The "stench" is really not much worse that stock imo. I have had mine gutted for a long time and other than the CEL, I have not seen anything that would be considered bad. There is a slight increase in exhaust noise if you are still using the stock exhaust, but that would be minimal at best. I have also noticed a slight increase in power since the exhaust is more freeflowing over using a cat. Do not get auto part store special. I can tell you from experience that they cause more problems.

Thanks for the information gentlemen. So it is possible to determine if the cat is good by whether or not light will pass through it? If so that's good to know. Also I'm encouraged by the possibility that maybe the cat is the issue. Probably I will have the same shop pull it off and inspect it for me. There's just not enough clearance for me to be crawling around under the car while on jack stands. Someone smart once said you should know your own limitations. There seems to be a consensus here that if the cat does need to be replaced to steer clear of cheap aftermarket units so thank you for clearing that up for me.

I bought a cheap Walker car just for emission inspection.
It lasted long enough for that.
The last time I decided to leave my BHR resonated midpipe on cause it's such a PITA to swap it, and the shop thought it was a cat.
https://cimg8.ibsrv.net/gimg/www.rx8...310cf5b0d6.jpg

Time to update my situation. Many thanks to Jr. & Surfnlow for taking the time to visit me here in Florida and give me their advice.

I purchased a downpipe from Agency power and found a shop who would install it for me. The old cat was a disaster. The new pipe makes the car sound really good, not too loud just a nice sound. As for power, I think it has more power than ever and I now look forward to each time I start it up.

My takeaway from this is don't trust the dealer to care for your car the way you do and don't put much stock in compression tests if the catalytic converter is totally clogged as mine was.

Good news.
Thanks for the update.