Thought I'd post this to help others...

Recently, I'd experienced hard starts w/ my '04 (~70k miles). The engine would crank and fire intermittently, and would finally start. I still have the original (low speed) starter and have had no issues starting before this. I have an Optima yellow top battery that's less than 2 years old, and cranking is still strong.

I also noticed a lack of low-end torque (not that the Renesis has much of that to begin with...) as evidenced by a "stumble" coming off a stop sign (I have a MT). Above 2k rpm everything seemed fine, but once (and only once) I got a flashing CEL during hard acceleration to 8500 rpm. I had the code pulled and it was a misfire on rotor #2.

This was slim evidence, but, coupled with the fact that the coil packs are a known issue, the number of miles on the car, and the fact that I'd replaced the plugs and wires only 8 months ago, I took a chance that it was a weak coil pack.

I replaced all four yesterday, and it immediately solved the problems!

BTW, Rosenthal Mazda (www.finishlineperformance.com) had the best price I could find for OEM coils, shipping was free, and I got them in 3 days (I live in Missouri).

Also, I did the simple resistance checks suggested by the Mazda service bulletin, and all of the coils I removed checked normal. So, this method alone wouldn't appear to be a reliable way to diagnose a coil problem.

The DIY's on this forum are a great help. I replaced the coils in an hour or so, and I didn't have to remove the air box or stabilizer bar as some have suggested.

 

This only reinforces what we've been trying to explain to others.
Method you used is a reliable way to check the coil windings, but that isn't the component known to fail... its the ignitor.
There is no way for you to bench test the coils... and yes, no 'visual' way to tell either.
Only real way to test a coil is individually with a timing light.

Glad new coils helped with your problems, I only hope that this doesn't make the inexperienced members think that all starting issues are related to coils (since we already see them blaming coils for everything else).
Without proper troubleshooting, you won't know unless you want to throw random parts at a problem.

 

I had all four coils replaced on my 05, after I bought the car on Sept 10th. The 6speed had 87k and had 30 miles on a factory reman engine, so I had nothing to compare it to. The car seemed to run good, but after reading many threads about coils, and noticing the extended time to start, and the chirping sound as the engine fired, I had the coils replaced.
WOW! What a huge difference, it felt like it gained 30 horsepower! I can't believe it ran so bad, until I did this, now its a badass!

 

Post #3 here details the benefits and penalties of ignition health: https://www.rx8club.com/new-member-f...t-here-202454/

And check out this thread: https://www.rx8club.com/series-i-tro...-plugs-234383/

Old ignition to new ignition was +27whp reclaimed, so your 30hp might be pretty accurate. So many owners really have zero idea of how a healthy RX-8 should feel until they get around to actually doing the regular maintenance.

 

I read somewhere about a " front and back spark plug", and to be carefully not to switch them?

 

2 plug types, one has an L in the part number, one has a T in the part number. These stand for Leading and Trailing, or an easy way to remember is Lower and Top. Another way is the big L and T stamped on the housings next to each plug hole. Swapping plugs between the holes is going to lead to lower power, misfires, and efficiency problems, but no inherent engine damage unless you try to keep them like that all the time.

The switching warning to make sure the wires aren't switched, as that could certainly lead to engine damage if the ECU fires 1 coil, thinking that it is going to be sparking a certain plug, but the wires are crossed and it sparks a different plug instead.

The order of the wires from the coils to the plugs:

 

Thank you, as usual, you people on this site are extremely helpful!

 

Yep, Replace Those Coils! I bought my 6-spd. RX-8 new in Nov. 2003 and have maintained it religiously ever since. She has just under 60,000 miles on the clock- I don’t drive it in our Ohio winters, but otherwise, the car gets used, and I don’t baby it. It has always started and run beautifully, and I have never enjoyed a car more.
However, I encountered a gremlin a couple of years ago... after driving for about an hour on a really hot summer day, it started to lose power and felt like I was running out of gas. I was low, so I found a station, filled up, and it ran fine. I NEVER got a check-engine light. I had my dealer check it, and there were no codes from a CEL, -but he found a lot of dirt in the cup around the fuel pump... we chalked it up to dirt, and he cleaned it after testing the fuel pump. She ran great after that.
-Until the following summer. Same exact situation: very hot day, longer drive, no power, barely running. After a cool-down, it was fine. Again- no light, no code. Internet searches showed that others have also experienced the same issue.
SO- when I went to replace the plugs & wires this Spring at 59,000 miles & 16.5 years, I did a ton of reading on any RX-8 message board I could find. I consistently found people who talked about coils being a weak spot, especially the original version, that they SHOULD be replaced, and that I was overdue. And- although weak or failing ignition coils CAN cause misfiring, a check-engine light, and other major problems, they might NOT. In fact, the car can seem to run fine, even though the spark may be getting weaker over the long haul, with any weakness being intermittent.

-Once I pulled the old coils out, sure enough, the appearance of the under side of all four showed that they had been overheating. As per all advice on best practices, I replaced them with new Mazda OEM coils with the updated number. Yes, Mazda has revised them. WELL- reports of noticeably improved power turned out to be true! I had read that you’ve lost horsepower that degraded gradually over the years, and the difference was absolutely amazing! I read an account where they tested a RX-8 before and after new coils, and the result was a measured gain of between 20 & 30 horses, and I believe it. My 8 seems to be a perfect example. In fact, about 40% of the time, my car has had a tendency to stumble slightly from a standstill. It’s been like this since brand new, and I always figured that I had a lousy feel for this clutch. Guess what. It’s over 16 years later, new coils, and no more stumble.

Many thanks to EVERYONE who has contributed information about ignition coils on RX-8 message boards over the years. Because of your input, my 8 has a new lease on life. So, yes- replace those things. The job is easier & quicker than it seems. I guess you don’t absolutely HAVE to remove the air box and the shock tower brace, but those things are a breeze and only take a few minutes to free up lots of room to work. Just remember that it’s very hard to remove the air filter box on a cool/cold day. Also- conventional wisdom says to buy Mazda coils instead of aftermarket, and I followed that advice. Just make sure they are the updated parts. Instructions on doing the job are all over the ‘Net... just search.