Hey all, new rx8 owner from kansas, just purchased it last Sunday, 05 rx8 with a "rebuilt" engine. 150k on the chassis and 3k on the motor.

It definitely has issues 😂
Buy it runs and drives.

Known issues - cylinder 1 misfire (at idle).
Power steering out (cleaned the plugs no help)
Trash coilovers (raceland ugh)
All the warning lights 😂
Some electrical gremlins (dome light comes on when I hit bumps, heated seats don't work ect ect)
Member of the big **** gang... 😂

Pros motor feels strong, ( no compression test yet so idk)
Hks exhaust
Body is mostly straight (paint is obviously poor but no rust)
New clutch
Close proximity to prather Motorsports 😂

Excited to learn from people who have more experience with rotary engines and the rx8 chassis.

(Picture from sellers ad, haven't taken any yet)

 

Misfire is usually ignition related. If you don't know when it was last done plugs coils and wires are a good idea. There's also aftermarket coils that last much longer than oem. Cleaning the ess and maf and also a good start along with getting any fault codes. Does it have a cat?

 

Where at in Kansas?

 

Yeah plugs supposedly were changed, but not coils so I'm looking into the best option on them currently, just the code for the random misfire, upstream 02 sensor heating element currently.

Was told it had a car delete... But its sitting to low to tell without getting it in the air, which I will be doing later today. When I change the oil... Previous owner was running 5w20 but I want to move up to a 10w30. Planned to pull the intake off and clean the MAF as well today

 

Im From Topeka

 

Since this forum is kind of dead and I'm pretty much reading the whole internet on RX-8s right now, I'm just going to forum fairy until the mods stop me. I'm a pretty good backyard mechanic, so I shouldn't point you too wrong.

I hope you got that thing cheap af my friend . I love a big project though, so I would never say reconsider. From everything I've learned about RX-8s, under all the fuss is still the same solid car with an engine that can be pretty much infinitely rebuilt for relatively cheap.

So starting with the misfire, I'm not gonna come in and be mr know it all my first day here, but technically you have chambers or whatever the cool word is, not cylinders. I mean they're vaguely cylindrical, but they're like clover shaped chambers between the plates that the rotors spin around in. I'm not saying it to be ****, just to make sure we're on the same page of what the spark plug is going into. Besides that distinction, the basics of air, fuel, spark apply like any engine. My dad would go on some rant about taking everything out and bench testing it with a meter, but there are easier ways to test all of them. Your air flow sensors will tell you if you are getting air, so if you aren't you will have codes related to air/fuel mix. You can just take a fuel injector out of the hole while still connected to fuel, turn the car to acc position and let the pump pressurize. If fuel comes out of the injector, you have a working pump, injector and a line that at least flows enough to turn over the engine a bit. Finally spark you can test various points around the engine with a meter and then remove and bench test just the plugs to make sure they work. All of this stuff can be done by anyone with the help of youtube, basic tools and a multimeter in an afternoon. A mechanic can do all of it in less than an hour. If they take much longer they are getting high.

As far as all of your other issues combined, I would check all of your electrical relays, the battery terminals and every electrical connection you can find before you throw any effort at specifics. All of those are things that can be caused by electrical issues. I mean besides the spoiler, you have to unbolt that lol.

If you're not an electrician, it's time to go get a multimeter and devote your life to it for a week or two.

 

Focusing on the misfire would be what I would attack first. Pull the spark plus and inspect them. I would not take anyone's word for it that they were replaced. I change mine every 7k miles and the carbon deposits are heavier than on any of my RX-7's. I have bought RX-8's that have had the incorrect spark plugs installed. I have had some with all of the same plug. Check them, check your spark plug wires visually and with a resistance check if you want to go that far. Next, I would inspect the coils. They are prone to wearing out and should be replaced if the service history is unknown or if you see a light colored spot on the flat portion of the coil. I have a BHR coil set on my Brilliant Black car and it has eliminated the need for coil replacements by interval. Many misfire issues on these cars are ignition related. I would start there. Also, I would recommend performing a proper compression test with a rotary compression tester. Just to get a baseline of your engine's health. Not that you are using that to diagnose issues at this point, but its good information to have.

The heating element in the O2 sensor can be just that, a bad heating element. You can confirm by looking at the voltage on a live data readout using a scan tool. Also get the car in the air and inspect the oxygen sensor wires. Ensure none are cut or frayed or have missing insulation. Inspect the connector to ensure the pins are clean and that both connector bodies are secure together. Worst case, it needs and oxygen sensor.

What codes are you getting for the rack? What did you clean to try and solve the issue? Did you clean the ground points and run a tap down the thread of the ground point on the support bar? The grounds are completed through the threads of the bolt, so having clean bolt and captive nut threads are a must. Did you clean the contacts on the torque sensor and drive motor as well or just the harness?

Other than that, how does the car run and drive? Is the interior in good shape?

 

Lucky for me this is just a toy so I'm not in a rush and I'm going through many of the steps you have described already.

The current plan is to replace the spark plugs, and coils regardless of any testing because they are an unknown.

No code for the power steering on my code reader, I cleaned the two main plugs near the radiator using a dielectric spray, but have not cleaned any of the grounds yet.

The o2 sensor from visual in inspection appears to be fairly old, most likely original and will be replaced as well

The biggest issue I have found was the significant leak from the oil pan, pulled the pan last night cleaned and reinstalled found 2 bolt holes that were stripped and will need a helicoil kit.

Project cars are fun like this always something new to fix .

Compression test will have to wait until I find someone with a tester local unfortunately.

 

I think you should do yourself a favour and spend the money on a compression tester and not new coils and plugs.
At least then you will know whether the engine needs a rebuild.
Plugs and coils for the RX8 are fairly expensive, don't buy the cheap ebay coils.

 

I have to second this 1000%. Throwing parts at a car is the least efficient way to fix it. And due to what the plug goes into like I was rambling about, your risk isn't blasting the plug back out, but rather an engine implosion. That's worst case scenario, but it can be so many things. Spark plugs are the easiest part in a car to bench test. Testing all your electrical and your compression is the first thing you should do to save time and money.

I know I'm rambly and not the best at explaining, but the explode part is a legitimate concern. A piston engine has a head, so if the fuel and spark are going in at the wrong part of the stroke, you either get fuel up in your coil and get misfiring. Or in the worst case it explodes in the head and usually breaks the threads on the plugs, the weakest link, shooting them out into the engine compartment. On a rotary, if you are injecting into the next apex, instead of into an open chamber about to be squished by the rotor, the unburnt fuel from one chamber will meet the still flaming fuel from the other in at the ports and explode the engine.

 

While yes throwing parts at a car is not a great way to do anything, but testing that it was the coils was so stupid easy that it took me less than 10 mins.

Swapping the coils from rotor 1 to rotor 2 and seeing if the misfire was then on rotor 2 (it was) was easier than waiting for a compression tester to come in and still not give me any info on the misfire.

While I will eventually buy a rotary compression tester, it's just not on the top of the list ATM.

 

It's too bad Topeka is about 200 miles from me. I have a compression tester (that I still haven't used) and an S1 steering rack that you could use for testing.

 

Did you find that the misfire moved from the front rotor to the rear when swapping the coils? Have you pulled the spark plugs yet to check their condition? I was wondering if you had made any progress on the car recently. If you find that the coils need replaced, consider something like the Black Halo Racing coil set if you are wanting longevity. OEM Mazda coils will also last for some time and work perfectly well. Maybe compare pricing and see which works best for you.

 

Yes swapping the coils moved the misfire to rotor 2.

Replaced the coils and it runs excellent now.

Still needs work on the steering issue but its only a minor pita to drive it as is 😂

 

Glad to hear the ignition issue was solved easily. Its typically just plugs and coils. The wires seem to hold up pretty well until they get oil spilled on them and soften up. Did you end up replacing the spark plugs as well?

 

Welcome to the club, yeah the forums are rather dead recently. People just are not as active as before. Online forums in general are kinda dying out since we have facebook groups or discord groups taking over. Which kinda sucks since you wont be able to google search those groups in the future.

It is fairly typical that the older ignition coils fail after about 30-40k miles. Updating to the mazda RevC coils is the ideal solution for a street car (if you got new genuine mazda coils this is likely what you got). People may still push the LS coil and IGN1a coil kits, but IMO they are just a pointless expensive swap that is certainly not reliable. The LS coils are not designed around firing this fast, but they do the job. The IGN1a coils are just prone to melting if you have anything wrong with the car or tune, however they do have the most spark energy when functioning.

The front O2 is important since that is how your ECU controls the engine. The rear O2 is just an emissions check to see if your Cat is still in the car.

For the Power steering the first thing to always check is make sure all your contact points are clean. Especially all of the grounds which tend to rust. My dumbass had painted the engine bay and covered the grounds in one of my cars. I also highly recommend buying a couple feet of tubing and extending the coolant reservoir cap relief dump somewhere under the car so it does not keep draining onto your connectors. Do the Key on, all the way left, all the way right, endstop reset. If there are issues after this then its either the rack or the module. Both of which become Ebay gambles whether you buy a working one or not, so I caution buying from small ebay sellers and suggest sticking with bigger junkyard sellers that depend on their relationship with ebay. At 150k miles you might want to get a new Steering U joint if you drive without power steering a lot. Both my cars at that mileage that lost power steering ended up breaking the joint after a couple thousand miles. Or just replace it with the new rack if the time comes.