So i'm sure someone has heard or had this problem before, but let me sum it up in my situation. Ill try and make this simple,

Bought the car from Mazda dealership certified, had a few upgrades on in (intake, midpipe, cooling screens, and possibly BHR ignition kit? I say possibly becuase I dont know for sure, but it says MSD 8.5mm, they are red wire and they look identical to the BHR kits.

Anyway so just recently (random) if I would try and rev past 7k ish, it would give clear hesitation. Took it to dealership and they said ERROR CODE P0300 which translates to "Random Misfire" They said plugs need to be changed, I declined service and did it myself. Same issue.

Basically, I am stuck and dont know what to do now. I would rather not go back and spend money on diagnostics but may have to . It drives normal, only when you try and hit 7k is when it causes issues.

Any insight or help would be very much appreciated. Very well could be another post on this, I looked, but it didnt fully relate to my situation.

 

you will want to get an HEI spark tester from your local autoparts store and make sure all coils are in working order.

https://www.rx8club.com/series-i-do-...-wires-222641/

 

Hey - stupid question here but, is the car manual or automatic? I only ask because I don't see anything specific in the post that could distinguish one or the other.

From one of your other threads, a linked RX8 was manual. Could you confirm?

 

If it is an R3 then it has to be a manual...

What type of intake do you have? If it is an AEM/MS CAI then check to make sure the screens aren't sideways in the tube.

 

yes manual. And racing beat intake only mentioned because that's how I got it. Would it be best t just go to dealership and take hit on diagnostics or any ideas?

 

I gave you a really good / easy suggestion .....

 

Little update. Car seems very slow. Like Huge power loss not sure if that helps but definitely a decrease in power

 

I will try and get that by tonight . If a coil is bad, can you just replace the one or should you do a full swap? And can you used the coils autozone has or should you order better one if those aren't the best

 

Just want to throw this one out in the ring...OP @ what temperature (engine) are you trying to rev past @ 7000 RPM...you do know that until engine is fully warm (almost) there are two stages where the ECU/PCM will not allow you to rev past until engine reaches set temps.

In other words "if" you are trying to rev the engine when cold...it wont work.

You said you changed Spark Plugs, I take it as a given that you installed correct RX-8 spark plugs and the HT Leads in the correct firing order?, Leading and Trailing, Rotor 1 and Rotor 2?

If you believe you have BHR Coils talk to Charles who is the owner of BHR (PM him here), he may be able to identify coils and possible issue IF it is coils.

 

BTW, How many miles has your 09 done?

 

Hello, misfires sometimes cause catalytic converters to fail. Power loss at high rpm is classic symptom.
You can get free OBD scans from most parts stores.
Also be sure your wires are "snapped on", making good connection with your plugs.
Good luck.

 

Yes I probably should have clarified. Car just broke 50k. The engine is no question warm when I try and give it some power. I know the two cold stages and its not in either of them. I installed the NGK plugs, two trailing, two leading just how they were suppose to. I can re check connections, but I am sure that I made sure it was in place the first time. IN any case when they were replaced, the same exact issue happened. And would I even need an OBD scan if I know its random misfire? YOu mean just check on the code? The code is P0300. I know there is a sticky on it so I have looked there, just looking for some more specific information. I still am in my year certification, and have my 7 year 100k powertrain so everything in this list in the link attached I have covered, but the issue here is, If I bring it in and they notice the BHR is that going to cause some issues. They didnt say anything the first time, but who knows.

http://www.google.com/url?sa=t&rct=j...47244034,d.cGE

 

Have you reset the ECU?

 

If it requires disconnecting the battery, I am trying to avoid that, because I have Viper Security remote start on it, and thats going to need to be re-calibrated. WHen I did the plugs the check engine light was on so we used out scan tool and reset it that way if that is the same? But it came back on after a few minutes of driving

 

20 brake pedal stomp. This from memory, (+ good buzz=you should search) turn key on, stomp brake pedal 20 times within 8 seconds, turn key off, wait 30 seconds, turn key back on.
(I think)
SEARCH NOOB!
Ha! .
You're the first I ever said that to.
I'm a coupla rum & cokes in.
Good luck!

 

^ Wrong. that is for S1s only.

S2 requires a battery disconnect and then an immediate brake stomp (within 60 seconds). The nbattery reconnect.

 

Thank you for the correction.
I didn't know they were different.

 

Wasted a perfectly good "search noob"

 

did you ever get around to testing those coils? Not worth going on a witch hunt if you cannot even confirm that all the coils are in working order ...... not to mention that you will waste money at the dealership if thats what the cause is

 

No biggie, but in my defense, you did post a DIY Link for S1.
It figures that in all my years of doing auto work and investing in tools, the only tool I ever sold was my USA made timing light to the neighbor kid who was going to Vo-Tech.
I figured with newer ignitions I wouldn't need it anymore.
I wish I still had it.
In your opinion, are there pros & cons to HEI tester over timing light?
Thanks for not flaming me earlier.

 

Yep, got to agree with Paimon...Always start ignition first, however it could be any one of these for P0300....Random misfire detected (from Mazda)

DETECTION CONDITION

The PCM monitors the eccentric shaft position sensor input signal interval time.
The PCM calculates the change of the interval time for each rotor.
If the change of interval time exceeds the preprogrammed criteria, the PCM detects a misfire in the corresponding rotor. While the engine is running, the PCM counts the number of misfires that occurred at 200 eccentric shaft revolutions and 1,000 eccentric shaft revolutions and calculates the misfire ratio for each eccentric shaft revolution. If the ratio exceeds the preprogrammed criteria, the PCM determines that a misfire, which can damage the catalytic converter or affect emission performance, has occurred.

This is a continuous monitor (misfire).

The MIL illuminates if the PCM detects the misfire which affects emission performance in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.

The MIL flashes if the PCM detects the misfire which can damage the catalytic converter during the first drive cycle. Therefore, PENDING CODE is not available while the MIL flashes.

PENDING CODE is available if the PCM detects the misfire which affects emission performance during the first drive cycle.

FREEZE FRAME DATA (Mode 2/Mode 12) is available.

The DTC is stored in the PCM memory.

POSSIBLE CAUSE

Erratic signal to PCM

APP sensor signal malfunction (Accelerator Pedal)

ECT sensor signal malfunction (Coolant Temp Sensor)

MAF sensor signal malfunction

TP sensor signal malfunction (Throttle Position)

VSS signal malfunction (Vehicle Speed Sensor)

Eccentric shaft position sensor malfunction

Ignition system malfunction

High-tension lead malfunction

Incorrect power supply to ignition coil

Ignition coil malfunction

Spark plug malfunction

Excess air suction in intake-air system

MAF sensor malfunction

Fuel line pressure malfunction

Leakage fuel

Fuel pump unit malfunction

Pressure regulator (built-in fuel pump unit) malfunction

Insufficient compression

Metering oil pump malfunction

Engine oil condition malfunction

Increased oil pressure

Oil passage malfunction

Engine malfunction

Purge control system malfunction

Leakage engine coolant

PCM malfunction

I would also just add I see you said you have a Viper car alarm, these also 'can' give issues, however one would think since car is on and working it 'should' not be this.
IMO, unless your car is exposed in a bad area, why would you need an alarm, factory immo is failsafe, unless someone has your keys they cant drive your car.
Viper does not have a great reputation here.

 

Alright just an update. We went ahead and cleaned the MAF, tightened some bolts attached to intake (no idea why they were even loose) and reset the ECU into learning mode. Check engine went away, and then about 10 min later, came back on. Still trying to get around to getting coils tested to who ever suggested, just havent had that much time but should be today now that I have a break. Keep you posted.

 

You said you have a midpipe? So no catalytic converter? If not, I just had an issue on mine which I will post about in another thread that is similar.

I have an 09 R3, 48k miles and the cat was fully clogged and that was the issue. My car experienced random hesitation, to high RPM power loss, then to RPM walls decreasing daily. Eventually couldn't rev past 6k, and it was like I couldn't accelerate at all.

Replaced the Cat, fixed. Even got 2~3mpg more than I have for over 30000 miles with same driving style.

I will post videos too. Does it misfire if you hold it at WOT at 7k?

 

Is there any chance the problem could be caused by an intake plenum actuator that isn't actually *actuating* anymore? (yay alliteration!)

 

This did cross my mind too but VFAD opens @5500 RPM and doubles air intake flow.
I disconnected and capped the nipple years ago so it is always open.

Definitely worth a try as it 'may' not be opening at all so engine might be starving for fresh air @ 7000+ RPM.?
If OE connected the flap is always closed below 5500 RPM when engine is running.