New and Need HELP! Diagnose my RX8
05-11-2014, 03:21 PM
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New and Need HELP! Diagnose my RX8
Hello all! I've been lurking on the forum since I purchased my RX8 and it's been a great help doing minor maintenance for it! I'm hoping you can help me out with what seems to be a bigger problem.
Patient Profile:
2008 Mazda RX-8
Automatic transmission
Approx 72k miles.
Purchased as second owner around 60k miles.
Per CARFAX- All maintenance performed at John Hine Mazda in San Diego and I ASSUME they did everything the vehicle requires at the normal intervals. (Dangerous assumption I know.
Symptoms
Vehicle starts rough. Takes a few seconds to turn over. Idles rough and accelerates rough at low rpms. There is a clear vibration and hesitation when setting off in first gear up to probably 3k rpms. There is also a noticeable power loss at low rpms and the car seems to be struggling to determine what gear it should be in when I am going uphill. (Commute everyday on the 67)
*+*+*+*+*+
I'm wondering what some likely causes of this problem are. So far I'm suspecting ignition coils but would appreciate forum opinion. Trying to figure this out today so I can order any necessary parts and fix the problem on Wednesday.
Patient Profile:
2008 Mazda RX-8
Automatic transmission
Approx 72k miles.
Purchased as second owner around 60k miles.
Per CARFAX- All maintenance performed at John Hine Mazda in San Diego and I ASSUME they did everything the vehicle requires at the normal intervals. (Dangerous assumption I know.
Symptoms
Vehicle starts rough. Takes a few seconds to turn over. Idles rough and accelerates rough at low rpms. There is a clear vibration and hesitation when setting off in first gear up to probably 3k rpms. There is also a noticeable power loss at low rpms and the car seems to be struggling to determine what gear it should be in when I am going uphill. (Commute everyday on the 67)
*+*+*+*+*+
I'm wondering what some likely causes of this problem are. So far I'm suspecting ignition coils but would appreciate forum opinion. Trying to figure this out today so I can order any necessary parts and fix the problem on Wednesday.
05-11-2014, 04:11 PM
#2
I'm listing all POSSIBLE options, obviously some of them are more rare and/or harder to check for so always for easier/more common. Also I found ALL of this just by searching, try and do the same. May have a couple questions but lets get to work.
1) First is does it FEEL rough or does the RPM gauge actually fluctuate? If it isn't moving, then don't worry about it, it feeling a little rough is normal. IF it is moving, couple options it could be:
Ignition system (coils, wires, plugs)
PCM flash M (don't have much info about this one).
Oil level
Motor mounts and how to check :
2) For the car waiting to turn over, could also be ignition, most likely ignition.
3) Now onto the low power:
Throttle sensor
Again, ignition system
throttle body sensor
Vacuum leak
Catalytic Converter, although possibility is minimal
Primary intake
MAF
SSV
4) Hesitation I only have two options, couldn't find much information:
Fuel Lines
Fuel Pump
1) First is does it FEEL rough or does the RPM gauge actually fluctuate? If it isn't moving, then don't worry about it, it feeling a little rough is normal. IF it is moving, couple options it could be:
Ignition system (coils, wires, plugs)
PCM flash M (don't have much info about this one).
Oil level
Motor mounts and how to check :
- On manual transmission vehicles, when decelerating in 3rd gear with engine speed less than 3,000 RPM at approximately 30 MPH (50km/h), then quickly depressing the accelerator pedal again, a hesitation may occur. This symptom can only be observed in this engine speed and vehicle speed range.
3) Now onto the low power:
Throttle sensor
Again, ignition system
throttle body sensor
Vacuum leak
Catalytic Converter, although possibility is minimal
Primary intake
MAF
SSV
4) Hesitation I only have two options, couldn't find much information:
Fuel Lines
Fuel Pump
05-11-2014, 05:58 PM
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In this case, replace the coils, plugs and wires. All symptoms fit ignition failure, and while you could have other problems, if you don't know the age of the parts you can assume that they were never changed, and you need to change them as part of maintenance anyway. Most people here won't give you any other diagnosis as long as the ignition remains unchanged and unknown. They are CRITICAL to a well performing engine.
Even if the ignition isn't actively causing misfires or rough idle or hesitations, it's been dyno proven that 30,000 mile stock ignition is down ~30whp from brand new ignition, all else being equal. People complain that the 8 isn't fast enough, but are leaving 1/7th of their power on the table for no good reason.
05-11-2014, 08:00 PM
#4
A deadly assumption for an RX-8, because the dealer's maintenance list doesn't even address half of the engine damaging or otherwise dangerous-to-ignore maintenance items.
In this case, replace the coils, plugs and wires. All symptoms fit ignition failure, and while you could have other problems, if you don't know the age of the parts you can assume that they were never changed, and you need to change them as part of maintenance anyway. Most people here won't give you any other diagnosis as long as the ignition remains unchanged and unknown. They are CRITICAL to a well performing engine.
Even if the ignition isn't actively causing misfires or rough idle or hesitations, it's been dyno proven that 30,000 mile stock ignition is down ~30whp from brand new ignition, all else being equal. People complain that the 8 isn't fast enough, but are leaving 1/7th of their power on the table for no good reason.
In this case, replace the coils, plugs and wires. All symptoms fit ignition failure, and while you could have other problems, if you don't know the age of the parts you can assume that they were never changed, and you need to change them as part of maintenance anyway. Most people here won't give you any other diagnosis as long as the ignition remains unchanged and unknown. They are CRITICAL to a well performing engine.
Even if the ignition isn't actively causing misfires or rough idle or hesitations, it's been dyno proven that 30,000 mile stock ignition is down ~30whp from brand new ignition, all else being equal. People complain that the 8 isn't fast enough, but are leaving 1/7th of their power on the table for no good reason.
Agreed though, almost all of the symptoms point towards ignition, should clear most if not all problems.
05-11-2014, 08:03 PM
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Here is the back to back dyno tests done on old vs new OEM ignition, in case you were interested in reading about it.
https://www.rx8club.com/series-i-tro...-plugs-234383/
https://www.rx8club.com/series-i-tro...-plugs-234383/
05-14-2014, 07:34 AM
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I only joined this site today and only have had my 2007 Rx8 an year now,I had similar issues and I only removed and cleaned the Mass airflow sensor as it was very dirty, the results very unbelievable! Like A new Car! Only if I can figure out my issue ,lol,,,Engine stall with excessive braking/clutch depression (combined with excessive speed),,,,,,, with that said if I am using cruise control and depress the clutch,,,stalls 50% the time....I know I have to get it diagnosed but just trying to get an idea before dumping money into a Mazda service center because they don't seem to familiar with the RX8 in ST Johns ,Newfoundland. It mite be less expensive to have to invest in a Diagnostic tool myself after some research.
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