A Shuddery Mystery No-one Seems to be Able to Solve
10-24-2022, 07:10 PM
#1
A Shuddery Mystery No-one Seems to be Able to Solve
Hi All,
An issue I had thought resolved has not been resolved despite Mazda techs being unable to recreate (and therefore experience and diagnose) the issue. Series II black manual RX-8.
For background, I am the author of this thread: https://www.rx8club.com/new-member-f...timing-274352/ - If you read that you will see the background to the issue and I am sad to say that it has not been resolved as the car did the same thing this morning, albeit in a watered down version.
The car has done no long trips since last service (and the above post - both 2 weeks ago) and has in that time only done short trips of 3-5 kms once every couple of days and without any issues ... until this morning.
Early this morning I started her up - no issue - driving in 1st gear out of the car park in our building and essentially the engine is still warming up - still slightly higher revs in neutral. As I leave the building, she starts shuddering again (as per above post) and misfiring, and limps down the street. I give her some more juice and the issue eases and she drives Ok (although only going about 200m - just to get her washed/detailed as usual at the other end of the building). CEL does not come on at this point.
Pick her up 45 mins later post detail, and as I am parking her, she is shuddering and CEL is flashing. No ACS light but the CEL is flashing. Giving her juice eases the shuddering once but only for a few seconds and after that she just keeps shuddering and misfiring and more juice no longer smoothes her out ... now she just shudders with more revs and once again (see earlier post) has very little power.
Very frustrating that the Mazda techs after 3-4 days and 70kms of driving can't recreate the issue and yet happens for me twice in the same morning.
Mazda techs told me that when they were checking her out, despite (see earlier post) both the CEL flashing and ACS staying lit last time, they apparently threw no codes (didn't think that was possible without battery disconnect and there was none of that but they swear black and blue no codes were there) ... but now that I had a flashing CEL again (although no ACS light this time) I will assume a code has been thrown ... so maybe I don't take it to Mazda this time and maybe try to get RACQ out (preferably a rotary specialist) to at least check the codes?
So do I then ask Mazda to quote me on an entire engine deconstruct and reconstruct? I think it's worth paying the $$ that might cost in labour instead of just hoping that nothing happens on the road???
A bit lost here ... can anyone help???
An issue I had thought resolved has not been resolved despite Mazda techs being unable to recreate (and therefore experience and diagnose) the issue. Series II black manual RX-8.
For background, I am the author of this thread: https://www.rx8club.com/new-member-f...timing-274352/ - If you read that you will see the background to the issue and I am sad to say that it has not been resolved as the car did the same thing this morning, albeit in a watered down version.
The car has done no long trips since last service (and the above post - both 2 weeks ago) and has in that time only done short trips of 3-5 kms once every couple of days and without any issues ... until this morning.
Early this morning I started her up - no issue - driving in 1st gear out of the car park in our building and essentially the engine is still warming up - still slightly higher revs in neutral. As I leave the building, she starts shuddering again (as per above post) and misfiring, and limps down the street. I give her some more juice and the issue eases and she drives Ok (although only going about 200m - just to get her washed/detailed as usual at the other end of the building). CEL does not come on at this point.
Pick her up 45 mins later post detail, and as I am parking her, she is shuddering and CEL is flashing. No ACS light but the CEL is flashing. Giving her juice eases the shuddering once but only for a few seconds and after that she just keeps shuddering and misfiring and more juice no longer smoothes her out ... now she just shudders with more revs and once again (see earlier post) has very little power.
Very frustrating that the Mazda techs after 3-4 days and 70kms of driving can't recreate the issue and yet happens for me twice in the same morning.
Mazda techs told me that when they were checking her out, despite (see earlier post) both the CEL flashing and ACS staying lit last time, they apparently threw no codes (didn't think that was possible without battery disconnect and there was none of that but they swear black and blue no codes were there) ... but now that I had a flashing CEL again (although no ACS light this time) I will assume a code has been thrown ... so maybe I don't take it to Mazda this time and maybe try to get RACQ out (preferably a rotary specialist) to at least check the codes?
So do I then ask Mazda to quote me on an entire engine deconstruct and reconstruct? I think it's worth paying the $$ that might cost in labour instead of just hoping that nothing happens on the road???
A bit lost here ... can anyone help???
Last edited by scottybmc; 10-24-2022 at 07:12 PM.
10-24-2022, 09:05 PM
#2
Can you note any other variables that might be in play?
Was the fuel level the same both times this happened?
Did the tachometer continue to read normally or jump around?
Is there oil in the intake tract?
Have the ignition coils been replaced in the last 30k?
Mazda won't take apart the engine, they're not allowed to. They can replace it with a fresh one, but that's an expensive way to find out that wasn't the problem. You can have a compression test done to make sure, but nothing here says "compression loss".
Was the fuel level the same both times this happened?
Did the tachometer continue to read normally or jump around?
Is there oil in the intake tract?
Have the ignition coils been replaced in the last 30k?
Mazda won't take apart the engine, they're not allowed to. They can replace it with a fresh one, but that's an expensive way to find out that wasn't the problem. You can have a compression test done to make sure, but nothing here says "compression loss".
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scottybmc (10-24-2022)
10-24-2022, 10:47 PM
#3
Hi Loki,
Fuel level was around the same in both incidents (about a quarter of a tank).
Tacho didn't seem to be playing up - didn't notice any jumpiness.
I couldn't tell you whether there is any oil in the intake tract?
Ignition coils were replaced around 20k ago.
Fuel level was around the same in both incidents (about a quarter of a tank).
Tacho didn't seem to be playing up - didn't notice any jumpiness.
I couldn't tell you whether there is any oil in the intake tract?
Ignition coils were replaced around 20k ago.
10-24-2022, 11:09 PM
#4
If you pull the air filter, you should see oil on it if some has made it to the air tract.
Fuel being low in both cases could be a clue. Does it drive fine with thay fuel level otherwise? There are a few things in play there: the siphon transfer from one side of the tank to the other (fuel is only sent to the engine from one side), the fuel level sensor itself could be lying, the fuel pump could be on its way out (although this is a bit unlikely given that it didn't really have time to heat up in your cases). Normally the fuel pump is cooled by fuel, but if the fuel is low, and the pump is borderline, it can act up.
Was your year of rx8 subject to the fuel pump housing and /or fuel tank padding recall/tsb? Has anyone fooled around in the tank for any reason?
Fuel being low in both cases could be a clue. Does it drive fine with thay fuel level otherwise? There are a few things in play there: the siphon transfer from one side of the tank to the other (fuel is only sent to the engine from one side), the fuel level sensor itself could be lying, the fuel pump could be on its way out (although this is a bit unlikely given that it didn't really have time to heat up in your cases). Normally the fuel pump is cooled by fuel, but if the fuel is low, and the pump is borderline, it can act up.
Was your year of rx8 subject to the fuel pump housing and /or fuel tank padding recall/tsb? Has anyone fooled around in the tank for any reason?
10-25-2022, 12:16 AM
#5
Master of 9k Downshift
Really seems like an electrical or ignition system issue. Flashing CEL is always misfire and shuddering signifies inconsistent power making in the engine. Have ignition coils been replaced recently, spark plugs, and wires? I assume the car starts without any trouble cold and hot so there shouldn’t be a compression issue?
I’ll just say that I am done with dealership service. My car lost power in high RPM ranges. I asked them to check the catalytic converter specifically and they refused, because there weren’t any codes. I finally got another look from another RX8 owner and he confirmed catalytic converter and then I replaced myself with BHR midpipe. Car runs great now.
Not saying this is your problem (and I doubt it is), but if you can find another owner in your area to help you out you’ll probably have a lot more success. Dealerships don’t want to deal with these cars anymore.
I’ll just say that I am done with dealership service. My car lost power in high RPM ranges. I asked them to check the catalytic converter specifically and they refused, because there weren’t any codes. I finally got another look from another RX8 owner and he confirmed catalytic converter and then I replaced myself with BHR midpipe. Car runs great now.
Not saying this is your problem (and I doubt it is), but if you can find another owner in your area to help you out you’ll probably have a lot more success. Dealerships don’t want to deal with these cars anymore.
Last edited by schm1347; 10-25-2022 at 12:19 AM.
10-25-2022, 07:42 AM
#6
You gonna eat that?
iTrader: (1)
I agree with a lot of the previous posts, fuel pump, electrical or cat are good possibilities.
I didn't read your previous thread.
Did you ever have the cat replaced?
A bad cat should throw a CEL, but a piece of old cat stuck in the cat back exhaust might not.
Most dealerships are only out to make easy money, imo.
If it's not something they deal with on a regular basis they probably don't want to waste time troubleshooting when they can be making money on other more easily repairable jobs.
Changing parts on traditional piston engines is more profitable than having one or more techs spending who knows how much time trying to figure out any one of myriad RX8 issues that can cause your symptoms.
You can bring it to a reputable local auto shop to diagnose issues common to most cars.
Fuel pump pressure, electrical diagnosis for something as simple as loose or corroded ground wires, and checking the cat.
I recently had problems with squirrel chewed wire harnesses that a local shop fixed for me.
Many local parts stores now scan the OBD for free, try that first, then find a reputable shop to see if they can figure it out.
I didn't read your previous thread.
Did you ever have the cat replaced?
A bad cat should throw a CEL, but a piece of old cat stuck in the cat back exhaust might not.
Most dealerships are only out to make easy money, imo.
If it's not something they deal with on a regular basis they probably don't want to waste time troubleshooting when they can be making money on other more easily repairable jobs.
Changing parts on traditional piston engines is more profitable than having one or more techs spending who knows how much time trying to figure out any one of myriad RX8 issues that can cause your symptoms.
You can bring it to a reputable local auto shop to diagnose issues common to most cars.
Fuel pump pressure, electrical diagnosis for something as simple as loose or corroded ground wires, and checking the cat.
I recently had problems with squirrel chewed wire harnesses that a local shop fixed for me.
Many local parts stores now scan the OBD for free, try that first, then find a reputable shop to see if they can figure it out.
10-25-2022, 10:51 AM
#7
Master of 9k Downshift
I will say my car never ever threw a CEL for the catalytic converter, one lean mixture code was all. Front section was in pieces (aka marbled in the exhaust) and rear section was clearly clogged which became much more evident once I pulled off and looked at it myself. I will say that mine didn’t misfire until pushing higher RPMs.
Easy way to check catalytic converter is to buy a cheap $20 O2 socket set and a $40 endoscope and fish it in through O2 sensor hole and have a look around.
To have your car have so much trouble at low RPMs would imply an extremely clogged catalytic converter, but it’s possible.
Second BigCajun. Have another non-dealer shop just run through the electrical systems and fuel pressure. Another thing to do is to clean the Mass Air Flow sensor. It’s super easy and can be done in 5 minutes and a few bucks for the cleaner. For more ideas you can look up “RX8Help Misfires” on Google or here.
Everything is all the same as other cars. People get intimidated by these cars way too easily and the only real difference is the engine along with required oil meter pump. Air intake, fuel, spark, exhaust, compression. The first 4 are the same as any other car. The last one is unique to rotaries.
Easy way to check catalytic converter is to buy a cheap $20 O2 socket set and a $40 endoscope and fish it in through O2 sensor hole and have a look around.
To have your car have so much trouble at low RPMs would imply an extremely clogged catalytic converter, but it’s possible.
Second BigCajun. Have another non-dealer shop just run through the electrical systems and fuel pressure. Another thing to do is to clean the Mass Air Flow sensor. It’s super easy and can be done in 5 minutes and a few bucks for the cleaner. For more ideas you can look up “RX8Help Misfires” on Google or here.
Everything is all the same as other cars. People get intimidated by these cars way too easily and the only real difference is the engine along with required oil meter pump. Air intake, fuel, spark, exhaust, compression. The first 4 are the same as any other car. The last one is unique to rotaries.
Last edited by schm1347; 10-25-2022 at 10:59 AM.
12-21-2022, 12:49 AM
#8
Shuddery Mystery Solved
Hi All,
So, that shuddery mystery I posted here about has been resolved, by an excellent rotary mechanic I should say and to whom I will be sending my RX-8 from now on.
Anti-climactically, and despite the symptoms that might have lead elsewhere, it was simply the coils - replaced them and all good. No cat issue in sight.
So, that shuddery mystery I posted here about has been resolved, by an excellent rotary mechanic I should say and to whom I will be sending my RX-8 from now on.
Anti-climactically, and despite the symptoms that might have lead elsewhere, it was simply the coils - replaced them and all good. No cat issue in sight.
12-21-2022, 05:50 AM
#9
RX-Heaven
iTrader: (6)
Glad to hear that the issue was solved. Often times coils will show signs of failure as they warm up and this seems to fit the bill in your case. I've also heard mixed things about using aftermarket coils as well. Seems most guys prefer the Mazda coils. I have the BHR coil setup in my Brilliant Black 04 and it has been flawless since I purchased the car in 2015. The coils were installed by the previous owner in 2012.
12-21-2022, 06:58 AM
#10
Master of 9k Downshift
Hi All,
So, that shuddery mystery I posted here about has been resolved, by an excellent rotary mechanic I should say and to whom I will be sending my RX-8 from now on.
Anti-climactically, and despite the symptoms that might have lead elsewhere, it was simply the coils - replaced them and all good. No cat issue in sight.
So, that shuddery mystery I posted here about has been resolved, by an excellent rotary mechanic I should say and to whom I will be sending my RX-8 from now on.
Anti-climactically, and despite the symptoms that might have lead elsewhere, it was simply the coils - replaced them and all good. No cat issue in sight.
12-23-2022, 11:34 AM
#11
Grand Chancellor
Ignition system chain was my first thought. Surprised it took so long to arrive to this conclusion. Most non-turbo rotary engine issues revolve mainly around ignition system and lack of oil care.
Now go enjoy the car.
Now go enjoy the car.
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