Navskhangura

Hi all,

I have owned my RX8 for around 18 months, first time owner. Not much of a hands-on guy but try my best, great guides on these forums etc.

My car is all stock, not mods or add-ons - 2008 231 model (I am based in the UK) - usual servicing and keep the oil topped up regularly. Not had many issues before but below is my issue:

Moved off from the traffic lights with no issues, put it into second and stepped on the gas and noticed it was unresponsive, I quickly tried to put it into second again (in case I selected 4th or something stupid like 6th) but again no response. Managed to pull over on the side and the car was juddering and struggling big time.

I managed to get the car started again pretty easily - it's never had issues starting hot or cold. But the car was driving REALLY rough. Could barely get above 30Mph and any time I let my foot off the gas it would cut out, just wouldn't hold idle. So I limped the car home, juddering and struggling, when I got home I could see the cat was glowing red. Once it cooled down I tried to get the cat off but broke a couple of tools in the process - so ordered an aftermarket cat and booked it into the local garage.

I also decided to change my plugs, coils and leads - after watching the tutorials I managed to do this myself. I assumed that the coils, plugs or leads had probably caused the cat to get blocked and the engine was struggling due to that reason. I don't know when they were last changed but I had done closed to 15,000 miles in the 18 months so gave it a go. When I removed the coils I could see each of them had the white round circle underneath.

Managed to get the cat swapped out for a new one but the garage said it still had the same issue. They assumed the back exhaust had got blocked from the insides of the previous cat. So we changed that too. Tried again and the car is still struggling massively.

Double checked all of my coils, plugs etc and they are all wired up correctly. Mechanic checked all the plugs and they're all looking good - getting a charge. I have tried a few other things like checking the airbox and cleaning the MAF sensor but it's still stuck in a state where it barely holds idle, feels really rough the car whole is basically shaking and juddering - the cat is glowing red when the car is on for more than 2 mins so I am just not driving it at all.

No idea what to check next but it's almost like the engine is misfiring somewhere and possible only one rotor is working. Fuel seems to be getting down to the cat and seems to be burning there - nothing should be blocked but combustion looks like it is happening in the wrong place. I haven't had a compression test but it will be really difficult to even get this done given the state of the car and the cat starting to glow so quickly.

Any ideas would be much appreciated!

Thanks!

BigCajun

iTrader: (1)

Are you getting any CELs?
Did the garage scan the OBD?
Did you get an OEM cat, or a cheaper aftermarket?
I'd suspect fuel pump or massive vacuum leak to start.

Navskhangura

Thanks for the prompt response BigCajun.

The CEL seems to come on and off - the initial problem it was flashing but hasn't flashed since - just comes on and off randomly. It wasn't on when I took it to the garage - I really should have asked them to scan the OBD.

Cheaper aftermarket cat.

I'll start doing some research on the fuel pump and vacuum leak - I remember seeing that vacuum leaks are a huge pain to check!

sonicsdaman

iTrader: (3)

flashing CEL is always a misfire, start with ignition components spark plugs, wires, and coils.
the air and fuel.

also inspect the cat, misfires let alot of unburned full out to the cat which in time can clog up and then kill the engine

Navskhangura

Thanks Sonicsdaman. I started with the spark plugs, wires and coils and managed to change them myself. Didn't drive the car apart from 1 mile down to the garage to get my new cat put on. Same issue so garage suggested changing the back exhaust in case it was blocked. The old cat was destroyed with bits missing when they took it off so hoped the back exhaust would sort it.

Apparently not. Same issue still occuring and new cat is glowing red each time I start it. I'm just not starting it or driving it, just waiting to find another potential solution.

Will check the fuel pump and vacuum leak.

Any other ideas? Could it be one of the rotors? I'm just wondering why it's so low on power, shaking and juddering like crazy and fuel is probably getting burnt in the cat...

Thanks!

sonicsdaman

iTrader: (3)

a glowing cat is a clogged cat

Navskhangura

I would normally agree, but we just put a new one on it. It was glowing at the garage when they started it up with the new cat on. I would be surprised if it got blocked from starting the car up the first time..

Something else is happening - like the fuel isn't being burnt in the engine but getting down to the cat and being burnt there. hence the glowing red. I might be completely wrong but it doesn't make sense that the new cat would be blocked 5 mins after putting it on.

Thanks!

dannobre

iTrader: (3)

Compression test...... that is always a good place to start with a rotary. Even if you pull the leading plugs and turn it over with a normal compression tester it is better than nothing.



If you are getting poor compression it wont fire...and the fuel will dump into the CAT and burn there like a torch

Jedi54

iTrader: (7)

just a few quick thoughts.

• flashing CEL usually points to a misfire which typically is ignition related. (I see you addressed that already)
• beware of cheap aftermarket cats. The truth is most can't handle the firebreather that is our little Renesis Motor and they burn up quite quickly and you're back to square 1
• white spots on the bottom of coils do not actually mean anything. For years we believed it was a sign of burnt up coils, that's since been disproven.

shaking / juddering is most likely ignition or fuel related.

• I know you double checked it but triple check to make sure the plug wires are going to the correct spark plugs. (that your trailing and leading didn't somehow get mixed up)
• do you have a timing light? you can attach them to the spark plug wires just to make sure you don't have a bad wire somewhere.
• You could always have your mechanic check the fuel pressure to see if it's low.
• if the new cat is glowing already just at idle, that could be a problem. Any chance you have a spare cat to test? If the one that was on there (I assume that was OEM)is indeed clogged (broken pieces of honeycomb) you could just take a prybar to it and hollow it out. That would allow you to eliminate a clogged cat as a possible cause of the issue. Just make sure it's actually broken already before destroying what is typically a very expensive OEM part.
  
• lastly, it could be time for a compression test. If you go this route, make sure they use an actual rotary engine compression tester.

Navskhangura

Thanks Dannobre. One of my initial fears, have been contemplating getting it booked in for a compression test - getting it there will be difficult though.

I will try to take the new cat off and see if its now ruined - could well be with it glowing a few times. Still - seems like an issue upstream to the cat but can't be certain.

Navskhangura

Thanks Jedi54. I will triple check the cables, plugs and coils tomorrow, I was starting to doubt myself but no harm in checking again.

I don't have a timing light but the mechanic did say he checked and there didn't seem to be anything wrong there - maybe he didn't check thoroughly enough.

I don't have a spare cat but the garage might still have the old one - I'll give them a call tomorrow and see if I can pick it up. I'll check it's fully broken and then gut it and put it back on - see if it makes any difference.

Thoughts on checking the fuel pump and vacuum leak? Tempted to try checking those regardless - I seem to have done a few bit so why stop?

Thanks!

BigCajun

iTrader: (1)

You may not have melted the cat, but I wouldn't plan on leaving it on long-term.
If you need it for inspections and such, I'd suggest you take it off now and save it.
Hollow out your old one for the time being as Jedi said and use it for a midpipe until you get sorted out.

Jedi54

iTrader: (7)

should be relatively easy for your mechanic to put a gauage on the pump and test fuel pressure.
vacuum testing is also relatively easy.
it would have to be a pretty big vaccuum leak to cause that level of shuddering though. (not saying it's impossible)

side note: what are the emission laws in UK. Do you have an inspection or a smog test of some sort you have to pass? Just trying to see if you'd need an OEM catalytic converter down the road

Navskhangura

Thanks guys. We do have pretty tight emission laws in the UK, get's checked yearly and you have to pass to be road legal.

I will get hold of the old cat, gut it and put it back on, see how it does.

I'm wondering if it doesn't help then the lack of power, shuddering and shaking and not holding idle will be something else, right? I should be able to get it back down to the garage to get the fuel pressure and vacuum testing done.

Besides that it's a compression test I guess...

Thanks!

Jedi54

iTrader: (7)

I think there's a compression test in your future regardless.
It would be good to know the health of your motor before spending more money trying to fix the car.

are there any rotary shops near you?

UnknownJinX

Cats are expensive, so make sure it's dead before you broomstick it.

But yeah, I'd double check the ignition components like mentioned. OEM coils are known to go bad after a while.

Navskhangura

No rotary shops near me unfortunately, there is a Mazda specialist but will speak to them on Monday to find out their experience with RX8's.

Tripled checked all the coils,leads and plugs today. Took the plugs out and could see the 1T plug (nearest to the front of the car) was wet, other plugs were a little dirty. Took them all out and gave them a clean.

Tried the deflood procedure (disconnect air flow and fuse for fuel), incase there was an excess fuel. Put it all back together and whilst it started nicely first time it's still got hardly any power, struggling to hold idle and shaking and juddering like crazy. Open my driver door and I can hear the cat almost popping, it's pretty loud.

Will try taking the cat off tomorrow and seeing what it looks like, could have got ruined already. Garage is closed so will get the old cat next week.

Not sure what else to try besides checking fuel pressure and vacuum leak.. conoresscom test will take longer to get organised.

Thanks!

BigCajun

iTrader: (1)

You can get a cheap HEI spark tester so you can check them yourself without going to a shop.

UnknownJinX

Didn't sound like you checked the coils, though. Spark plugs are only part of the ignition system, and coils fail often.

Use a spark tester or timing light to figure out.

Navskhangura

Good point, whilst I checked the plugs more closely, I didn't take the coils off and check them. I just checked they were wired properly to the right plugs.

Will take them off tomorrow and check again.

UnknownJinX

You don't have to take them off the check them.

Pull the wire off a spark plug and connect the wire to the timing light/spark tester, and see if the spark is strong.

Williard

iTrader: (18)

You need an HEI tester.

Thats it, easy and cheap.


Travis