CEL light comes on
 

The cel light comes on when I rev over 5000 revs, GK Mazda in Sheffield have told me that it has an aftermarket cat on which is doing it's job fine but causes this light to come on. I lose no power or notice any problems when the light comes on but it is just annoying, they have told me to get this sorted I would have to pay £1600 for a new mazda cat etc but if I can live with the light on to just ignore it. I am going to live with it. It has just passed all emmissions tests so I will stick a bit of insulation tape on my dial screen to cover the light up. All I want to know os does this sound ok. The fault code is for a misfire. There is no power loss at all and everything is as it should be. Once I hit 5000 revs the light flashes for a bit and if I carry on at high revs it will stay on but if I drop the revs down and drive like a none RX8 driver (boring and slow) then it goes off. I am under the impression off Mazda that this is causing no harm and they have even told me to put some black insulation tape over the light instead of paying for a new cat etc. I am asking you guys the experts is this ok. Thanks to Huey for informing me that my last problem was the old starter motor - starts ace now

I thought misfires were caused by bad ignition? Meaning your coils/plugs/wires need to be replaced... If its a problem with the cat, wouldn't it be throwing a code for the cat/O2 sensors? :dunno:

^thats true, also is the light on constantly or does it blink?

Sorry my mistake, they have mentioned the 02 sensor, the coils,plugs and leads have all been replaced with new ones too. I am not at all clued up on cars so am trying to write everything that they told me lol. Once I rev hard it will blink and if i carry on driving hard it would stay on, but if i just resume driving normally it will go off. I would prefer it not to go on at all.

a blinking CEL indicates misfires, and you say everythings been replaces (coils/wires/&plugs) then that means you have a loose connection somewhere, or something isnt sitting right, also you should have the code read, according to your indications you have more than 1 code, i would assume that you have a misfire issue ( like i said before) and your gas cap (most common issue) is loose, thus the reason u have a constant CEL...have the codes read, and figure it out

I'm betting its going to be a code of P0300. I'm having the exact same problem. Not sure what to check my ignition and plugs only have about 4000K miles on them. Get the code for pulled for sure. Its not your cat, if it were you'd be bogging down in the higher RPMs.

Just been out in her and gave her a thorough thrashing, the light blinked a few times then just stayed on, I got no loss of power at all, didnt notice any changes at all. The light is going to have to stay on with a bit of black insulation tape over it.

In my opinion, giving up and just covering/ignoring the CEL is never a good idea unless you are 100% without-a-doubt sure why its there, which in your case it doesn't sound like you are. You really should at least check your coils and wires (easy 10 minute check) and make sure all the connections are solid if you're getting misfires...

Go and get that code read, I think its misfiring like mine is. I don't notice any performance issues at all when my CEL comes on either. That doesn't mean theres not a problem. I've had my code read, and cleared, and it reappears. That tells me theres a problem. You could be doing long term damage by ignoring it. I misfire is the quickest way to end your engine. Be careful.

sounds like you have at least 2 issues, ones for the misfires and the other is for something else