My 2000 1.8 has started having a problem with hitting an invisible rev limiter! It is a standard 1.8, W Reg with 75K miles on it and generally has mild use by my wife since we got it 5 years ago. It is running on E5 fuel.
Recently I noticed that if you tried to rev it hard it bangs and pops at 4K when hot and will not rev past that limit. So I tried it from cold and it will rev to 6K before the problem starts, but the warmer it gets the lower the rev limit. I’ve tried it in 1st to 4th gear and it is exactly the same in all gears when hot.
Below the 4K point it runs perfectly.
I did a plug chop and they seem fine but as a precaution I replaced the plugs and leads as it was the cheapest first option.
Clearly it seems that it will be ignition or fuel based but I wondered if anyone had any thoughts about what to look for next - I am only an average home mechanic so if diagnostic tools are required I will have to find someone to do that. But any thoughts about what I can look for myself would be appreciated.
Hmmm
This is a tricky one but here goes.
Do you have a engine management lit BEFORE you start the engine?
Do you have an engine management light (EML) AFTER you start the engine?
This could be a catalyst / Lambda sensor issue, the car will run “open loop” whilst warming up then switch to “closed loop” when up to normal operating temperature.
This is a serious issue and the ECU should put out a code, if so the EML should be lit. Unfortunately the 2000 year NB mx-5 could have the old diagnostic port in the engine bay or have an OBD socket under the steering wheel.
Either way this needs to be investigated as you could cause serious engine damage if not rectified soon.
If you google MX-5 NB Diagnostic port you will see where too look, see Mazda MX5 OBD Diagnostic Plug Connector Location RHD - YouTube
Feel to come back with further information.
It’s a little unrelated but I think it’s worth adding.
I brought a 2.2l Vauxhall Carlton years ago and on the drive home, it wouldn’t rev past 3 and a half thou revs!
I drove it for 1 mile like that then it blew the engine, big style!
it blew a hole in the side of the block! and did serious damage to the head as well!
Thanks for the response - much appreciated. I had a new cat fitted for the MOT a couple of years ago as my friendly local mechanic couldn’t get it through without a new one. I’m not sure if it has an EML warning light as such - it has a red warning light (picture of a car with spanner through it). This comes on very briefly when the starter is turning the engine over but goes out as soon as the engine catches. That has always been the same since we got it.
I think I am going to try a new coil pack as it is a relatively cheap option and see if that fixes it - plus they are on special offer for Black Friday! I’ll report back.
Thanks Roy, that was going to be my next option unless anyone came up with a definitive ‘this is your problem mate’ and MX5 parts have them on special at the moment so I’ll give that a try.
Thanks for keeping the thread up to date.
I am a bit confused with the following statement:
“I’m not sure if it has an EML warning light as such - it has a red warning light (picture of a car with spanner through it). This comes on very briefly when the starter is turning the engine over but goes out as soon as the engine catches.”
Firstly the EML warning light is amber and should be in the rev counter dial at the bottom and looks like an engine picture. It should light up when the key is turned to ignition and extinguish when the engine is started.
I think the red light you mention is the immobiliser and this is a red light with a picture of a car with a key.
Please let us know if you do have the EML light showing on ignition.
Apart from that the coil pack is a good shout.
Ok - that’s weird. I don’t seem to have an EML warning light, and never have. The picture shows the dash when the ignition is switched on but not running! The airbag light goes out after a couple of seconds. The red engine light I mentioned in the previous post is above the temperature gauge on the right and comes on for a second when the engine turns over. Coil pack ordered!
