mx5cartalk.com

I'm determined to get there...
UPDATE: Leads and plugs replaced and it did somewhat help my car along....however there is still something not quite right, and i can't work out now if it might even be ME! Rather than an actual problem with my lovely 5.

I admittedly haven't dríven too many Mx-5s and can't really compare it to anything so unsure whether it's just part of the character of the car..

I'm going to try and really best describe it here to see if anyone can shed some light:

Car is worse when cold.

I start engine, at 3-4k rpm I change gears into second, then as the rpms climb in second gear it seems to skip slightly, they continue to climb and there seems to be an irregular delivery of power, if you hold the gas pedal and slowly let those rpms increase, it seems to arrive in waves, only very slightly but it makes second feel sluggish, then moving into third its almost the same story though not as bad - then into gears 45&6 it's great - easily accelarates at high speeds, but those low revs and especially when engine is cold gives me the sh*ts!

It's always those low gears, always worse when cold. I'm wondering if it's the clutch? Fuel Filter? Any sensors?

Has anyone else had this problem? The car is great and does go pretty quick and i love those high gears, but accelerating from 2-4k rpms in second gear feels weird - is it me? Is the car fine? Is it just a cold engine symptom?

Thanks in advance, really need to get to the bottom of this..I know the 5 has a revvy engine but it feels like I HAVE to rev it in second..?

Does it idle rough when hot? Sounds like a timing problem or a clogged fuel filter.
Has the timing belt been replaced in recent times?

Worst scenario is that the belt could have jumped a cog which could possibly give these symptoms if you have checked everything else.

VVT system playing up?

o2 sensor dead.

To check just unplug it and see if it drives smooth again.

Dann

Upon thinking about this a bit more it certainly could be the fuel filter as the symptoms you describe are similar to my experience some years ago and I replaced the filter and it was fine. If it is faulty it will certainly affect the car under power and through the rev ranges you describe and then even out as you back off a bit.

Worthwhile replacing it anyway if it hasn't been done for a while...

Thanks folks! I can tell you the belt has never been changed but it only has 67k on the clock - however it's now hit 10 years old. I have also NOT yet replaced the fuel filter so I will also try this...

How do I unplug the sensor? Pictures would be BIG help.

So fuel filter, try unplugging sensor and timing belt...

anything else?

Mine doesnt have o2 sensor so no pics from me.

At the back of the cam cover there is a plug with a SINGLE wire leading down to the exhaust manifold, unplug that.

It WILL trigger an engine light until its plugged back in.

Dann

NitroDann wrote:Mine doesnt have o2 sensor so no pics from me.

At the back of the cam cover there is a plug with a SINGLE wire leading down to the exhaust manifold, unplug that.

It WILL trigger an engine light until its plugged back in.

Dann

It would probably be easier (and less likely to be confused with another plug) to follow the exhaust pipes from the engine down, about where the 4 separate pipes join in to one should be a thing sticking out with a wire going to it, that's the oxygen sensor.

I had this exact same problem about a month ago, I changed the fuel filter and that sorted it out.

not entirely sure what mx5 OP has but considering he has a 6th gear would indicate its a nb so i'm fairly sure it has stepped away from the primitive 1 wire o2, would more likely be a 4 wire o2 sensor. And hks kansie is right, just follow the your exhaust tract all the way to the exhaust port and you should be able to find it.

I agree with Dann - my NA ran like crap when I drove it more after purchase - I replaced the O2 sensor (NA sensor is a standard Repco part) and turned it into normal car..

Az wrote:anything else?

Another consideration might be coolant temp sensor for ECU at the rear of the head. They were a common problem on the NA6 causing cold idle/ running issues, but much less so on the NA8 & NB8.