Engine surge at 2500 RPM

[tescoking]

does it happen when you start the car from stone cold?

[project.r.racing]

leads or coilpacks.

[NMX516]

Tired, faulty oxygen sensors can give that sort of problem around those rpm.... Does it clear up at higher revs?

[hks_kansei]

First up, replace the spark plugs.

That will help the ignition, and at the same time give you a chance to look at the old plugs and gauge what's happening (really roughly, black sooty = rich, white crusty = lean.. you can google what plugs should look like. MX5s run slightly rich nomrally, so it's not abnormal to see black sooty)

Plugs should cost a total of $15-$20
If that doesn't fix it, well they were probably due anyway.



Is it load dependant? ie: can it rev in neutral ok? just while driving?
When my old plug leads started to die it would run fine without load, and misfire under load (it would then foul the plugs and make it misfire at all times)




There really needs to be a bit more detail.
Does it start ok? or need a fair few cranks?
Does it idle smoothly? or vibrate a lot? (possibly running on 3 cylinders)
Blowing smoke?
Is the timing set properly? (not overly advanced causing severe pinging?)

[Black_Penguin]

Sounds like ignition leads to me.

Sent from my HTC One XL using Tapatalk

[Magpie]

Whilst not surging, I had a NA6 that would hesitate/bog down at around 2,000 RPM and replacing the leads ($70 from Plus) fixed the issue.

[aka_juffa]

ignition leads?

AKA Spark Plug Leads



Should cost you around $50 for a set of 4 leads from Mazda.

J.

[project.r.racing]

Second time in this thread they have been suggested. Pretty common symptoms for ignition issues.