mx5 misfire problem?? pls help?

[erecsean]

hey guys, im new to the mazda scene and i recently just purchased a 1993 mx-5 clubman. but recently it has a misfire problem. i've changed the spark plugs and i have tried 2 set of leads but no one of them are brand new though. the misfire only happens when the engine is idling or when im taking off in 1st gear. any thought? maybe the coilpack??

[hks_kansei]

Were the plugs brand new?
Were they the right ones for the car? NA6 spark plugs fit but are a different heat, so after a little they cause a misfire.


Next would be leads, see if you can try a set from a known running mx5.
Leads can be funny on these cars, my OEM ones lasted 100,000km happily, then a set of almost new (~1000km) Top Gun leads lasted only 50km before they died.
My current leads are a set of Magnecor ones that are unknown age and have basically spent most of their life covered in engine oil. They work best out of the 3 sets (despite being the oldest and most abused of the lot)

[erecsean]

My other mate owns a na6 roadster and i've tried his leads and it still does misfire. I forgot to mention that it happens more often if i turn the a/c on. The spark plugs are brand new. Just normal ngk ones.

[93_Clubman]

Doubt it's the coilpacks - the NA8 was more reliable in terms of these than the NA6 & NB8A - it's probably plug leads - try a new set of decent leads. But before you try new leads check the ECU PCB as they have been known to have component issues like capacitors &/ or diodes - see ECU posts of CONTI.

[droo]

I'm sorry but i have to counter you 93_Clubman, please dont discount the NA8 coil packs. Not so much their ability to generate spark but their ability to not resist moisture in my experience has caused misfire issues on mine. My NA8 would cause consistent grief if they were moisture affected or on really cold mornings.

If you have access to an air compressor with a blower fitting, undo the coil leads from the coil pack, blow out and dry the 4 socket holes on the coil pack top. Using the air nozzle at a decent pressure for about 10 seconds per socket - to really get the moisture out. (some air compressors can also push their own condensate moisture in, so the 10 seconds will be enough to overcome both.

Also blow out the each of the tubes the spark plugs tubes in the cylinder head.
The ignition setup not partial to moisture of any amount in its system.

It's not going to cost anything (if you've got access to one, maybe even a tyre filler upperer at a servo could do it?) and it's a quick thing to do.

I'm putting my 2c in as I had a recurring problem with mine - if moist/wet/damp etc, the car would hesitate on loading at low rpm, feeling like the engine was running on 3 cylinders, felt like a weird buzz sensation and the car was gutless/poorly driveable at 2500-3500rpm.
When the engine eventually warmed up after 10-15, it was fine.

Until its left to cool down again, then hesitate again. I thought- how is it doing this for a full week after the engine was washed.
The only way to drive it was to really feather the throttle and drive extremely lightly through the gears in those rev ranges. Coasting was fine, acceleration was not.

My fix ended up building the COPs setup that was a hot topic on the forum almost exactly 12 months ago. Haven't had a misfire issue since, and can happily wash my engine bay without the misfire risk.

[93_Clubman]

No need to apologise Droo - I 'doubt' the NA8 coilpacks have failed as a component, but don't rule it out.

Of course, if water has been introduced to, or otherwise entered, the upper engine bay, then all bets are off, as spark plugs, wells, leads, coilpacks etc could all be affected.

Take away message for OP is to rule out the cheap/ simple potential fixes before spending hundreds on new coilpacks, which may not be U/S.

[shuey]

..sorry to hijack the thread, but I'm thinking of getting some new ignition leads as the OEM ones in my NB8B look a little dated and to help with cold starts. Would the Magnecor KV85 8.5mm be an overkill (ride's only going to be lightly modded) or would the Magnecor Electrosports 8mm suffice?

[erecsean]

problem resolved. bought a used coilpack from a wrecked mx-5. thanks anyways guys.

[93_Clubman]

Would the Magnecor KV85 8.5mm be an overkill (ride's only going to be lightly modded) or would the Magnecor Electrosports 8mm suffice?

Have used the same set of Magnecor KV85 since 2000 on my NA6 then my NA8, so can't comment on the Electrosports. However, Manga_Blue recommends these guys in Mitcham (Vic) make you up a quality set cheaper rather than buying costly off the shelf: http://www.performanceignition.com.au

If you do go the Magnecor for convenience, then NB8B runs coil on plug (CoP) on two cylinders, so only has two normal leads & two leads which incorporate CoP.

problem resolved. bought a used coilpack from a wrecked mx-5.

Good to hear - between you & 'dmad_dood' sounds like NA8 coilpacks might be reaching their used by date!

[shuey]

I see, I'll PM Manga_Blue to see how much does the ignition leads from Performance Ignition cost. Just that I saw a UK seller over on eBay selling Magnecor KV85 at a good price. Might as well get some NGK plugs while I'm at it. Thanks!

[Mr Morlock]

If a car is running and starting ok why replace the ignition leads- what is a dated spark plug lead- cracked? Perf ignition is a local Melb source- easy to just go and talk to them.

[manga_blue]

I see, I'll PM Manga_Blue to see how much does the ignition leads from Performance Ignition cost. Just that I saw a UK seller over on eBay selling Magnecor KV85 at a good price. Might as well get some NGK plugs while I'm at it. Thanks!

That was about 5 years ago. Just drop in and see them. They'll test and replace if necessary.

[shuey]

Yea, guess ill get them to have a look/test
Just that it takes a bit of time to crank during cold starts and looking back at the previous owner's service receipts, the ignition leads hasn't been changed for a number of years.

[93_Clubman]

Just that it takes a bit of time to crank during cold starts...

Assuming you mean it takes more cranking than usual for an EFI motor, as opposed to the slow cranking of a low charge battery, check the green 'EGI' relay (not the EGI/ fuel injection fuse) in the main fuse/ relay box in the engine bay. The internals on some relays corrode & can cause starting issues - the relay can be removed with a bit of jiggling & the green plastic cover can be carefully prised off & internals cleaned if necessary. If plug leads haven't been replaced for many years, & they are Mazda OEM ones, then it's usually well worth replacing them.

[manga_blue]

You might also get an auto leccy to test the battery. It may be getting old and not taking a full charge any more