MX5 '99 NB missfire

Bazzaj · Postby **Bazzaj** » Mon Feb 13, 2012 10:47 pm

My 1999 NB has a very annowing intermittent misfire which seems to be heat related ie. it only happens after being left to stand for a while after reaching operating temp.
When starting up it runs on 2 cyls. and checking indicates the problem is with one coil pack, for cyls. 2 and 3. I have been trying to identify this problem for some time and have decided to try a new coil pack. (the expensive option). Has anyone else had this fault and can anyone tell me where to buy coil packs at a reasonable price?
thanks if you are able to help.

Russellb · Postby **Russellb** » Tue Feb 14, 2012 7:47 am

Yep very common problem.
I have fitted about 10 coil packs in the last 6 years all of the car displayed the same symptoms as yours.
Ebay have coils but there not cheep
http://www.ebay.com.au/itm/MAZDA-MX5-1-98-8-00-IGNITION-COIL-/300285595584?pt=AU_Car_Parts_Accessories&hash=item45ea6a8fc0
or maybe a COP setup for the same price

Zcootz · Postby **Zcootz** » Tue Feb 14, 2012 9:12 am

Hopefully not all 10 to the same car ???

spikes · Postby **spikes** » Tue Feb 14, 2012 9:16 am

ƒü¢k the coils off, go COPs. I built myself a set for $120, you can get them pretty cheap. And run a dwell reducer, saboteur was looking into getting some PCBs made up for approx $25. So thats $145 and you have a way better ignition system that the old shitty coilpack

Russellb · Postby **Russellb** » Tue Feb 14, 2012 9:33 am

Zcootz wrote:Hopefully not all 10 to the same car ???

No all different cars

Bazzaj · Postby **Bazzaj** » Tue Feb 14, 2012 10:25 am

spikes wrote:Flower the coils off, go COPs. I built myself a set for $120, you can get them pretty cheap. And run a dwell reducer, saboteur was looking into getting some PCBs made up for approx $25. So thats $145 and you have a way better ignition system that the old shitty coilpack

Ok, what are COP's, I'm new to this solution? How do I obtain,build or purchase COP's? Also PCB's and is a dwell reducer necessary?
Cheers, BJ

hks_kansei · Postby **hks_kansei** » Tue Feb 14, 2012 10:53 am

It's a bit hard since people insist on using acronyms for everything nowadays.

COPs = Coil On Plugs
Basically replacing the ignition system with one where there is a Coil pack for each plug (located directly on top of each plug)
I don't really know of anywhere that sells them, but generally people make them using the Coil on Plug system from a Toyota (I don't know the model) It requires a fair bit of custom wiring.

PCB = Printed Circuit Board, the green board with the gold wiggly bits all over it that you can solder all the electrical bits and bobs to.

Dwell reducers reduce the dwell from the Mazda ignition system to match the dwell required by the Toyota coils.
There are other people much more knowledgable than me in regard to this.

spikes · Postby **spikes** » Tue Feb 14, 2012 11:08 am

Bazzaj wrote:
spikes wrote:Flower the coils off, go COPs. I built myself a set for $120, you can get them pretty cheap. And run a dwell reducer, saboteur was looking into getting some PCBs made up for approx $25. So thats $145 and you have a way better ignition system that the old shitty coilpack

Ok, what are COP's, I'm new to this solution? How do I obtain,build or purchase COP's? Also PCB's and is a dwell reducer necessary?
Cheers, BJ

Coil On Plugs. Here's a kit

Here's the Saboteur's thread about the dwell reducer circuits.

Its really easy to assemble if you have basic knowledge of soldering and electronics. The wiring loom took me about 20 minutes to lay out and cut down the right size, and about another half hour to solder the pins and fit them into the COPs' connectors. The other end goes to the ignitor (1.6 applications). In your case of the 1.8, you'd wire it straight from your 1.8 coilpack plug since the 1.8 coilpacks have inbuilt ignitors.

The dwell reducer circuit is the reduce the dwell time otherwise the COPs overheat.

Stock dwell times from memory the 1.8's were 3.6ms and the 1.6's, 5ms. optimum dwell times for Toyota COPs is 2.1ms (correct me if I'm wrong) Without the dwell reducer circuit, the longer dwell times overheats the COPs causing intermittent misfires and eventually failure.

Dwell times = charge times for the coils before it sparks
To little dwell time = weak spark. Too much dwell time = overheated coil

At the end of the day, building a COP setup yourself will probably cost you $200 at most for all the wiring, dwell reducer circuit and mounting bolts and you end up with a far more superior ignition system that a coilpack and leads.