Ignition issues,help!

[Kakkyo]

Lately my car has had issues with starting up or the occasional misfires on very hot days. When Radioactive had ran some Seafoam through my car the issues seemed to go away, but with summer finally going into full swing, the problems are showing up more often.

One of the issues that's the most troublesome is that if the car has been warmed up for 5-7 minutes, driven a short distance, then shut off... On restarting the car about an hour later, the car goes into a limp, misfiring mode.

Last night was probably the worst occurrence of the issue... In the morning, everything was fine. Later around 6pm, the ignition would click but wouldn't turn over after being in the sun for hours. Around 10pm on returning to my car, the car would do the clicking again and wouldn't turn for a few minutes and on eventually turning... There was a squeal like a belt was slipping and then a hiss from the passenger side area of the engine.

The last codes that were read from the engine were a 0300 (random/multiple misfire) and a 0420 (catalyst bank 1 threshold failure). The only thing is from reading the pointy boards and their articles in the Garage section, it seems like it could be a mixed bag of anything...

I have seen things like faulty plugs and/or wires, failing coil pack, bad oxygen sensors, bad catalytic converter, the Miata EGR valve failure (from the service bulletin), complete replacement of the vacuum hoses for the EGR system, dismantling the intake manifold and throttle body to clean out carbon deposits.

I had installed new spark plugs and plug wires about 600 miles ago, so I don't think that they would be the issue. I am at my wits end and I would hate it if it was something else I didn't account for while being out even more cash.

Anyone have any insight about this? Any help is appreciated and thanks in advance for any help provided.

[sammm]

Could be the coil pack. If it has been mis-firing enough it could kill the too.

[Kakkyo]

Ugh... I'd hate to think that it could be the coils and then to factor in stuff like new oxygen sensors and cat soon afterward... In respect to that solution... any ideas for cheap pricing for parts?

[sammm]

You might check with Stevan (Rogue) at Miata Solutions, or Gary at Track Dog (trackdog) for used NB parts.