Hi,

I've searched all the missfire threads, but did not find the exact problem I have. The car drives very well and pulls hard at WOT for the first 20-30 mile of driving. But then, if I try to go WOT, it starts to missfire badly. And the missfire seems to get worse the more I drive. Any suggestions?

My mods - 2.3, EvoGreen, 272 Cams, running around 1.7bar.

 

Change your spark plugs and gap them properly. Check the gap on the old plugs when you pull them to see if they expanded. Could be they're just fouled.

 

Ok, will check the plugs anyway just to be sure. It just seems strange though that it drives fine in the beginnig and I thought bad plugs would cause missfire all the time.

Also regarding gapping the plugs, I understood that iridiums (the ones I have) already come pregapped and you can not change the gaps - is it correct or am I wrong on that?

 

Back when I had a DSM and was posting to DSMtalk, somebody wrote in saying he was absolutely sure the plug for DSM's came pregapped. Another poster replied pointing out that the same plug was used in Honda lawnmowers. So much for the pregapped theory.

On an iridium plug the outer electrode is coated with platinum. This is very soft. The inner electrode is iridium (a metal with a very high melting point). Iridium is very brittle and can be easily broken. They need to be gapped but gapped with delicate care.

http://www.youtube.com/watch?v=lk70oyUEftY

 

So, are you trying to tell me that a single cylinder, air cooled, naturally aspirated engine running 87 oct, doesn't run the same spark plug gap that a 4 cylinder, water cooled, forced induction, engine running E85?! i kid i kid...


OP Fix the gap like everyone said...

 

Another possibility that comes to mind is a bad coil. Once some heat gets into it, it fails.