Stutters/misfires on strong accelerations

Car: AGN 1.8 20V Non-turbo Engine.

So I was trying to diagnose the problem for days now. No I don't have VAGCom to start with.

The problem started after going for my VAG Meet last Saturday. The car's pretty much in good shape at the moment and working as it should.

While at the VAG Meet (I don't know if this contributes the problem), I let the engine idle for like every 30 minutes (A/C were off) then turned the ignition off and let rest for 5 minutes through-out the meet. They were talking about exhaust sounds and such so yeah.. but I didn't rev hard or anything. Much easier to say: I didn't touched the pedals at all!

When we decided to leave, started my car again and getting ready for a 100km drive from the meet to my home. Started cruising along, with the A/C turned on throughout the journey.. then, just around 30km while on the journey and cruising at 140km/h, the engine suddenly stutters/misfires at my current pedal position! .. I let off the pedal, and the misfire is "kinda" gone.. Repeated the process, now not even 50% of the throttle, it misfires again!

I stopped by the road shoulder and visually inspect anything to do with the ignition. Turned off the engine. Opened up the engine bay, I noticed everything was tight (MAF Pigtail, Spark plug Cables, Coilpack, etc). Nothing unusual. Fired up the engine again.. heck, even during idle with some strong revs put in, the misfires are there!

So practically for the remaining journey, I had to only touch the pedal slightly to prevent the misfires.. all the way to my home! So then I thought, it must be the coils. Ordered a brand new coilpack, and fitted it like just now and the problem is still there??

This time, I went up to the fuse panel just for the heck to look for blown fuses. As I found, Fuse #43 seems to be blown! At first, I thought it was because of this that causes all the problem. Heck, replacing it seems futile too.

So what I did was:
- Replaced the coilpack
- Replaced Fuse #43 (Engine Control Elements)

I'm still using the never been changed spark-plug wires and Iridium Plugs (15,000km+ mileage on the plugs). I doubt its the spark-plug wires. And upon some searching, fuse #43 seems related to the Fuse Pump Relay? I'm having a thought of maybe the Lambda Sensor that might caused the problem too? But I'm not sure what does a faulty Lambda Sensor does!

Should I:
- Buy a new Lambda Sensor?
- Check the Fuel Pump Relay?

I don't know what else I'm missing here. I need her to drive on this 25th of June for my Lanparty and I just don't know what to do right now

(Sorry for the long post, just had to be detail about it)

I'm taking wild guesses too as of now, so yeah.

I might ask one of my mate's VAGCom later. Until I get it VAGCom-ed, who knows what might be the problem!

I replaced the coilpack already.

And guess what? I was being antsy and... I forgot that I haven't check the conditions of the spark plugs.






Should have checked it earlier!!

Now it runs smoothly, replaced all four and running with "NGK BKUR6ET-10" now. It was my spares! It was weird that the Iridium tips 'broke' early. Any ideas what caused this?

Oh well, problem solved guys!

*shrugs* Iridium knock-offs. Lesson learned I guess.

But the tip looked kinda fine for the last 5,000km (when I retighten all 4 plugs during my Oil change). Too hot?

Read some article on a site about reading spark plugs. It may might have caused by running lean or just too hot. The Iridium brands were fine actually.

Heck, until just now.. I was having vacuum leaks which I ... kinda didn't bothered where to find it in the first place.

Then, I don't know.. it just got into me where I should trace the whole vacuum line from the intake to the servo (is that the right name for the thing?), replaced the whole hose with some DIY, and.. well, idles better actually too now!

Man, I love DIYs!