Update 11/7: replaced the ecu with a used one from ebay, car runs fine for over a week now, I did a 250 miles round trip last weekend without any issue. To double confirm it, I swapped the old ecu back on and it started to misfire right away, so I'm pretty sure it's the cause and it's solved now

Hello, I had a bad misfire a couple of months ago, one bank was totally gone, I replaced the ECU caps according to the suggestion by some forum members and the car ran good for a couple of days after that. A few days later, it started to misfire again on cylinder 6 and 8, so I replaced the spark plugs hoping it will go away, and it did for a while, although I always felt that it's not running right, e.g. vibration at idle and speed over 50(which could be a wheel issue, but I don't remember it happened before the incident).

Last night it happened again, the code pointed to cylinder 6, but I felt it's more than that, since it was as violent as the first time when the engine lost 4 cylinders. I was suspecting the distributor, I don't know it's condition. The car is a 96 and just past 200k. Please provide any other opinions/ideas on this issue, thanks!

 

Which spark plugs did you use?

 

NGK (3764) BKR6EIX-11 Iridium IX Spark Plug

 

Yea that's good stuff.....I'd do this, take the plug form 6 and put it in say 4...if the misfire follows it, it's the plug if it's not then it could be the coil pack or wiring or maybe even distributor.

 

The type of spark plug is basically irrelevant until the root of the issue is addressed.
After reading your initial post it sounds like you started by replacing caps in the ECU. Is this correct? Did you, by chance, eliminate other potential faulty parts first like cap/rotors and plug wires?

 

I did address that for op.

 

Are you also answering the question I asked the OP?

 

Like I said I addressed your question already to op. Scroll up.

 

Prefer to hear it directly from him.
Which troubleshooting steps were taken BEFORE choosing to replace the ECU caps...

 

3rd try: I already asked what you asked. So we will both find out.

But judging from the OP nothing other than what was stated. That said I'd like to know as well. I'm worried as I'ma be changing plugs soon as well

 

I haven't, from the symptom that misfiring only happens at bank 2, I suspect the cap/rotors might be the cause, already ordered the parts, won't hurt if I change them

 

The ECU cap replacement was my first step, it can cause misfire and I had intermittent faulty speedo, the technician that did the work found a few caps were definitely leaking fluid, and the car ran fine for a few days after putting the ECU back.

 

You mentioned in the first post one entire bank was gone. How did you determine that?
Cylinders 4 and 6 are in the same bank AND also both fed by the same distributor.
if you haven't already seen this it may help...

 

I had 5 codes at that time, cylinder 2 4 6 and 8 and also a random misfire code, the engine felt stalling especially when idling, it felt the same way this time, although I just had one code from cylinder 6.
From the diagram, cylinder 2 8 and 4 6 are fed by the different distributor? So it might not be the faulty distributor, since the chance of both went down is rather slim

 

Still possible, im leaning toward wire or maybe even faulty plug.