Hi I'm trying to get some info after trying to diagnose misfire issues when a recent CEL popped up. My initial code was P0301, cylinder 1. I have already swapped coil packs between cylinders 1 and 2. Shortly after I ended up with a P1399 (no CEL, I just plugged the scanner in). A day later after running the car about 15-20 min to further diagnose, CEL finally popped up with P0302 and P1399 clearing out, assuming that the misfire followed the coil pack. I ended up getting a little curious and decided to get a multimeter and run a test on all the coil packs to be fully sure ( and im also not sure the test method). Now I'm not so sure any more.

I've "tested" injector 1 by doing the screw driver trick and did hear a constant ticking.

After doing some searching through the threads one of the ways to test this was to test them 2 ways hot and cold with a multimeter. ( Engine warmed up at idle for about 15 min)
Source: https://www.s2ki.com/forums/s2000-un...-228429/page2/

During testing, I hit each pin with leads to the multimeter and below are results ( cold / hot):



For further context, I'm pretty novice at this and seemed pretty simple enough to do for now. As for the S and it's history: 2002 AP1 165k miles on the odometer, mostly stock except for the TCT which was replaced about 4 years ago. Valve adjustment was done and gaskets replaced roughly ~150k miles ~8 years ago. The car isn't tracked and is pretty much garaged now.

In terms of replacing the coil packs, can I also get some confirmation on the part numbers needed based from this thread, https://www.s2ki.com/forums/s2000-un...220381/page10/ ? I know year numbers and versions were thrown around but no definitive part numbers provided for the compatibility for the 04-05 as it seems there was some confusion, or I misunderstood while reading through it.

These are the next steps I'm planning to do:

1. Replace spark plugs
2. Find a mechanic or someone that can
   1. Test the injectors
   2. clean / swap injectors ( im not too sure how hard this will be for DIY)

And as a little side note, not to derail from the main issue here: I'm looking for recommendations to try and restore the car as best as I can for a DIY project. What are some good starting points (Looking to keep this NA,)?

 

so the misfire moved to cyl 2 after you swapped the coil packs? Sounds to me like you may have found your issue. You could swap 2 and 3 and see if that makes it move to 3 as another check.

I had more than one bad coilpack and no measurement with a multimeter could see any difference in those coils. Unless the primary side failed you wont find it with a meter. This is a coil, so the secondary is only coupled magnetically to the primary. So if you are testing at the connector pins an open or shorted secondary (common when the coil age and the internal insulation breaks down) likely is not going to find anything.

 

Thanks for the insight on the multimeter stuff. After swapping 1 and 3, noticed that idle seemed just as rough as initially and the misfires are audible from the exhaust side. No CEL since I'm disconnecting the battery every time the I take out the packs, but I'm getting P1399. So im moving forward with into replacing all the coil packs due to their age (each of them ended up having some slight discoloration), just waiting on them to come in.

 

Which coil packs did you order?

 

Part 30520-PCX-007. I prefer the consistency and removes the guess work I had to do earlier so I replaced all 4 coil packs.

Once I had them in, any audible misfire sounds seemed to have gone away and P1399 did not appear w/o CEL as noted before. Looks promising. Although, I did notice would could possibly be water vapor or fuel injector cleaner vapor coming out of the exhaust, I hadn't noticed this before. But overall ran smoother after a 10 min drive. Idle seemed to be lower than usual, but for now I'm not too worried about that.

 

Having a similar issue with my 01/ 39k miles.

replaced the plugs (OEM NGK Laser Platinum), did a valve adjustment. CEL and code went away (p301), however, still having a rough idle/ misfire sound/ vibration on cold start. Going to order new coils next, also trying to order a new Billman TCT, as I notice a small bit of oil near the existing TCT

 

Anything else after cold start? When it's fully warmed up, do the symptoms persist? Are you sure you're still misfiring after the CEL and code went away?

You can probably try cleaning the IAC - https://www.s2ki.com/forums/s2000-un...-valve-492738/ - for rough idles to start off with.

I'm not too sure if coil packs would be worth the change at that low mileage. Searching through the forums, I've read the coil packs last on average 90k-100k miles. I've had to also replace the VTEC solenoid gasket for an oil leak as that ended up being old, hard, and flattened out years ago.

 

The engine seems overall more noisy than when I got the car at 31,xxx miles. I would say the idle smooths out after about 10 minutes of running, and getting to temperature. There were no active codes when I checked yesterday, while the “rough idle” symptoms were active. I cleaned the IAC last year, but maybe I’ll give it another shot this afternoon. I’ll keep you posted

 

From what I've experienced throughout this thread is that a misfire code can be thrown even when all the codes are cleared on battery disconnect and even without a check engine light (P1399). When the CEL would show, it would be specific to the cylinder in which the misfire occurs. I suppose if you're no longer getting them, then it might be a red herring. If that's the case maybe open up a new thread and see how others can chime in. It's probably best to keep things on topic to avoid confusion for searches.