mattris2k

Hello,

I have a 2005 S2000 with approx 87k miles on it. My CEL came on recently and I took it to a local AutoZone to have them do a scan for me. They came up with a P300 random misfire code, along with P301-304 misfires so all 4 cyl's misfiring.

I started off with the most obvious (and cheapest) stuff first - I replaced the air filter as the other one was pretty dirty, and I replaced the existing spark plugs with the same OEM ones that came with the car(NGK PFR7G 11S). The owners manual says the plugs are fine up to 100k but the plugs looked pretty worn so I figured I'd try that. The CEL went off for a day and then came back on again.

The CEL only seems to come on in the morning when I first start the car while it's cold. I find it highly unlikely that all 4 coils are bad and causing the random misfire. The car seems to run perfect after it starts to get up to temp but when it's cold it idles weird.

I also noticed a little bit of oil on the the spark plug boot that is on the coil in cylinder #3, so I'm guessing that is a valve cover gasket needing to be replaced. I doubt the worn gasket would cause a misfire (I could understand if there was some oil on the plug itself which could cause a misfire but there's not).

I know someone who works for a Honda dealership so I can get parts at a good discount so I have that working in my favor haha. Any suggestions would be much appreciated - this is really starting to annoy me. Lol.

Matt
-Rhode Island

AlexS2200

Compression test and leak down your motor. What you are checking for is bad compression due to piston rings or cyl head. Check if the motor is okay first and work your way backwards before you blatantly buy parts.

There is good information in this thread:
https://www.s2ki.com/s2000/topic/889...out-retainers/

The Ap1 to Ap2 retainers don't really apply to you in the thread but there is a lot of info about bent valves/cyl head leakage. IMO it is very common on S2ks to have bad cyl heads. I diagnose one every week on an s2k.

franky

Well, since you know someone at a honda dealership that can get you a discount price, why not get just one coil and see if that fix one of the cylinder. If it does then you can swap out the coil for the other cylinders and see if it fix the other cylinders too. If it doesn't then you either have bad piston rings or bent valves.

mattris2k

Thank you for the help. Out of curiosity, if I had loss of compression wouldn't I be able to notice power loss? I don't feel any power loss at all in the car whatsoever. Unless the compression leak is so minute that I'd barely notice any loss in power? Also, no smoke has ever come out of the exhaust since the day I bought it off the showroom floor. If piston rings were bad would I see smoke coming from exhaust, or some oil residue in the tailpipes? I will definitely take your suggestion and do the compression test and leak down but just wondering.

Thx again.

mattris2k

Thank you for the suggestion. Would I be able to feel some loss of power in the car if I had bent valves? The motor sounds fine, no ticking or knocking or anything. Car picks up and accelerates just as well now as when I first got the car. I'll do a compression test/leak down first and see how that looks. If that checks out then I'll go buy a coil. It just seems odd to me that one bad coil would cause misfires on all 4 cylinders and the chances of all 4 coils being bad are probably very slim I would think. If only one coil were bad, you'd figure there would only be a misfire on that particular cylinder. I'm by no means a mechanic but am just trying to think about it logically - then again, cars do a lot of weird things so maybe I should throw logic out the window lol.

What are your thoughts about this?

Thanks again.

LSUWALT

had same symptons, just had it fixed - valve adjustment and replaced front O2 sensor.....cured it.....then I replaced the 4 coil packs and it ran even better but I have much higher mileage than you - 154,000 miles

franky

You dont really notice a different because the valves are just slightly mininal bent to where its not sealing perfectly once awhile. Your motor will still sound fine. If it's badly bent to where it doesnt seal perfectly everytime, then yes you will definity notice. As for all coils being bad, its pretty slim but then again you dont know until you test them.

AlexS2200

The ECU knock sensor is picking it up misfire so it doesn't matter if you are feeling power loss because if you don't fix it you won't be able to pass smog because of a check engine light. Unless ur state doesn't care about smog like here in Cali.

HastedS2K

What kind of coil pack did you put on? oem ones? i bought BECK/ARNLEY Part # 1788427 ordered from RockAutoParts $192.31 set shipped. Does anyone used this?

Lalasissyboy

I had a very similar situation a few weeks ago. misfires on all cylinder and random misfire and oil on a single coil pack and no smoke coming out the exhaust. My car overheated at the track but still ran fine for a week until the problem started. Adjusted the valves and replaced the plugs. Problem was fixed for one day. Turns out my headgasket was blown and the block and head were both warped and the valves weren't holdin pressure once they took it off and checked them. Block warpage was still within spec. My car is currently at inline pro getting the head resurfaced and an aftermarket valvetrain for a pretty penny. I'm pretty sure this is close to a worse case scenario tho