Ok,

I just bought a 00 ap1 (got screwed by the seller). After driving away w/ the car, i noticed the idle was very rough but there was no CEL on the gauge cluster. When i got home, i hooked up my obdii reader and got two pending codes. One was for the secondary air injection system malfunction and the other was P1399 for random misfire. Later on, the CEL turned on and i got a cylinder #4 misfire code.

Anyways, i've since swapped coils and map sensor from my friend's car and there were no improvements. We also did a compression test. The compression test numbers were 250, 245, 245, and 240 in cylinder #4. Note cylinder #4 was the one that misfired enough to turn the CEL on. 240psi still seems good, right? I also tried adding some oil to the cylinder to see if the comnpression increases. The first time i tried it, i put a few mililiters of oil in and got a reading of 240psi. I tried adding more oil and the gauge went funky on me. It would go up to 150-170psi then drop, go back up a little etc. I stopped troubleshooting at that point because I had a feeling oil got into the compression tester hose. I'm hoping I didn't lose complete compression in that cylinder.

Anyways, I'd like to know what you people think of the compression numbers I got. Do they seem ok? Ideally, I'd like to get a leakdown test to check for valve leakage but I'll have to wait until Monday for that. Any suggestions on what else could be wrong? I don't have a fuel pressure gauge and I haven't checked the fuel injectors yet. Note the spark plugs are 1 yr old Bosch ones (has some weird 4-tip design) installed by a Honda dealer 1 yr ago. They aren't the oem ones but the Bosch website claims they're ok for the S2000. All of them also looked consistent w/ a tiny bit of white on them.

 

You're at about 8% difference between the high and the low reading. Anything under 10% is fine.

Man, don't put those POS Bosch platinum sparkys in there. Please.

Our cars, as all Hondas, are very very picky about their sparkys. So get new NGK Iridium plugs. Then redo all the scans and stuff.

 

Compression seems fine sounds like plugs.

 

I almost guarentee its your plugs. I developed severe misfire with those gay +4s in my other car. never trusted Bosch plugs ever again after them. Get a set of NGK coppers 2 bucks each - just to make sure my guess is true.

IF the misfire stops, I was right, get a set of Plats or Irridiums from NGK - best spark plugs imho.

I'd rather run the walmart brand autolites than those +2/+4 plugs. VERY gimmicky and VERY badly made.

Just my 2cents.

 

i've heard the horror stories about the bosch +4 plugs so i'm ordering oem ngk replacements...they'll be here tomorrow

let's hope that'll fix my misfiring problem...

 

Good luck man, be sure to keep us updated!

 

If you remember to change the plugs every 10k miles, the cheap ngk coppers are the best thing you can get

Dont blow your money on any +4 or splitfire nonsense

 

just swapped the spark plugs...

after going back to oem ngk spark plugs, the engine stopped shaking violently but i'm still getting a random misfire (p1399) code.

i took an ohm meter to the old POS bosch +4 plugs and noticed one of them was way off. 3 of the 4 plugs measured infinite resistance on the center electrode. the last spark plug measured 12kohm. i'm guessing the internal resistor took a dump? if this was the case, would my coil go bad too?


ohh...and oddly enough, the air pump P1410 code didn't come during the cold start. might have been a fluke because it wasn't very cold out though

 

that actually looks more like a valve adjustment might be needed. 235 isnt that low

 

another update...

just finished a cylinder leakdown test and cylinders #1-3 had around 1-2% leakage. cylinder #4 had 3.2% leakage. i guess since both compression and leakdown results are good, my engine must be mechanically fine?

anyone have any ideas what i should do next? i'm thinking of swapping out all the injectors.


btw, i took an ohm meter to my new OEM ngk spark plugs. the center electrodes all measured around 4.5kohm which is probably correct because they have internal resistors. now in comparison to my old +4 POS ones that were in the car, those measured infinite resistance. wtf?