Where to start, well my car is throwing the p1399 OBD code, along with a cylinder 1 misfire and sometimes it will have another cylinder misfire as well. ive changed the spark plugs, the timing is good, the valve spacing is good. but i have no clue why is continues to misfire. any suggestions?

i will also note that the code for secondary air injection will randomly appear as well.

thank you

 

Coil packs, maybe?

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swapped around my coil packs, no change in the cylinder that misfires

 

Do a compression test. If that cyl is lower than the rest, look into doing a leak down to find the root of the isuse.

 

Remove the coil pack from cylinder 1 and see if you have any oil in the spark plug tube. Just a shot in the dark, but a leaking seal will cause a misfire once the oil pools up in the tube.

 

UPDATE: so I've been gone a little bit and I haven't been able to get around to the compression test but there's no oil in any cylinder and the codes I'm reading vary from cylinder 1/3 misfire accompanied with a p1399 or its p1399 accompanied by a p1410. Also, once I reach about 3500 rpm and the car begins to actually accelerate is when it misfires. I appreciate all the help.

 

P1399 is a generic code that generic testers will throw. I've never seen the HDS throw that code and there is no listing for it in Honda's database. That being said, disregard it. When you fix your misfire, the aftermarket code reader will no longer pick up that code.

The p1410 is your air pump and relay. It is a common problem on 00-05 S2000's. Replace your air pump and the relay for it or do the air pump delete mod found on this forum.

The misfire could be caused from many things. Compression is a good start as some have posted. I have also seen an alternator with a weak output cause random misfires in the S2000. It generally throws the code when at idle if this is the case. Also, you can look at the gauges cluster at idle and watch it slightly flicker for a good indication that the alternator is getting weak. A good multimeter test is a surefire way to tell too.