2001 ap1 with 167k miles , new denso map , new denso coils , new denso plugs , new denso 02 , valve adjustment just done , and injectors just serviced .
Hi , the car is tracked but not beat on . I’ve been chasing this misfire code . The car does feel smoother with all these new parts but from idle to 3k I can feel a slight miss. It almost feels like sometimes it more there and sometimes less . It also does seem to be better when the car is fully warm . When I did the valve adjustment I looked at the retainers even though the car has never been over reved by me (looked fine ) . I just changed the oil and looked closely at the oil for any metallic particles but everything looked normal . The tct is original but I really don’t hear anything. What could I be missing ?

 

Are you 100% sure that your Denso parts are not counterfeits? There's been a lot of talk here recently about the coils and how easy it is to end up with fakes if you don't buy from reputable source.

 

Everything from Rockauto only .

 

Drove it some more today . The misfire comes and goes. The engine check light will come and go with the only code being 1399 . The misfire will only be at 3k or less. When the engine is fully warm it idles like butter . I’m starting to think it is fuel related. I am leaning towards fuel pump because I am not getting an individual cylinder misfire ? How does that sound to you guys ?

 

Do you have good compression across the cylinders?

Thanks!

 

i have not checked but does not burn oil at the track and on the straight pulls just as hard as the other group of s2000s I run with .

 

You might want to think about it. Just to rule out one weak cylinder causing this issue.

 

just my thought , if it was one weak cylinder I would get that cylinder code but I am only getting the p1399 multiple misfire code that comes and goes .

 

I like to rule out simple, cheap things first before diving down the rabbit hole.

But that's just me.

Good luck with your engine!

 

I recently had an issue with CEL after valve adjustment, (stupid shop made gaps twice the required), redoing those properly solved the problem.
Maybe also try double checking those? should not be as costly since you do it yourself