How's it going s2k fellow drivers...the situation. 2000 Ap1 s2000. Multiple misfires p1399 p301-304. Things that have been done.

Plugs have been replace twice
All new coil packs
Fuel injectors test 90%+
Compression test 215 all across
Valves adjust twice
MAF whack and ziptie

Really at a loss guys I know leakdown may be another suggestion but misfire is not continious it comes and goes from some days to.some car drives fine only when in misfire mode. No knocks nothing it purse except for when in misfire mode again

So at a loss for the moment can anyone give insights or suggestions on how to figure this situation out. Thanks ahead for any insights

 

Did you check fuel pressure

 

Haven't checked fuel pressure will put it on the to-do list

 

I've had 220 220 210 200 on my engine before. Fast forward 8 months; turned out to be a bent valve. Compression test got worse over time. And in my opinion, the psi value themselves are not really consistent between different gauges.

Ap1 90k mi.

 

A leak down test will tell you if it is a valve

 

Is the misfire at idle or under load? The freeze data will tell this. This will narrow it down considerably.

Do a leakdown as suggested, it is the proper way to find a cylinder short on sealing power.

The leakdown test was developed to show where the pressure leak is going, not just percentage.

The tech should be able to trace the audio signal of the leak in a perfectly silent shop.

If he can't, then don't bother. Percentages mean nothing without a repair path to follow. In almost every single thread I have seen on s2ki, there have always been percentages posted without a solution to fix the car.

If you do a LEAK down test, you find the LEAK plain and simple.

 

Just asking:


Is the ECU fast enough to detect individual misfires?
(I think it is as the ECU is fast enough to decide what to inject and when to ignite per cylinder - even at 9k...
... allthough it could be the ECU decides per 2 crank cycles what to inject for all 4 cylinders)

What I mean: if one gets P1399 combined with only P0303, can one be sure it IS something with cyl - valves - rings - #3?
A step further: if one gets P1399 and all the P030x (1-4) can one be sure it is something with the fuel intake, like fuel quality, pressure, MAP or head gasket?

To the OP: do you always use the same fuel?
How sure are you the fuel is the same quality?

 

My mystery misfire, which came and went over the course of 6 months ended up being a severely cracked valve spring retainer.

It was odd though. I initially replaced the ignition coils and it went away. Came back about a month later and I reset the ECU and it was good for another month. It eventually got to the point I was hearing valve train noise which sparked me to think about the retainers. A retainer on cyl 1 was hitting the rocker...

However, if you adjusted the valve lash and it didn't immediately go away (temporarily), then it is probably something else.

 

Have you been getting any other codes besides the misfires? O2/ catalyst related codes??

I fourth the leak down test, it's the only thing you haven't done and should of been one of the first things to check.

While your doing that, have a close look at your retainers.