When the CEL came back on, did you check the code again? And did you check your exhaust to see if it was actually misfiring? (like its sputtering or coughing from the exhaust)

Also, another one of my friend had a P1399 + p0302 and it was from a faulty/clogged fuel injector.

Check the fuel injectors. Could be clogged or faulty. And if it is, you don't have to buy new ones as you can send them in for ultrasonic cleaning. (Also go cheap first, try the fuel injector cleaners that you put into your gas tank. Ex: BG44k, Chevron Techron, Gumout Regane, STP, etc. Not sure if its the same brand names where you are since I'm from Canada, Ontario.)

 

Yes the codes were P1399 again along with other Misfire codes for each cylinder. One thing I notice is when the car is idling, sometimes the rpms will go low and surge. Sometimes when I reverse, the rpms drop as if the car is about to stall. The only thing left besides a valve adjustment would be the injectors correct? Wouldn't using the injector cleaner in the tank just clog them even more?

 

UPDATE: So I put in some Chevron Techron injector cleaner in the tank, didn't really notice a difference at all. CEL is still on, don't want to spend $600 on new injectors if I don't even know that's the true cause. What should I do next? I'm still driving the car here and there

 

 

So you have new coils + new plugs (properly torqued to 24ft-lbs)?

Did you do a valve adjustment yet?

Is there an ultrasonic injector cleaning shop near you? I haven't had luck with it, but it runs <$75 to clean/test and spray pattern report all 4 injectors if you really think that's the issue.

 

yup new plugs torqued to spec, 4 new AP2 coils. I put a bottle of chevron Techron injector cleaner and some days later the CEL started flashing whenever I'm idling for a while.

 

UPDATE:
Things I've done so far
1.Spark Plugs
oem NGK's

2.Coil Packs
2005 oem Denso coils

3.Injector Cleaner
full bottle of Chevron Techron

Taking my car to InlinePro tomorrow morning for a Valve Adjustment ($190) hopefully that's the cause for this pesky CEL

 

So I had a valve adjustment and compression test done yesterday, all cylinders were at 200 except cylinder #1 at 120. Shop is saying next step would be to take off the head to remove and inspect valves. Big disappointment guys

 

Bummer. Could you give us a little more info about your car? How long have you owned it? Mileage? Were valves tight before the adjustment? History of valve adjustments?

 

Its an 03 with 96k, I've only owned it for a little over a month bought from a dealer. 3 previous owners so I'm sure it was driven hard in its life. Unfortunately no service history on the car, so I've been replacing things. Best case senario the issue is in the head and not the bottom end. Around $1800 for the valve job. Can someone who's done/had the valve work done, can you guys chime in thanks