CEL Misfire problem, worth to do a fuel injector cleaning service?
 

Recently I am trying to figure out the CEL problems with my 02 AP1. P0300, P0301, P0302, P0303, P0304, P1399 showing ramdomly after each time I reset the ECU. I notice P0301 shows up more frequently than the others so I thought it could be the cylinder 1 issue.

I have just owned this car for a short period of time so I know very little history about it. Car drives no problem but it feels a little rough when it's idle. I've search quite a bit on the s2ki forums and have done the following:

1. Cylinders pressure test - the previous owner told me he had done the testing and the results were satisfied.
2. Valve adjustment - the previous owner did it last year
3. Replaced brand new iridium spark plugs with gapping to 0.040, did not resolve the problem
4. swap ignition coils did not resolve the problem. I notice these coils are Denso 099700-070, I think they're not OEMs and looked pretty old. So I've ordered a new set of DENSO Part # 6732301 and they're on the way
5. Cleaned the MAP and zip-tie, no difference
6. Cleaned the IACV, no difference
7. Used a bottle of Redline SI-1 fuel cleaner few days ago, and I have not run out of the tank of gas yet. But same problem exists.

What else I can do? I think the Redline SI-1 is good stuff and normally they'll clean the fuel systems like new. Just wondering during the procedure will there any cabon deposits ripped off and cause the misfire as well?

The thing I don't understand is when I swap the spark plugs and coil among different ports, it always show P0301 first. Does it mean the coils and plugs are all good?

So the next step I plan to do is to check / swap the fuel injectors to see if the CEL pattern changes. I see in GTA there're some shops doing fuel injectors cleaning service. Would it be worth to do so, or just buy a set of new injectors? Pretty expensive for OEMs...

If fuel injectors are all good then what's the next diagnostics, retainer valves replacement? Any recommended shops?

Thanks,
Adam

Mileage, any known history of over rev/ bad shifting?
Sounds like leak down was ok. Double check valve adj.I have a friend throwing all these similar codes and popping at idle as well. Would be nice to know fuel pressure and stft/ltft, have yet to investigate

Btw if I recall you can open up the gap to 0.039 -.044 on oem plugs. What you wrote hopefully is a typo

Thanks for the suggestion... The engine was swapped few years ago with less than 50,000 kms on it. Previous owner said he had not ever gone track / raced with this car so I guess it might not have a bent valve? But definitely worth to check.

Idle is around 900 PRM stable. It does not pop but sometimes smells

I wrote a typo... The plugs I gapped them to 0.040

Always check compression/leakdown yourself and don't take what someone else does as gospel.

You should be doing compression and leakdown every couple years or after 30,000km let's say, it's a indication on whats going on with your motor (using the same gauges would be ideal, so you can see differences).

Check the valve lash and see if they need adjustment.

Redline stuff is good! just be careful on how much you use and do the calculations, caution on the less side, too much is not a good thing either.

Let us know the compression/leakdown and valve lash numbers

10 says you have pitted exhaust valves and seats.

Maybe I put too much Redline SI-1... I poured the whole bottle 15 Oz with full fuel tank, since the shop that sells it advised me to do so...

Will drive as much as I can and top up the gas more often to see if that makes any difference..

Will the fuel cleaner help on this?

Nope