I picked up non running project D2, 2004 with 100k miles.
After I got it running, I put about 100 miles on it without issue, only throwing a 1171 & 1174 code, which I decided was dried out fuel injector o-rings.

I put in the new o-rings, NGK copper plugs, NGK wires, and a generic coil pack (one of the cheap ones on Rock Auto).
The 1171 & 1774 codes are gone, but now it is idling noticeably rougher. It has a stored P0305 cyl 5 misfire code with a pending p0300 random misfire code.
Under normal driving, it seems fine without issue but is noticeable when idling.

I put the original Bosch coil pack back in with no change.
I put in a set of remanufactured injectors with no change
I put in a Champion copper plug on cyl 5 with no change.
I put the new generic coil pack back in and put in a set of Kingsborne 7mm wires with no change.
I swapped out the MAF, Purge Valve, ICV with no change.
I put in another remanfucatured injector into cyl 5 with no change.
I replaced the intake manifold gasket (small one between the upper & lower).
There are no visual breaks in any wires.
I've sprayed carb cleaner around the intake with no effect.

When I first did the work, the lower intake bolts were a bit loose, so I tightened them by hand with a wrench.
One of the times I was in there, I replaced the valve cover gaskets and the head/rocker looked normal. It appeared to have a recent head job as everything was so clean, and the outside of the head was cleaner than everything else.

I checked the compression on cyl 5 and it holds at 170psi.

I'm not sure where to go next.
It was obviously something I did, as the misfire and rough idle weren't there before.

Has anyone run into a similar situation?
Thanks

 

I'm still fighting with this issue.
I swapped the #3 & #5 fuel injector with no change.
I swapped another coil & plug in, with no change. I pulled the plug and left in in the wire and cranked, and it is visually getting spark.
I did another compression test, and it held at 160psi (not 170, my mistake).
Out of desperation I swapped the fuel pump with a spare that I had, no change.

Normal driving is good with full power & no flat spots, misses, or noticeable misfire.
No other codes or noticeable problem.

I'm not sure where to look next.
Any suggestions? Anyone have a misfire at idle and figured it out?

 

Do you have a scan tool that you can monitor 02's and fuel trim? Also, are you a hundred percent sure about firing order, since you have apending random misfire code also?

Other then that, it sounds like you've done proper diagnostics. The only other thing l can think of would be...did the injectors have the plastic tip protectors in place, when removing? Sometimes these are cracked and missing, wondering if piece fell into manifold port or something. I've seen injector plug harnesses (that runs along fuel header) that were in terrible shape and needed wires repaired, also.

 

I’m having almost the exact same issue at the moment. However I had a catalytic converter code pop up once and a lean (p0171) code too. I have new ( 6 month old) plugs, wires, o rings, upstream o2 sensors, MAFS. My down stream o2 sensors seem to be working just fine on live data , and I don’t know what to look at now.

 

Having the exact same issue as your original post.

Chased away P0171 and P0174 code by replacing my fuel injectors.

Now getting a P0305 code. Did all the same checks as you and everything seems to be in order but the car is still missing and rough idle.

Your original post is so similar to my issue. Only thing left for me to try is new coil pack.

Were you ever able to get it sorted out?

 

second that on the injector harness. What looked good outside was really corroded cracked wiring on several of the injector leads about 1 inch from the injector plug.