Hey y’all, bought a 2006 Xterra off of Copart (showed 120k actual miles) to try fix up, upgrade, and give to my sister since she likes them. Problem is, as it turns out, it runs extremely rough, obviously misfiring like hell and when it got delivered to me I was barely able to pull it into the driveway. Scanned for codes with OBD2 scanner and got P0300 (random misfires). So after thinking for a bit I just decided to replace the coils and spark plugs. Got the aftermarket coils from Amazon, but resistance is reading close to spec. After removing the plenum, noticed intake ports on cyl 1,3,5 are dark and wet with gasoline, spark plugs are all good, but cyl 1,3,5 plugs are black. Replacing all those things didn’t help. I checked for vacuum leaks, but couldn’t find any. I’m a mechanic, but I mostly work on semi trucks. I’m suspecting the timing chain and ready to tackle it, but I first must exclude any other possible causes as it’s a bit of a complex and time consuming task. This was 1 evening worth of diagnosing, so I haven’t had enough time to check compression. What would cause all cylinders on the same side of the engine to run rich? Thanks!
P.S. I did the dry compression test, shows all cylinders 145-ish PSI, a couple read about 148PSI (maybe while testing the first few cylinders I didn't crank the engine enough, hence the difference). I checked all the injectors’ resistance and got 12.1-12.5 ohms on all of them. The injectors are firing nice and misty fuel, not flooding anything. One concerning thing I found though - I assumed that on the injector connectors (2 pins) one pin would be 0V (ground) and the second one - 12V. But, what would seem to be, the ground pin shows 2.5V on all 6 connectors, if I remember correctly. Is that normal? I really doubt, but I’m limited on how much time I can spend per evening on this car. Any ideas? Thanks!
P.S. I did the dry compression test, shows all cylinders 145-ish PSI, a couple read about 148PSI (maybe while testing the first few cylinders I didn't crank the engine enough, hence the difference). I checked all the injectors’ resistance and got 12.1-12.5 ohms on all of them. The injectors are firing nice and misty fuel, not flooding anything. One concerning thing I found though - I assumed that on the injector connectors (2 pins) one pin would be 0V (ground) and the second one - 12V. But, what would seem to be, the ground pin shows 2.5V on all 6 connectors, if I remember correctly. Is that normal? I really doubt, but I’m limited on how much time I can spend per evening on this car. Any ideas? Thanks!