I have been running on 5 cylinders for a week now and I think my fuel injector (cylinder 5) is bad.

So far, I have replaced my ignition coil pack, spark plug cables, and spark plug, and I am definitely getting a spark.

I have disconnected the spark plug cable from cylinder 5 and started the car, and it idles exactly the same as if I had it connected.

I have also used my ghetto stethoscope (a screwdriver) to check that the solenoid is clicking in the fuel injector.

Its a bit of a bitch to remove the injector to swap it with another cylinder, so I haven't done that quite yet, though I think I'll do that this weekend.

The only things I can think of that are causing this would be either a bad/clogged fuel injector, or a stuck valve.

Is there anything else that could be causing this?

If I end up replacing the fuel injector (fairly cheap), would I need to buy just the one or all 6?

Thanks in advance

 

Sounds to me like your troubleshooting and diagnosis is right on the nuts. Refreshing to see that once in a while lol. I see no reason to replace all six injectors other than the fact that things on cars in multiples generally tend to go bad all at the same time.

 

If you disconnected the spark wire and there's no change in the way it's working, and you've replaced everything as stated, then either you're right that the injector isn't firing correctly, or the plug gap is way off (should be .032). I do hope you're not driving it with an active misfire - it throws the engine out of balance and could screw things up badly.

Try running seafoam in the gas - just let it idle so long as it's not actively misfiring. It may clean whatever crap is causing the issue. You could also pull the injector and have it cleaned by an engine shop. Be sure to reassemble it with new o-rings.

Final idea - download the Bentley manual from the sticky posts up top, find the wires that correlate to your bad cylinder, and ohm them out from coil pack to ECU. You could have a frayed/damaged wire causing that cylinder to have issues. Long shot but worth bearing in mind.

 

It doesn't misfire all the time, only when it is fully warmed up, when it starts to shake and hesitate.

This issue actually started to get serious when I put some Lucas fuel treatment in the tank, after ~20 miles on it.

I have added some fuel injector cleaner to the tank and refilled from 1/4 tank, and it seems to be running much better now, though it has hesitated a couple times on the 10 mile run I just took it on. I think I'm going to order a replacement injector (it's only $40 for a new one) and O rings and give that a shot just because it's so cheap.

I will definitely ohm out the cable, it is a little on the older side and its worth a shot since its right on top of the engine anyway.

 

Forgot to add OBDII codes:

P0305 (Cylinder 5 Misfire, it hasn't come back since resetting earlier today)
P1127 - Long Term Fuel Trim mult.,Bank1 System too Rich
P1129 - Long Term Fuel Trim mult.,Bank2 System too Rich
P1141 - Load Calculation Cross Check Range/Performance

 

I neglected to mention that I had replaced my air filter with a factory fresh K&N as well, and the oil off of it screwed with my MAF. After cleaning the MAF and IAT sensor for good measure, my hesitation is gone entirely, but the misfires still occur at cold start, and continue until the engine is warm.

I haven't done too much research into it yet, but does anyone know what might cause misfires on a cold start?

Thanks in advance