Misfire Cylinder 5 - Advice?

[Michael Gain]

You said three of the four spark plugs had the oil/fuel on them. Was number 7 the one without residue? If so, it sounds like fuel, only in so much as that cylinder would be the most lean on the bank.

To your other question, the other injectors could create a cascade effect towards a misfire in #5. They all "report" to the same O2 sensors on that bank.

I would be interested in your fuel trims. I bet they are lean on that bank. The injectors dump more fuel to compensate. Number 5 injector is new so it sprays more fuel by injector pulse-- causing the plug to become fuel fouled.

That said, it can be something else causing a lean condition; other than the injectors... Vacuum leak, MAF sensor, O2 sensor, etc

 

[ihawkr]

You said three of the four spark plugs had the oil/fuel on them. Was number 7 the one without residue? If so, it sounds like fuel, only in so much as that cylinder would be the most lean on the bank.

To your other question, the other injectors could create a cascade effect towards a misfire in #5. They all "report" to the same O2 sensors on that bank.

I would be interested in your fuel trims. I bet they are lean on that bank. The injectors dump more fuel to compensate. Number 5 injector is new so it sprays more fuel by injector pulse-- causing the plug to become fuel fouled.

That said, it can be something else causing a lean condition; other than the injectors... Vacuum leak, MAF sensor, O2 sensor, etc

You nailed it, cyl #7 plug was the dry one.

EDIT: Fuel trims at IDLE, 1,500RPM & 2,500RPM (W/ Plenum reattached)

 

[ryanjl]

You all are above my paygrade here, but something I would note is that most people say pulling the injectors is a colossal pita. No one has ever said they come out easy. You are the first.

Which makes me wonder if someone wasn't just in there doing the same thing? I dunno.

 

[ihawkr]

After reading my fuel trims I am realizing that I probably left the vacuum line under the intake plenum undone. Going to reconnect and get new fuel trim data.... Stay posted.

EDIT: Fuel trims w/ plenum reattached posted above

 

[ihawkr]

You all are above my paygrade here, but something I would note is that most people say pulling the injectors is a colossal pita. No one has ever said they come out easy. You are the first.

Which makes me wonder if someone wasn't just in there doing the same thing? I dunno.

Very possible! I have quite a bit of experience under the hood as a Porsche Racing mechanic, but this one is throwing me for a loop.

 

[ktm525]

If they were original injectors it usually takes some serious slide hammer hits to get them out. Is this rig new to you?

 

[ryanjl]

If they were original injectors it usually takes some serious slide hammer hits to get them out. Is this rig new to you?

Yeah, first post said he just picked it up with 145k on it.

 

[ihawkr]

^^Yes, new rig to me. Looking at the condition of the #5 injector that came out with the rail, it had a good amount of carbon build up. Hard to say if it was original or not but I would agree with @ryanjl that it seems awfully coincidental that both the coil pack, as well as the injector from that cylinder show some evidence of being removed in the not-so-distant past. Seems like someone may have been in here in there already and either patched the fix or failed at an attempt to solve the misfire. We’ll know more with a leak down test but my instinct is saying an issue in the valve train is the likely culprit

 

[ihawkr]

New injectors coming in today, I'm going to replace all injectors on Bank 1 and see where that leads me...
Probably should've done the leak down test first but the leak down tester I ordered came broken and I'm in a pretty rural area so the replacement guage will be a few days out.

 

[ihawkr]

Quick update:
Replaced all injectors, coil packs, and spark plugs on bank 1.

Still misfiring on cylinder 5 only.

Don’t really mind throwing parts at it as its due for a lot of this stuff anyways, I figure it’s preventative maintenance going forward. But damn I’d like to be able to drive it at some point! Haha

I guess that pretty much narrows it down to rings or valves though which means it’s all gotta come back apart!

If anyone can think of any last minute Hail Marys to try let me know, otherwise, it’s wait for the new leak down tester and probably pull the head after that! Woohoo