Signs of detonation on #4 spark plug?

[Marwil]

Looking for input on my # 4 plug folks (NGK BPR7EIX). Does this look like detonation?
This the only plug that looks looks this out of the six. Wondering if I have a bad injector on number 4 cylinder causing the cylinder to run lean?
The reason I am digging in to this is that I have been chasing a persistent mid-range misfire. It can be readily perceived between 2000 to 3000 rpm, it may well occur at other ranges too. Adding some fuel or manipulating timing has little to no effect. Adding a lot of fuel seems to help but I mean richer than 13:1 afr.

[winders]

Have you tried a new injector in #4 or have you had your injectors R&R'd lately?

[Tea Tray]

A pic of the other plugs would be nice.
Like Winders said above, try swapping injectors to another cylinder.

[Flat Six]

1) Check for air/vacuum leak at #4 intake; prolly a good idea to re-tighten intake manifold bolts.
2) NGK's EIX-series plugs are platinum tip (obvious from pic, too); go copper instead. And unless there's a specific reason you're using a colder (7-series) plug, use BPR6ES or BPR6EY.
3) Check ignition wire(s) too, including connectors.

[manbridge 74]

Fairly new plug?

Looks oil splashed on insulator.

Leak tested engine lately?

[Paulporsche]

In addition to what the others said, you may want to replace all the other O rings for the injectors.

You should also do a volume test of your injector outputs. It will tell you right away if you have any clogged injectors, lines or fuel distributor issues. There are threads on this. Easy to do. Tony even has a test rig setup for this.

[Marwil]

Thank for the responses folks. @Tea Tray - I didn't include pics of the others as they seemed fine and did not show any of the discolouration on the tip like #4

@Winders - haven't switched out #4 injector with another nor removed or cleaned any. I do have another set of 24 lb Bosch EV6 type from Five-O Motorsport on the way. The current injectors are Accel - not sure of the quality.

@Flat Six - The BPR7EIX plugs are Iridium plugs and have been used by others here. If I go to a 6 heat range in the NGK I think that would be hotter. Would that increase the possibility of detonation?

Checked for intake leaks with a smoke test and found none. I have done a leak down on four of the six cylinders, so far the they are running 6-10% on a cold engine. Heading into the garage right after this post to do the last two. I'll post if I find something drastically out of whack.

@Paulporsche - I agree an injector test would be a good step to go to. I might go this step if the new injectors indicate problems - the new set are a flow matched set. Do you know of a good injector cleaning/service centre up here in Canuckland?

[Flat Six]

Originally Posted by Marwil

Thank for the responses folks. @Tea Tray - I didn't include pics of the others as they seemed fine and did not show any of the discolouration on the tip like #4

@Winders - haven't switched out #4 injector with another nor removed or cleaned any. I do have another set of 24 lb Bosch EV6 type from Five-O Motorsport on the way. The current injectors are Accel - not sure of the quality.

@Flat Six - The BPR7EIX plugs are Iridium plugs and have been used by others here. If I go to a 6 heat range in the NGK I think that would be hotter. Would that increase the possibility of detonation?

Checked for intake leaks with a smoke test and found none. I have done a leak down on four of the six cylinders, so far the they are running 6-10% on a cold engine. Heading into the garage right after this post to do the last two. I'll post if I find something drastically out of whack.

@Paulporsche - I agree an injector test would be a good step to go to. I might go this step if the new injectors indicate problems - the new set are a flow matched set. Do you know of a good injector cleaning/service centre up here in Canuckland?

A colder-range spark plug is more susceptible to fouling and misfire. Didn't read anything in the OP that lead me to believe your engine specs/setup require a colder-than-specified spark plug. YMMV.

BTW, not all iridium plugs are created equal. IMHO, NGK makes better iridium plugs than most other manufacturers though. Iridium and platinum plugs were designed for extended service life in modern engines with high-energy ignition systems where plug replacement intervals are in the 60k-100k+ mile range because it's so damned difficult to access some of the spark plug locations.

[Paulporsche]

Marwil,

I tried someone here in TO but they said the injectors and system were too old for them to work on.

Actually, there are some things you can do. I blasted some spare K Jet injectors I had recently by pushing a nozzle of a new can of Brak Klean into the inlet end and wrapped it with a cloth tightly so all the force was directed through the injector, producing a spray out the output end. This produced a good pattern showing no clogs.

I haven't tried this but I've read that you can also try shooting shop air at, say 60 PSI or so, through the injector and listening for the squealing sound they make.

The flow test was the one I was referring to in my original reply. You can pull all the injectors, leaving them connected to the fuel lines, and place them in bottles. You then turn the key to the on position and raise the sensor plate next to the fuel distributor for several seconds. This will cause the fuel to spray into the bottles. You can then check to see if number 4 (or any other) injector is underperforming or if that line is clogged, or that fuel distributor is not working correctly. You can also do this for a particular length of time and measure the output. There is a spec for this but I can't remember it right now. Have to look it up.

As a couple of others have mentioned, you can just unplug two injectors from the intake and swap them and see if the plugs change color. Since this is a continuous system it doesn't matter which fuel line goes to any particular cylinder as long as the line reaches.

[Marwil]

@ Paulporsche - When I was running CIS that is very similar to what I did to clean the injectors. I am now running EFI, so running electronic injectors. I can test fire the injectors using my Megasquirt ECU in test mode. It may well be that the injectors are bad.
When I pulled the plugs earlier I did note, and tighten, the screw on tips that the spark plug wire ends clip on to - some of them were quite loose. It stared and idled well, I'll see how it runs once we get dry weather again.

Mark

[Paulporsche]

Got it. Missed that you have megasquirt.