What Story Do These Sparkplugs Tell?

[Smoove1010]

My 3.2 sat all winter with a 1/2 tank of stabilized gas. When I drove it last week it ran like it had one dead cylinder. A bottle of Techron, some fresh gas and a new cap and rotor improved things but now she feels like there’s one weak cylinder vs one dead one. I pulled the plugs tonight and found that #5 was wet with gas, the others, if I’m interpreting them correctly, seem to be running lean, but I don’t trust my plug-reading skills. Would very much appreciate some opinions and some suggestions about how a plug could get gas-fouled.

Also noted: #6 has some kind of hairy looking fuzz on it!

I cleaned them all up and re-gapped them, and while she’s idling smoother it still doesn’t feel quite right. Next step may be to get a new set of plugs though these were new when I redid the top end and put new rings in it about 4k miles ago. Thanks in advance for thoughts!
GK

[917_Langheck]

Check that #5 actually sparks when it's supposed to (the wear on the center electrode suggests that it used to work). If it does then then suspect will be an open injector. All the others look good.

[Classic 911]

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[JSV798]

I would suspect the plug lead; measure its resistance and compare with others. You'll need to disconnect it at the distributor end. But could be the plug; I have had new plugs that have turned out to be faulty right from the start. You could also try swapping plugs on, say 5 and 6 and see if the fault moves. Could also swap plugs leads but one test at a time.

Roy

[jma0506]

I'd inspect the inside of the distributor cap for wear as well while you're at it

[proporsche]

you did not mention what are those plugs ?? japanese what?why not use WR7DC plugs....
Ivan

[Smoove1010]

Originally Posted by 917_Langheck

Check that #5 actually sparks when it's supposed to (the wear on the center electrode suggests that it used to work). If it does then then suspect will be an open injector. All the others look good.

I’m thinking something similar. Maybe not stuck wide-open since I’m not seeing any smoke or smelling fuel but in addition to the miss, I’m hearing some small “pops” in the exhaust when I lift my foot off the throttle. That will be my next troubleshooting step.
Thanks!

[Smoove1010]

Originally Posted by JSV798

I would suspect the plug lead; measure its resistance and compare with others. You'll need to disconnect it at the distributor end. But could be the plug; I have had new plugs that have turned out to be faulty right from the start. You could also try swapping plugs on, say 5 and 6 and see if the fault moves. Could also swap plugs leads but one test at a time.

Roy

I can’t rule the plug lead out 100% but the wires were new when I did the top end about 4k miles (and 10+ years(!)) ago, but the car is garage-kept and the wires look like new. Still, that’s a path I may need to follow if my next steps don’t find the culprit.

[Smoove1010]

Originally Posted by proporsche

you did not mention what are those plugs ?? japanese what?why not use WR7DC plugs....
Ivan

The plugs are the NGK BPR6’s. I honestly don’t recall why I went with them vs. Bosch but I’m sure it followed hours of scanning forum threads on spark plugs!

[Smoove1010]

Originally Posted by jma0506

I'd inspect the inside of the distributor cap for wear as well while you're at it

I did do that and I happened to have a new cap on hand. The old one had normal wear but I swapped it out anyway. Not sure if that made a difference or if it was putting fresh gas and a bottle of Techron in that helped smooth it out.

[356911930]

I think your plugs look a little lean too, except # 5. Did you replace the O2 sensor when rebuilt?

Best of luck,

Rahl

[Flat Six]

Originally Posted by proporsche

you did not mention what are those plugs ?? japanese what?why not use WR7DC plugs....
Ivan

Prolly NGK BPR5ES; about 1 heat range hot for a typical 3.2

[Flat Six]

Originally Posted by Smoove1010

The plugs are the NGK BPR6’s. I honestly don’t recall why I went with them vs. Bosch but I’m sure it followed hours of scanning forum threads on spark plugs!

Ah; pic on #1 looks like 5 . . . .

[proporsche]

Originally Posted by Flat Six

Prolly NGK BPR5ES; about 1 heat range hot for a typical 3.2

i just do not like NGK plugs ..period ,..never ever i had a problem with the Bosch or Beru plugs...

Ivan

[Flat Six]

Originally Posted by proporsche

i just do not like NGK plugs ..period ,..never ever i had a problem with the Bosch or Beru plugs...

Ivan

In 50+ years I've never had an issue w/NGKs, ymmv

[proporsche]

Originally Posted by Flat Six

In 50+ years I've never had an issue w/NGKs, ymmv

good to know..i don`t like them anyway....german car with japan plugs;-)
But it makes you wonder who makes those plugs these days..I have seen NGK from Romania , Bosh From Russia, from Israel and India....hardly any from Germany..
Who actually makes plugs in USA??

Ivan

[930cabman]

Originally Posted by 356911930

I think your plugs look a little lean too, except # 5. Did you replace the O2 sensor when rebuilt?

Best of luck,

Rahl

Agreed. can you get an AFR to tell the story.

Lean is not a good place to be

[Smoove1010]

Originally Posted by 930cabman

Agreed. can you get an AFR to tell the story.

Lean is not a good place to be

LMK if this theory makes any sense or if I’m showing my ignorance of how these things work: Based on the theory of a leaky injector, is it possible that the extra fuel and/or un-burned fuel in the exhaust is causing the DME to lean-out the fuel mixture to compensate?
Regardless, I’m not driving the car until I get this sorted out.

Thanks to all for the feedback, much appreciated.

[Smoove1010]

Update: I pulled the right-side fuel rail and checked injectors 4, 5 and 6. They all opened and closed properly on the bench using my makeshift fuel-injector-bench-tester. So fuel delivery seemed to be OK.
I swapped out the #5 spark plug with an old Nippondenso plug, part of a set that was installed by the PO just before I bought the car and which had about 2k miles on them until I did the top-end project and put the stock-spec NGKs in.
The car now runs great, any signs of a weak or dead cylinder are gone, she’s super-smooth running again. I can cruise down the road in 1st gear at idle with nary a bump or a surge. No more chuffing in the exhaust on decel.
So I’m left to surmise that the #5 plug went bad somehow, perhaps by becoming gas-soaked?. I thought that a plug going bad from being gas or oil-fouled was an old wive’s tale, but is it possible that a bath in semi-stale gas killed the spark plug?
Anyhow, I’ll be driving the car regularly (first stop, get a replacement NGK plug) and we’ll see how long the new #5 plug lives underneath an injector with a suspicious reputation.
After it runs a while I’ll see if the plugs still show a lean condition.
Thanks fellow Pelicans for your suggestions.

[junkman300SD]

Originally Posted by proporsche

good to know..i don`t like them anyway....german car with japan plugs;-)
But it makes you wonder who makes those plugs these days..I have seen NGK from Romania , Bosh From Russia, from Israel and India....hardly any from Germany..
Who actually makes plugs in USA??

Ivan

FWIW, I have a 78 Datsun Z and won't use anything besides NGK in it. That's what came factory and I've had very bad results with other brands in that engine.

I am not saying they are best for the 3.2 as I only recently acquired the car and haven't done much work on it (yet). I'll start with going factory in the 911 unless there is a reason to do something different.