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Spark Plug condition diagnosis help

Old 12-20-2018, 11:35 AM
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Spark Plug condition diagnosis help

RESOLVED: The Bosch D3 injectors needed a custom tune (the engine otherwise 100% stock). They were far richer than the advertised 19lb. The final calibration had them around 24 lbs. Special thanks to Scott Hansen who stuck with it for eight iterations. Finally passed smog with flying colors. Powertrain runs (and smells) like a new car. Thanks for all the help everyone.

Pulled these out of my stock LB9 with peanut cam after about 1500 miles. They were brand new then. The previous set of plugs, also had fouling on cylinder 2 after about 1,000 miles.
Bought the car with 117,00 miles a couple years ago. Passed smog the first time, running as it was when I bought it. This last time, it failed and smelled rich and running a little rough. Was also throwing a Code 13. I will check the O2 circuit and ECM grounds. The engine is consuming coolant in small amounts but no leaks. So I dove into the intake manifold suspecting leaking rear coolant ports but it doesn't appear to have been the case. As part of the effort, I replaced the plugs again and found them like this. The Coder 13 and this plug may be unrelated as cylinder 2 is not on the O2 sensor side.

Does this look like oil or coolant contamination? My guess is oil but I am not an expert. The car doesn't smoke (much). Hard acceleration a little.




Last edited by Tootie Pang; 02-11-2019 at 12:17 PM.
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Old 12-20-2018, 11:41 AM
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Re: Spark Plug condition diagnosis help

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Old 12-20-2018, 12:29 PM
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Re: Spark Plug condition diagnosis help

Looks like oil to me.

What kind of condition was the gasket across the bottom of that intake port in? (move the camera over and take a pic of that port)
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Old 12-20-2018, 12:30 PM
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Re: Spark Plug condition diagnosis help

I am no expert either but that white residue on the electrode sure looks like calcium on that # 2 cylinder. The overall condition looks rich, the plugs should be tan not black.
When you pulled the previous set did they look like these? There are alot of things that could cause a rich condition.

I had a ElCamino that had a bad head gasket and was burning coolant in the cylinder, It would leave a calcium deposit on the plug as it burned water. That deposit would build on the plug over time. Had no clue until I told this old mechanic and he told me what it was.
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Old 12-20-2018, 05:32 PM
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Re: Spark Plug condition diagnosis help

Thanks Gents. Here are the pics, SofaK. The bottom two with the stuffed ports was before cleaning.






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Old 12-21-2018, 07:02 PM
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Re: Spark Plug condition diagnosis help

Compression numbers? That does seem like oil fouling.... just replaced all the plugs on my 86 LB9 and all were a tan color. My compression numbers were 190 across the board.

Didn't you say in another post that you already replaced the stem seals?

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Old 12-21-2018, 08:53 PM
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Re: Spark Plug condition diagnosis help

A bit off topic but The coolant ports in the rear of the head look horrible, like mud.
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Old 01-01-2019, 12:04 AM
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Re: Spark Plug condition diagnosis help

Perform compression and if possible leakdown tests

use a very high quality compression tester. Not a rental. Try to use two different compression testers if possible. Write the numbers down and use a decimal. Repeat the test several times to be sure.

What you want is every cylinder to report a very similar number. If some are exceptionally high its probably oil in the cylinder. Oil in cylinder increases compression ratio and leads to detonation this way. If a cylinder reads low you can at least tell there is a huge hole somewhere.
Its easy to guess that a couple of your cylinders either need rings or have a broken piston somewhere, passing oil
If not, then it has to be getting in somewhere, the intake ports and head ports would be oil soaked/trails of oil. Which I am not sure I can see.

It would be nice if there were some head gasket leak causing it. But water leaking in doesn't cause oily black goop looking plugs.
Also as other have said the engine does not appear to be tuned properly. You want a nice white to tan looking plug usually. And clean.

Last edited by Kingtal0n; 01-01-2019 at 12:07 AM.
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Old 01-01-2019, 03:09 PM
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Re: Spark Plug condition diagnosis help

The #2 plug electrode was somehow destroyed. Those white specs could be aluminum. You can buy USB inspection cameras for your laptop/tablet for less than $20 and I think you should take a look at your pistons through the sparkplug holes. Car is running very rich indicated by the sooted plugs. So I think you have multiple problems. That lifter valley looks pretty filthy so the motor may have had some excessive blow-by or just plain lack of goof oil & oil changes.

Sorry for the bad news.
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Old 01-02-2019, 05:26 AM
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Re: Spark Plug condition diagnosis help

That number 2 cylinder spark plug looks like a different plug compared to the others. Besides being destroyed, look at the close up pic. the ground strap is angle cut compared to the other plugs which are square cut.
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Old 01-04-2019, 05:48 PM
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Re: Spark Plug condition diagnosis help

Happy New Year All! Thanks for all the exceptional wisdom. I am going to take a close look at that No. 2. It does look different.

Also, SofaK, I did recently do the valve stem seals.

FWIW, the engine was running fine a year ago, I then did a Seafoam soak spraying into the intake manifold into the cylinders and letting it sit for a few hours as well as added to the gasoline and it seemed to start running funny after that. Can that stuff fail rings or should I forget about that?

I would do the compression test, but those plugs are so dang hard to get to.

The oil is done regularly with Mobil 1 high mileage.

Sure does look like oil in there.

For some reason the engine is running rich as well, fuel pressure, vacuum, all good, so that should get cleared up with a custom tune I am doing right now.

Any shop recommendations in the Los Angeles area? Preferably around Glendale/Burbank/Valley. I am thinking I should take this to an expert for a reality check.

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Old 01-04-2019, 06:58 PM
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Re: Spark Plug condition diagnosis help

C'mon man. Compression test isn't that hard. Usually the hose makes threading it in easier than the plugs.

I haven't seen that SeaFoam does anything useful besides help free up really nasty lifters (when used in the oil). It's basically lighter fluid and I think a high idle water treatment would probably do more good.

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Old 01-05-2019, 07:58 PM
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Re: Spark Plug condition diagnosis help

I know GD but I've changed the plugs three times in the last year and my neck muscles and forearms are shredded!! Not an attractive proposition right now. I just installed a plugged EGR valve and will have the tune remove the EGR function so it should pass visual and still be clean from the tune. I finally got a good run of data and we will see if the next tune improves the rich running- BLMs and INTs are just over 100. Then I can pass smog and then think about compression tests.

Also, plug 7 is similar to 2 but not as bad.
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Old 01-06-2019, 06:36 PM
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Re: Spark Plug condition diagnosis help

If I have a car with plugs hard to access...

I modify the vehicle to make the plugs easy to access.

Its literally the first thing I consider before purchasing or swapping a high power/performance oriented vehicle.

Because plug condition is... at least at first (test and tune for custom configs) "everything"
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Old 01-27-2019, 01:09 PM
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Re: Spark Plug condition diagnosis help

So after eight tune iterations, the engine is perfect. Scott Hansen did the programming. I will pull the 2 plug later and inspect. It was running very rich with the Bosch D3 injectors. The car runs perfect now, like a new one. What a difference.

and to recap what I think happened from the start:

Late 2017, I was trying to chase a poor idle. I replaced the original Multecs with D3s. At the same time (which I should not have done), I found the timing set was waaay sloppy and replaced it. The car then ran great- for a short while, then started downhill. I put the Multecs back in but by then the plugs were fouled but I didn't realize it so I dismissed the D3's as the culprit and the rest is history. 14 months of wondering what was wrong. Grounds, EGR, O2 sensor, ECM, intake manifold gaskets, MAF, geez its endless. Should've tried to tune it first thing.

Last edited by Tootie Pang; 02-11-2019 at 12:18 PM.
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Old 01-27-2019, 02:14 PM
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Re: Spark Plug condition diagnosis help

Congrats and thx for sharing. It's common for owners to install different injectors not realizing how it can affect the tune. What is common is the problem occurs shortly after the owner changed something on the engine and doesn't realize it.
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