Melted Spark Plug Electrodes only on Bank 1.

Jan 14, 2017

As confusing as this may be here's the deal. I had a bad lower intake gasket plus an exhaust leak. This caused my engine to run rich. After I fixed the aformentoned issue with the intake one of the injector pintles came loose from the cylinder 3 injector. I ignored it, placed the pintle in the injector bung and just inserted the injector directly into the pintle and tighten the 4 injector rail nuts down. Heard a noise that I suspect was a vacuum leak and also had a lean condition on Bank 1 and later determined it was the pintle cap not contacting the injector. I glued it back together and the vacuum leak went away and the engine operated much smoother.

All in the midst of this I apparently got some counterfeit Autolite AP606 spark plug form a local parts store.

Engine started running rough at idle again so I decided to pull the plugs and see what was going on. The front bank of cylinders had melted electrodes and and I also noticed all the spark plugs had blued prongs on them. Luckily I had some Bosch R6 Platinums lying around for another project that I cancelled and put those in. Engine runs much smoother now.

Here's my question: Are the melted prongs a product of the lean condition, the plugs being counterfeit or is it both?

Thanks for your input on advance.
Why would you think the plugs are counterfeit?
The logo is riding high on the porcelain instead of around the center near the hex fitting. The material used the make up the autolite and "AP606" were very faint and grey. Almost transparent.
Or are you saying the tip on the ground electrode has worn off? Because that gap looks huge.
Yes I am. It was gapped somewhere between 60 thousandths and 63 thousands. The pointed tip of the electrode has melted and flattened out. It was gapped just enough for the spark plug gapping tool to fit between the prong and electrode
Bear in mind that the 3800 utilizes a 'waste spark' ignition system. Half of the cylinders will have the centerwire be positive polarity and the others will be negative (conventional) polarity. Over time, this difference will cause a noticeable wear pattern that differs depending upon polarity. With conventional polarity the electrode erosion is greatest on the centerwire. Inverted polarity causes greater material loss from the sidewire (ground) electrode.