That's the conclusion I've drawn... Pulled my Jeep in the garage last week to fix what sounded like an exhaust leak on the driver's side of the engine. I removed the heatshield and cast into the manifold is the unmistakeable Dorman logo. Apparently this had been a problem for the previous owner. I pulled it off and could see it was leaking from #2 & #6 ports which means its warped. No big deal, used a cutoff wheel to remove the extra casting between the ports, belt sanded it back to flat and then sandblasted it and painted it flat black. While I had the manifold off I pulled the spark plugs just to make it easier to clean the mating surface of the head. This is the first spark plug I pulled...

I've seen some bad spark plugs, but I've never seen one with a hole blasted in the ground electrode! I didn't take pictures of the rest, they were all terrible, gaps must have been like .250" center and ground electrodes all eroded away. As soon as I got this one out, I headed for O'Reilly's to get manifold gaskets and new plugs, picked up some NGK G-Powers and reassembled everything, working great again.

I'm curious how in the world this engine was running symptom free with these plugs? Also, is this a failure due to high mileage or just cheap plugs?

 

IMO.. HIGH Mileage... I have seen plugs with 160K miles and had NO Electrode left..vehicle finally started missing; no power.. wonder why...

 

I guess if there's a plug, it'll run. Factory service interval is 100k and while the engine can adapt to the increasing gap over that span of miles, I prefer to change them more frequently to maintain gas mileage, power, and avoid oddities like that- never seen that before.

 

Many try to replace with "hotter" plugs and wires. From what I've read over the years, that always tends to lead to problems and it's best to stick with the stock Champion plugs and stock Mopar wires. Old tricks often don't work very well with new computer systems. The reason being is the ignition system is monitored by the computer and it will adjust the amount of current shooting through those plugs based on multiple factors and the best way it can do that is when using the stock champion plugs and wires. I would guess they tried to install a hotter plug and/or wires and now the result is seeing fried plug electrodes.

 

Side bar on stock wires- I bought Denso's from Rock Auto and they're numbered (and look identical) to the Mopar wires, without the price tag. They'll be going in with the rest of my maintenance items when that day comes.

 

Travis - did you see a good power and mileage increase after the new plugs? I would have gone with plugs 1 level colder to help stop that

 

Honestly, I could not tell any difference after I replaced them. I mean it was running fine before somehow, I was working on an unrelated issue and decided to check them. We just drove this Jeep 3 hrs away to DFW last month and it ran flawlessly there and back with those janky plugs somehow.

I don't know if the one's I purchased are "hotter" or "colder", I suppose that refers to the gap. I didn't measure them, but they all looked the same, I assume they're all pregapped like every other rare earth metal plug I've purchased in the last 20 years. I like NGK plugs so I pick up a set of their "G Power" plugs which I read are a step up from the "V Power". I hope I did right but from my experience, these engines don't seem to be very picky.

 

Hi Travis, to help you on Heat Ranges: https://ngksparkplugs.com/en/resourc...lug-heat-range In my experience the best spark plug for any engine is the BRAND that was installed by the mfg.. it was the Brand the engine was engineered with to perform at its best and comply with all the warranty and governmental regulations. If your rig is running good and you are happy, I would not be concerned. Get out and enjoy.

 

Thank you for the link on heat ranges, I had no idea, but it makes sense, a hotter plug dissipates less heat to the engine.

As for the BRAND, I'm an NGK fan, but I've also been very pleased with Bosch platinum and Denso iridium, maybe that's just due to my experience with their diesel products. I don't necessarily buy into the "best brand is the OE brand". I think that using the OE specified plug is always a safe bet, sure, but the BEST option? I'm pretty sure that the decision for what plug brand goes in the production engine is decided by someone in a suit, not a lab coat. My example for this is the Volvos I've owned had written right on the oil filler cap "Volvo recommends Castrol" and BMW the same. Do you think that's because Castrol's products are really superior to all other brands, or perhaps did Castrol execs write a fat check to get that printed on there?

 

Not that they wrote a big check.. maybe the best price for the company in all engines. Naturally the blend, additives, & viscosity were fully tested by the engineering team. I know from my 30+ years as a OEM manufacturer's rep that the vehicles performed very well with the OE installed Plugs. Fords on Autolites, GM on AC Delco, Mopar on Champions (Mopar brand are Champion). Don't know about imports; I do know that when it's time mine get the same OE installed plugs. As I always say when asked.. Its your $$ Get What You Want (GWYW).