What makes certain spark plugs not work in certain engines?

[Chris142]

We have all seen it. Some engines don't like some plug brands.

Yesterday I removed 4 plugs from an Audi. The ones I removed were NGK double platinums and were put in at the Audi factory.

I installed 4 new Bosch double platinums. I always check the gap very carefully as to not damage the plugs. Don't force a gap tool to fit.

The Bosch were supposed to be .043 but were .015-.025 so I used needle nose plyers to adjust the gaps to spec.

Car came back today with a multiple cyl misfire on all 4 cyls. I removed the Bosch plugs and they got me NGK plugs which I put in and test drove the car with no issues.

What is the difference between plugs if they crossover? What does NGK do different than Bosch or Champion vs AC Delco?

It's not like there are secrets in the plug world.

 

[oldcodger]

Where did you obtain the Bosch plugs? The ones i have installed came closely and consistently gapped.

 

[justalubetech]

Bosch says not to adjust gap on those plugs on their website, it's super easy to damage the electrodes/coating

Everyone in the Honda world says not to use Autolites in pretty much any Honda engine, but I always use them in mine without issue

 

[Chris142]

Where did you obtain the Bosch plugs? The ones i have installed came closely and consistently gapped.

Worldpac

 

[slacktide_bitog]

Did the Bosch plugs say "do not gap" by any chance?

 

[Chris142]

Bosch says not to adjust gap on those plugs on their website, it's super easy to damage the electrodes/coating

Everyone in the Honda world says not to use Autolites in pretty much any Honda engine, but I always use them in mine without issue

That's why I do it very carefully. I can't put plugs in with a .015 gap

 

[Chris142]

Did the Bosch plugs say "do not gap" by any chance?

No. It did say not to force that gap open with the gap tool though. Thats why I use needle nose

 

[Chris142]

Thread 'O.K. to gap double platinum sparkplugs'

Jul 11, 2005

A counter guy showed me a Bosch info sheet that said NOT to re-gap their platinum plug.

I recently purchased some "better" Motorcraft double platinum plugs that are about .010 too small.

Is it ok to adjust the gap without damaging the platinum coating??

Thank you.

• doitmyself
• Replies: 4
• Forum: Mechanical/Maintenance Forum

 

[loneryder]

We have all seen it. Some engines don't like some plug brands.

Yesterday I removed 4 plugs from an Audi. The ones I removed were NGK double platinums and were put in at the Audi factory.

I installed 4 new Bosch double platinums. I always check the gap very carefully as to not damage the plugs. Don't force a gap tool to fit.

The Bosch were supposed to be .043 but were .015-.025 so I used needle nose plyers to adjust the gaps to spec.

Car came back today with a multiple cyl misfire on all 4 cyls. I removed the Bosch plugs and they got me NGK plugs which I put in and test drove the car with no issues.

What is the difference between plugs if they crossover? What does NGK do different than Bosch or Champion vs AC Delco?

It's not like there are secrets in the plug world.

They may be incorrectly indexed. Not your fault, the manufacturers. The open end of the plug is facing the cylinder wall.

 

[BigCahuna]

The only reason I can see why one plug wouldn't work properly over another brand of plug, would be the internal resistance, and or too big of an air gap. You can check internal resistance by using a multi meter. The shorter the air gap, the stronger the spark .,,,

 

[Exhaustgases]

Its been like that since the 1960's, some how all the different spark plug manufactures for their brand of vehicles/ engines seem to work good in said brand. AC for GM, Autolite for ford, Bosch for German stuff, Champion - aircraft and sometimes other engines, NGK and Denso Japan stuff. Don't know what works ok in Mopar, was it Champion that supplied them?

 

[KevinMalone]

I always assumed it was an old myth perpetuated on the internet. BMW specs both NGK and Bosch plugs for the same engines; the only restriction in the FSM is do not mix brands

 

[Jetronic]

We have all seen it. Some engines don't like some plug brands.

Yesterday I removed 4 plugs from an Audi. The ones I removed were NGK double platinums and were put in at the Audi factory.

I installed 4 new Bosch double platinums. I always check the gap very carefully as to not damage the plugs. Don't force a gap tool to fit.

The Bosch were supposed to be .043 but were .015-.025 so I used needle nose plyers to adjust the gaps to spec.

Car came back today with a multiple cyl misfire on all 4 cyls. I removed the Bosch plugs and they got me NGK plugs which I put in and test drove the car with no issues.

What is the difference between plugs if they crossover? What does NGK do different than Bosch or Champion vs AC Delco?

It's not like there are secrets in the plug world.

I don't know why, but I have noticed similar things. Some plugs work better or longer in some applications.

 

[Escape08]

Spark plug types. Cold and hot

 

[willbur]

The only reason I can see why one plug wouldn't work properly over another brand of plug, would be the internal resistance, and or too big of an air gap. You can check internal resistance by using a multi meter. The shorter the air gap, the stronger the spark .,,,

The larger the gap (up to a reasonable limit) the stronger the spark. More voltage to jump= hotter spark

 

[rijndael]

Spark plug types. Cold and hot

That's my thought too. Spark plug tip temp is a important. The tip has to be hot enough to burn off carbon deposits. But, it can't be too hot or you get in to pre-ignition issues. The hotter the tip the small your 'safety margin' is for pre-ignition.

 

[dnewton3]

Gapping plugs is not something that should be done in all circumstances.

For OPE and older applications when using copper core plugs, etc ... gapping plugs is perfectly acceptable.

When using these new style plugs with high-tech coatings, etc, it's best to buy them pre-gapped and then if they are incorrect out of the box, return them and get a different set. Don't mess with trying to regap them.

I don't believe this is a problem unique to any one brand.
And with the proliferation of counterfeits in the marketplace, that's also a concern.

 

[walterjay]

Counterfeit plugs?

 

[Chris142]

Counterfeit plugs?

It's the 2nd time I have had a problem with Bosch plugs. I'm wondering if someone @ worldpac got a good deal on plugs not knowing they were counterfeit

 

[meep]

I liked the Bosch marketing and liked the name and tried their plugs in a lot of cars. Subaru seemed fine with them. We had a VW vanagon which came oem with them. Volvos exuded warmth and happiness. Hondas wouldn’t idle hardly at all with them. I think I put a set in a 4.7 tundra and they were ok.

Everything I’ve owned once the Volvo P2s aged out of my home have done well with NGK/Denso.

HOWEVER - I installed a set of NGK iridiums, sourced through rock auto or Autozone (can’t remember which), which may have contributed to some misfires in my 2.7 ecoboost at 10k miles. I replaced a coil pack after high misfire count, and then that cylinder continued to have misfires. In a pinch I tightened the plug gap a smidge and it then ran fine. I suspected a plug problem. NGK/denso ships oem with the 2.7.