Engine Misfire and OMG Bosch plugs as OE in a GM!

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GMBoy

GMBoy

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Howdy all.

My 2008 Cadillac CTS with the 3.6DI engine started to miss a little under hard acceleration yesterday and the P0300 and P0302 codes came up on my Tech 2. Sure enough, driving it with the Tech 2 connected and running the misfire graphic- it showed severe missing on the #2 cyl.

The car has just turned 52k miles and I was planning on changing the plugs anyhow around 60k miles since I've never ever gotten much more than that out of the OEM plugs. I know some of you have gotten 100k miles, but not me.

Now - I could just take it to the dealer since it is covered under warranty...but being a true BITOGer. I stay far away from dealers and would rather change out the plugs myself than have them only replace 1 plug under warranty.

So....I pull the #2 plug (lucky it is one of the one's you don't have to loosen the intake to get to) and it says AC DELCO 41-990....but it has the Bosch logo and Bosch plug # stamped in the steel part!! WHAT! I said - Bosch plugs in a GM car when so many here say they won't work on GM's LOL. Well- at 52k miles I would agree these plugs are awful. I thought for sure they would be iridium....but are just double platinums. So, I will first be switching coils tomorrow just to be sure it is not a bad coil (in which I will let GM pay for). If it proves the plug is bad, I will change them all out to Autolite double platinums and be done with it. I had also noted a slight miss on cyl #1 with the Tech 2 so I am guessing these plugs are done with and due changing.

Note: I did notice quite a bit of deposits on the plug. Maybe my preventative intake spray clean at each oil change to minimize any potential DI carbon issues fouled the plugs over time. Who knows...
 
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I believe a lot of,if not all AC platinum/iridium plugs are foreign made.AC is not the AC we all knew back in the GM GoodWrench days/"Keep your GM car all GM" days,or heaven forbid the old 60s days when Anita Bryant was pushing in ads for AC filters....
AC Delco nowadays is mostly a brand only and parts are sourced from other companies (like filters from Champ Labs).
 
Originally Posted By: NHGUY
I believe a lot of,if not all AC platinum/iridium plugs are foreign made.AC is not the AC we all knew back in the GM GoodWrench days/"Keep your GM car all GM" days,or heaven forbid the old 60s days when Anita Bryant was pushing in ads for AC filters....
AC Delco nowadays is mostly a brand only and parts are sourced from other companies (like filters from Champ Labs).


That is very true. I was expecting my plugs to be NGK sourced, the Bosch part surprised me.
 
ehhh. My plugs in my saab are NGK. I dont see why if designed "to spec" any company couldnt make them in reality.
 
Originally Posted By: JHZR2
ehhh. My plugs in my saab are NGK. I dont see why if designed "to spec" any company couldnt make them in reality.


That is true. My understated humor was directed at some on here that claim Bosch plugs don't work in GM cars.
 
How do you know its the plug and not a coil or something else? Firstly since it has a warranty I have no idea why your playing with it, but if you feel like it you should have swapped that plug into another hole to see if the misfire follows it.
 
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Originally Posted By: hattaresguy
How do you know its the plug and not a coil or something else? Firstly since it has a warranty I have no idea why your playing with it, but if you feel like it you should have swapped that plug into another hole to see if the misfire follows it.


Please RE-READ my post. I am swapping the coil tommorrow - takes all but 1 minute to remove. As for warranty - they would only replace the 1 bad plug - so why tie up a day waiting at the dealer to do their shoddy work on 1 plug when I can do them all myself correctly. AND I also said if the coil is bad, I would let GM pay since they cost north of $100.

Please READ before posting...
 
Huh makes me curious to check to see what plugs the nox and cruzes came with. My cruze has enough bosch parts on it I wouldn't be surprised if the plugs were bosch too.
 
Originally Posted By: Nick R
Huh makes me curious to check to see what plugs the nox and cruzes came with. My cruze has enough bosch parts on it I wouldn't be surprised if the plugs were bosch too.


The Direct Injection system fuel injectors on the 3.6 are Bosch so I guess they matched the plugs. Not sure about the Cruz. I could look it up.
 
Especially European GM sourced products favor Bosch ignition parts, the Cruze is essentially an Opel Astra just rebranded.

Contrary to popular myths here perpetuated by the NGK viral marketing folks around here Bosch plugs and other ignition parts like distributors, wires, ect, are world class top quality parts that "WHEN USED WITH THE CORRECT APPLICATION" are as durable and dependable as any other brand you'd care to mention, including NGK, Denso, Beru, ect.

The important part is that the correct specifications (application) is used when replacing a part. This is often times the reason why a replacement will fail, the correct replacement application WAS NOT USED. With plugs for eg, you need the correct heat range, electrode number, length, metals, ect.

General rule is that you replace a spark plug with one that matches ALL the specs of the original part. If you do this you will HAVE NO ISSUES 99.9% of the time.
 
Originally Posted By: GMBoy
Originally Posted By: JHZR2
ehhh. My plugs in my saab are NGK. I dont see why if designed "to spec" any company couldnt make them in reality.


That is true. My understated humor was directed at some on here that claim Bosch plugs don't work in GM cars.


Oh I get it. Lots of such claims... and experiences to that point.

Just saying there isnt anything inherently lousy about bosch, if the plug is made to a spec of interest. It is small differences in deviations from spec that IMO cause the issues.
 
Using Bosch Platinum Plus in a GM DIS setup with cause random misfires by 50k miles because of their poorly designed thin electrode being used on an application being fired twice as much with a hot spark. The double center electrodes work quite fine in DIS applications. COP can get by with single platinum/iridium (ie no laser welded button on ground electrode) but GM used iridium instead of platinum on about everything else by this time period. GM even went over to double iridium plugs for DIS engines that original came with double platinum plugs such as the early Ecotecs.

By the way most of the NGK/NTK (ie NGK O2 sensors) production is done here in the US.
 
Originally Posted By: Colt45ws
Waitwaitwait.
You have a Tech 2?
How much did that run you?


Well he does work for GM, so I imagine he probably got a good deal on it, or is borrowing it.
 
Originally Posted By: 91344George

Contrary to popular myths here perpetuated by the NGK viral marketing folks around here Bosch plugs and other ignition parts like distributors, wires, ect, are world class top quality parts that "WHEN USED WITH THE CORRECT APPLICATION" are as durable and dependable as any other brand you'd care to mention, including NGK, Denso, Beru, ect.


Crazy! Per Oreillyauto.com Bosch is OE Recommended Iridium Plug for my Focus and I thought Motorcraft was made by Autolite.
 
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GMBoy,

GM must have some arrangement with Bosch to account for thd double bands on the plug. Funny your no. 2 cylinder has mis-fired cuz I'l getting ready to take my SUV in for the same condition!!!!! For myself I hope it's nothing to be concerned about as I get my Durango ready for my annual trip to Arizonia in about a week. Good luck to you and I'm sure you'll wish the same for me.

Mail Clerk
 
Ouch. Extremely unusual to hear of misfires in a newer car like that with low miles.

Sounds to me like B was likely low bidder. The bean counters will ruin things fast for GM if they force the use of only the cheapest parts.

FWIW I just bought AC-Delco plugs for one of my Savanas and they are NGK iridium. Very pricey, and super long lasting!

Hint, Hint.
 
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