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Discussion Starter #1
Not strictly Alfa related, because Alfas are specced with NGK plugs, but has anyone had issues with Bosch spark plugs in any application?

I have had some running issues with my Puma, and on looking at the plugs, two of them were suffering from cracked insulation on the external side.


They had only been in the car for 2000 miles.
 

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Discussion Starter #3
I have had running problems with the car for a while now. i fitted a set of HT leads and a replacement coil, and the car was ok for a while.

Then car had become pretty much undriveable. Thinking the problem lay elsewhere I replaced the lambda sensor, MAF, throttle position sensor as well.


It seems like the new HT leads masked the problem for a while..
 

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Yes, we used to offer Bosch spark plugs as a cheaper option in TS engines (correct size and grade) and we had quite a few failures so we have stopped using them. We had 4 customer's engines replaced under Bosch's warranty on the plugs and an engine in one of our courtesy cars, after part of the spark plug fell off and dropped into the engine. We checked all our stocks and found one faulty brand new spark plug, where the insert was already loose:

New plug:

YouTube - ‪MVI 3846‬‏

Failed plug removed from engine:

YouTube - ‪Broken Sparkplug‬‏

Bosch have since discontinued that specific spark plug.
 

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Discussion Starter #5
That is shocking, I will post a picture of mine up tomorrow, but it is the "cold" insulator that is badly cracked.
 

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I have read elsewhere about the Bosch's efficiency reducing much before that of NGK in many different applications. Personally would swap out for NGK.
 

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From personal experience it appears there are still a number of Bosch plugs out there which are outdated/ or have withdrawn still in circulation? I recently replaced a set of Bosch in her machine which had been performing OK for about 17,000 miles, only to find they were no longer available, so I went the NGK route.:):
 
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