It is regarding running issues and heavy sooting up of Bosch spark plugs.
Historically I have tried to stick to OEM original fit parts for all my cars - funds permitting.
So Bosch have been an original equipment supplier to GM / Vauxhall / Opel for years - and to VW too.
Many parts I will only fit the Bosch brand due to inferior other makes.
Okay Rob, stop waffling, cut to the chase...
It would appear that Bosch obtain various spak plugs from Russian or French manufacturers.
It is reported that Russian supplied plugs are the ones to avoid.
Poor insulation quality, excessive sooting up and a service life of less than 3000 miles.
Tests between the plug tip and the metal body have shown resistance values between 10k ohms and 100k ohms.
The resistance should be infinite - open circuit.
Excessive sooting of the plug can make hot-starting very difficult. In extreme cases, the soot is so thick, that the car will not start at all whilst warm.
I have also heard of excessive burning of the rotor arm tip and a weak spark.
The French manufactured parts seem to work perfectly, and to have a much better service life.
So the obvious question - How will I know whether my plugs are Russian or French?
Firstly the Russisn plugs are often very "cheap" to buy.
Always an incentive on these needy cars.
I am told that the country of manufacture should be stamped / etched into the metal part of the plug.
The moral of this is... if your car appears to have any issues with starting and running within 3000 miles of fitting new Bosch plugs....
Check which plugs you have, and if they are the Russian items, swap them out first, before potentially wasting loads of money looking for a fault elsewhere.
