Recommended Spark Plugs run rough?

[Headnsouth]

I just got done chasing my tail on a problem that lasted 25k miles.
Back in 2005 I changed out the plugs on my 98 Pontiac Transport. At the time it had 140k miles and I knew it needed new plugs but if anyone has ever done plugs in one of these they are a PITA to replace at least the back 3 anyway.
I installed Bosch plats in lieu of OEM AC Plats. I figured whats the difference and always thought Bosch made good stuff. Since the installation of the bosch I'd get an itermittent rough idle and DTC for multiple cylinder misfires and specific cylinder misfires that would vary from cylinder to cylinder. The rough idle was similiar to the symptoms I had prior to the plug swap.

Yesterday I swapped out the bosch for the OEM and the van runs smooth again and the CEL cleared. I'm now getting P0420 & p0102 and I'll work on those next weekend.

My question is why do some plugs not run so well in a vehicle they are recommended for? The bosch plugs were regular plats nothting fancy.

[MobileMom]

It sounds to me like those plugs either didn't fit quite right, or they weren't as compatible with your car as they were supposed to be. I regularly by bosch as well, but there have been many times they won't work. Did you replace the wires, cap and rotor when you replaced the plugs? Its good to change your whole spark system instead of just the plugs. This will help it get clean clear spark without dealing with any other old parts. As for the codes that you are reading, as well as the cylinder misfires... Have you tried running some fuel injector cleaner through the car?

[Headnsouth]

The plugs were in the list of compatible plugs for my vehicle as were many different brands. No cap or rotor to replace wires were replaced as well as a coil pak.
The problem was solved after replacing the Bosch plugs. Why they are not suitable is a mystery.

[j cAT]

Originally Posted by Headnsouth

The plugs were in the list of compatible plugs for my vehicle as were many different brands. No cap or rotor to replace wires were replaced as well as a coil pak.
The problem was solved after replacing the Bosch plugs. Why they are not suitable is a mystery.

i use bosch plugs +2 platinum ....and these are on 3 different chevrolet engines.....I have found them to work properly......for 50-60,000mi then I replace them.....BUT there are many that have had the problems you have mentioned......misses/runs ruff.. when you replaced the bosch plugs how did they look if one plug was off color it could have a cracked insulator... if dropped they will crack hard to see cracks.....this will cause a miss..because of your mileage the O2 sensors could be causing those dtc when were the O2 sensors replaced....

you may also have a bad maf with that p0102 dtc and if the O2 sensor is good your looking at a cat gone bad......

[UncleBob]

I make a looooot of money off of bosch plat plus sparkplugs. They are nitorious for causing misfires.

any time I get ANY car in the shop for a drivability complaint, first thing I do is check for bosch plat plus plugs. Its that common of an issue. All the parts stores push the bosch plat plus plugs so I see them all the time.

MOST plug brands and models are pretty decent. I would not hesitate buying any other type of bosch plug. But if you want to avoid all the issues, stick with OE and you'll never have a problem.

BTW, the p0420 is a bad cat. Thats what happens when you ignore misfires too long