I just installed a Brand New Subaru Short Block, in my 98 2.5 DOHC Outback. It had 197,000 miles and the head gasket blew.

My question is the dealer gave me NGK PFR6B-11 spark plugs? My book calls for PFR5-11, but they said these are superceded to the 6's???

I've driven it for 200 miles with no problems, until tonight the check engine light came on? Coolant fine, oil fine, seems to be running smooth? Could these plugs be causing issue's?

You need to read the ODBII code. Otherwise it's just a guess.

 

Here's the NGK plug chart code descriptions:

 

I doubt the spark plugs are the source of your CEL. It is highly unlikely that you would have fouled a plug in that short of milage. I use Bosch Platinum plugs in my Legacy OBW with no problems.

 

Pull your codes to see what the problem is. My guess is the knock sensor, or 02 sensor.

Thanks

I pulled the code today, it was P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD. I think the exhaust manifolds needed tightning?

Still wonder if anybody else is using a colder plug? Or is it just my Dealer?

Ah ok. P0420 is purely an emissions code. Typically for soobs it is either the rear o2 sensor, or the front o2 sensor. The front o2 sensor should be an OEM from the dealer. It can also be exhaust leaks. Sometimes people using aftermarket exhaust systems/cats get this code periodically. Soobs are fairly sensitive it seems for this one.

double check to make sure that all the wiring connectors are tight, especially after an engine change. then fronmt O2 sensor - OEM; then rear.

 

i got this code in a 97OBW and it was a loose connection.

An exhaust leak could throw off the ox sensor. If the manifolds were leaking I'd start there.