I bought Iridium spark plugs for my 2009 S40 2.4i that it's owners manual indicates 0.024" gap for Volvo brand spark plugs.
The Iridium LFR6AIX-11 ( 6619) spark plugs that I bought are pre gap 0.04" , do I need to re gap the Iridium plugs and
if so how you shorten the gap?

 

I always check the gap on new fresh out of the box sparkplugs - regardless of whether they are advertised as pre-gapped.or not. You need a feeler gauge or a gap tool that will press the electrode closer or further from the center.

 

Yes, you should re-gap the plugs to the spec for the vehicle. It's a simple process - I normally just drop the plugs onto a solid surface to deform the L-shaped extension (reducing the gap to the electrode), and then use my handy-dandy circular gapping gauge to bend it back up to the spec. Takes a few seconds a plug once you get the hang of it. The video in the previous reply shows how NOT to use the circular tool (it starts at about 1:45 - just be careful that you don't break the electrode tip).

 

I'm old school with a feeler gauge (going back to my BMW 2002 days with contact points) and then tap the electrode with something metal like a socket to close up to the correct gap or use the feeler blade to widen. Never owned a circular tool.

 

Thank you for tips on adjusting gap.
There are comments on the web indicating Not to adjust Iridium plugs, to start the electrodes are cone shaped with sharp tip. even inserting feeler blade could damage the tip.
Also the Volvo recommended 0.024" is for none Iridium sparks, I was not certain that it applies to an Iridium plug too, that is why I posted.

 

Iridium plugs are only recommended for turbo cars due to the hazards of pre-ignition on a turbo engine. They are really overkill on a normally aspirated engine. They work just fine, but the benefits of the iridium material are not needed. It's a waste of money but hey, it's your money so have fun!

 

1. I bought 6 pack of 6619 (LFR6AIX-11) Iridium Spark Plugs on ebay for $8.99, $1.50 each delivered.
2. I still did not get a clear answer as the recommended 0.024" gap applies to Iridium plugs too, or should I leave them at 0.04" pre gap?

 

I'd reset them to the spec required for your engine and not follow what came out of the box and not over think it. Not all engines require the same gap even though they use the same spark plug model. Spark plugs are designed around thread size, depth and spark temperature range so the plug may fit your engine but the gap should be what the car's spec is. For example, its typical for a turbo to run .028 where NAs run .024. Old school cars (ie cars made in the 70s...) would even recommend a summer setting being slightly wider than the winter setting...

 

Installed NGK IX Iridium Spark Plugs (p/n BKR6EIX) in my 2004 Volvo V70 2.5T AWD wagon (Engine B5254T2 R5 2.5L) with 233,600 miles(replacing Bosch plugs) Thursday afternoon. Within 3 miles of driving car threw P0600, P0863, P0P0571 & P0504, went into limp mode. I restarted the car and cleared the codes and it ran another 4 miles till I got it home. Next morning it prevented starting because of comm failure w/transmission - same codes plus U0073 (bus communication). Disconnected batterie, checked CEM ECU and TCU connections, cleared codes again, reconnected battery and car ran 10 miles without codes. Next morning codes and limp mode returned multiple times.

I called my 2 Volvo specialists and they suspected CEM starting to fail and did not see any relation to new plugs. I decided to bring the car in on Monday but had the weekend to tinker - concerned this might be the end of the vehicle for me ($2k to replace CEM) I decided to remove the NGK plugs and re-install the old Bosch Platinum plugs out of desperation - the problems and codes disappeared. My car has run fine since I removed the NGK plugs and the codes have not returned after several days of driving. Voodoo? Is my car allergic? Do the plugs play a role in CEM communicating to ECU TCU? Ill pick up a new set of Bosch platinum plugs and go my merry way...