How crucial is having the right gap and what is the range of difference that is lenient enough to pass? I have a 2004 Prius and the NGK Iridium spark plugs all came with the gauge reading .040 but the Amazon page of the product said "Notes: Gap 0.44" and it does confirm that it fits for my vehicle. Should I adjust it? I have the gap gauge tool but do't really want to take a chance messing up the copper centre electrode
Toyota’s Repair Manual (more info) gives the specifications for the spark plug gap: Standard: 1.0 to 1.1 mm (0.039 to 0.043 in.) Maximum: 1.2 mm (0.047 in.) It advises, “If the gap is greater than maximum, replace the spark plug.” DENSO recommends, “Do not adjust the gap of a plug that has a thin electrode, such as a platinum plug or an iridium plug, because this may result in damage to the center electrode.”
^^^This and Some times the Amazon or other websites have wrong in fitment info Also when you are about to install the sparks you should just very carefully measure the gap. Although they are pre-gaped you may have 1 or more sparks that are out of specs and then get a new one that is correct. By measuring them you make an insurance against manufacturer error
Amazon? The #1 source of Chinese counterfeits in the world? (or is that eBay?) I would have concerns that you have may purchased Chinese counterfeit spark plugs. Search the forum for the topic. They're everywhere and will probably start misfiring at around 30k miles instead of 100k plus miles like a good Denso SK16R11 I have the gap gauge tool but do't really want to take a chance messing up the copper centre electrode Now I'm really confused...it should be an iridium fine wire tip center electrode. Every manufacturer recommends to not adjust the gap on a fine tip iridium plug. Those plugs should have had a hard cardboard tube installed over the threaded portion, and it should extend past the ground electrode to protect the tip. If they were all .040, there's really no reason at all to not leave them as is, rather than risk damaging the fine wire tips. yessir. I adjusted it to .043 thank you well done?......You're totally overthinking this....and adjusting it to the max end of the spec makes no sense..so now the gap is harder to jump and as it wears, the gap will be out of the spec range sooner. If there is a range (ie .039-.043, you want the gap to start at the small end, so as it wears, it will take longer to reach the big end.
The plug manufacturers these days design a plug, and the gap. And you can pretty much guarantee out-of-the-box everything is as it should be. If the gap is off, something is wrong. More'n likely, your logic.
