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I changed my spark plugs back in the beginning of October along with some other things at about 91,000 miles. Afterwards, instead of a smoother cold idle and better gas mileage I noticed the car seemed sluggish. I thought maybe they were gapped wrong and wasnt even sure if that would matter much. I also read about spark plugs coming lose so tonight I went back in to see if they were tight and took them out to check the gap. I also read the NKG gaps are supposed to be .44, well I took them out and found this.
Could the gap change since I installed them??
So i changed the gap to this.....
Not sure if that will make any difference since its still within spec. I went out for a drive and it seemed fine, will have to see if it still seems sluggish over time. Any thoughts on this from anyone?
Also I forgot to mention my gas mileage seemed to go down after originally replacing the plugs. Can the difference in gap cause that much issue?
Yes! Straight from NGK
DO I NEED TO SET THE GAP WHEN INSTALLING A NEW SET OF PLUGS?
A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a preselected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy and accelerated plug wear. It is always best to check the gap against the manufacturer's specifications. If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium, be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode.
Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".
FYI, the Service Manual spec for gap is 0.39 - 0.43. Unless things have changed, the NGK's should come pre-gapped at 0.44, which should be fine. FWIW, I've changed plugs twice now (105K and 210K) and I've never found a single NGK mis-gapped, much less all 6 mis-gapped...
Which NGK's did you buy and where did you buy them from?
I knew they came pre-gapped and therefore assumed they were correct and did not check them before installing (wont do that again). I got the NGK 6994 {#IZFR6K11} Laser Iridium plugs from Rockauto. All 6 that I pulled out were gapped what was shown in the first pic I posted above, I guess about .037. There is no way the gap could have changed that much in a 1000 miles right? So i guess I can assume that they were gapped wrong to begin with?! Well I am hoping that I got them gapped correctly and things will be ok.
I too changed mine two weekends ago, bought the NGK Laser Iridiums from Rockauto. Assumed they were pre-gapped so I didn't bother to check. The package on it does say to not manually gap them. The old plugs looked fine, had 160k km on it, but after changing, the car does seems to run smoother, quieter, and with a little more power.
Well, I dont know if its the butt dyno or not but after correcting the spark plug gap the car feels like its peppy self again. I am happy about that because I was concerned what could be wrong and not enjoying the car as much. Not sure on the gas mileage yet because I havent gone through a tank, also got new tires so that may play into it as well.
I believe NGK iridiums are pre gapped. Manually gapping those spark plugs will ruin them. I recently changed my spark plug with those and had no problem whatsoever.
I believe NGK iridiums are pre gapped. Manually gapping those spark plugs will ruin them. I recently changed my spark plug with those and had no problem whatsoever.
Yes they are supposed to be pre-gapped, but as I stated they were wrong for me, how that happened no idea, but i manually gapped them and they were fine. You are wrong that manually gapping them will ruin them. NGK states you can gap them as long as you are careful. https://www.ngksparkplugs.com/about-...w-set-of-plugs
I am about to change the plugs on my 12 TL and the NGK's were .039-.040 so changed to .044 with my old feeler gauge tool and double checked with coin gap tool they are right on. Hoping it will be issue free.
11-20-2016, 05:54 PM
