Okay so, yes, spark plugs are supposed to be pre-gapped. However, I bought really cheap $3 spark plugs off rockauto, SKP brand to be exact. There was no vacuum leak created when replacing the plugs. I believe, for a brief moment, I changed the gap from .044 back to .038 since thats what the old ones were gapped at (which by the way is what I'm trying to emphasize, if the problem was a vacuum leak i may have introduced or anything in regards to changing the plugs, that doesnt answer the question as to why the original plugs were gapped wrong). This lasted for less than a day because, while working with my mechanic friend, we were waiting around for something, so we decided to do some preventative maintenance and clean out my throttle body and replace my PCV valve (although my old PCV was fine and I wish he had left it with me so I had a backup just in case, but whatever its an inexpensive part). After all that, when driving my car, around 20mph the car would hesitate/stumble, like it was losing power, and then it would kick back and kind of jump. It wasn't the transmission because while it happened, instead of the RPMs going up, they were going down. My friend told me the issue was my plugs which I had just changed the gap on, so I decided to say screw it and just put the original plugs back (being a new "mechanic" or car enthusiast I didn't know the importance of using OEM plugs at the time I ordered them) and it didn't solve the issue. I did the idle relearn process a few times as well and it still didn't solve the issue. I live in Las Vegas and it was like 112 degrees that day. It turned out the issue was the heat and that I had less than a quarter tank of gas, I believe the car would lose power because it stopped getting fuel for a second or two. I read online that nissans had this problem, but I'm not sure if it's a nissan-specific problem or if it's a problem with the new fuel pump I just installed which isn't exactly a real quality part or well known brand, but whatever, I'll just fill up the tank every time it gets halfway now. And, re-installing the original Denso plugs that were inside my car when I bought it, seemed to bring my gas mileage which before was as low as like 12mpg, to currently an average of about 22mpg. However, like I said, the gap on these plugs is at .038 not the factory .044. I made sure to check the gap on a new gapping tool at autozone to verify my tool was giving the correct reading, both gapping tools gave the same measurement. And, I had went to the junkyard and pulled the plugs on an altima there around the same year as mine, and the plugs measured about .044, so basically factory spec. After cleaning the throttle body and doing the idle relearn process, my car no longer starts at 1500rpm and drops to 750 once its warmed up, it seems to start at about 1000rpm. So I guess at this point...here's my question..
Should I take the original Denso plugs out and gap them to .044 then re-install them and see what happens? Or, since my gas mileage is kind of back from the dead, and that's the way the plugs were gapped when I bought the car, should I leave it like that?
Any advice would be greatly appreciated. I'm kind of already assuming you guys are going to want me to re-gap them to factory spec and see what happens so we can try and get an idea as to why they were gapped wrong in the first place and also make sure im not doing any damage to the engine or ignition system from leaving the plugs the way they are...
Thanks everybody!
~Vince