After experiencing a stutter while accelerating at low and high rpms, I changed the spark plugs and COPs yesterday. After putting everything back together, I cranked her up and took her for a test drive. Started fine, let her warm up a bit, then drove at some normal speeds for a bit, tested the RPM range. Then I went WOT. Everything felt super smooth again. No hesitation, no stuttering. Yay.
After about 20 minutes of driving, I started noticing some odd play in the way the car accelerated and decelerated. Sometimes I'd go to ease on the gas from a stop and the RPMs flat line, slightly dip, then spike up and the car would jolt into acceleration. This was not due to a downshift. It was like it was taking a second to think about the throttle input. When letting off the pedal, I would experience a harder than normal decel. Deceleration is normally smooth, this was a little more abrupt.
Then today, when I started the car cold in the morning, it started and RPMs climbed near 2k as normal, then as they came down it dipped all the way down to where the car was almost stalling out, around 100-200 rpms. I let the car die. Started again, same thing, then it would slightly sputter back up to around 600-800 then go back down to 100 while all but stalling. I revved the motor a couple times, only to have it dip way below a 1000 rpms once I let off. Finally after holding throttle at about 1500 for 5-10 seconds, it started to normalize slowly.
Driving normally, I experienced the same thing as yesterday. Delayed input of the throttle from a stop, more abrupt decel once I let off the pedal, mostly while in 1st-3rd gear.
WOT feels great, very smooth, no hiccups at all. I really only experience the delayed throttle intermittently when I'm accelerating from a stop or when I'm beginning to accelerate after braking and slowing down.
I'm at a loss. The only out of the ordinary things that happened were that I drove for a bit without one of my coil cover bolts on. Lost it while replacing plugs and COPs. Had to drive about 30 minutes without it until I could get a replacement. Even then, the coil cover was on, just not bolted all the way down.
Also, I fiddled with my throttle body a bit while I had intake tube off. Pulled throttle a bit so I could see inside upper intake to inspect for build up. I cleaned off the face of the blades with a rag and pulled throttle back and forth to test the play in it.
I'm at a loss. Wanted to give a detailed description as I couldn't find anything of this nature when searching the forums. Saw similar stuff, but nothing exactly like this.
Before anyone says anything about it, it hasn't been that long since I cleaned the IAC, MAF, cleaned and recharged air filter (before I cleaned MAF), replaced fuel filter with bigger 3" filter. All of that has been done in the last 6-8k miles.