1997 Infiniti J30 is sometimes very slow to get power after a full stop, otherwise fine

Question

My 1997 Infiniti J30 is sometimes very slow to get any power when I start going from a full stop. I can put the pedal to the floor, and it will slowly creep forward for 3-5 seconds, then suddenly gets enough power and picks up speed. It only does this sometimes. On some days, it will have perfectly fine acceleration. Other times, it will be slow like this right off the bat. In some cases, it will work fine for part of the day, then start being slow after a couple hours.
Previously, it's engine timing was way off, and it had a bad o2 sensor. I replaced the sensor and had the engine timing fixed (w/new belt and water pump as well).

I thought it might be spark plug related but I can't figure out why it would be bad for hours on end or good for hours on end at different times. I would think a spark plug problem would be consistently bad or good. My theory is that the ECU is still used to trying to work with the bad timing, and needs to be reset to relearn the right air/fuel ratios. (I don't know why it wouldn't be bad all the time though, so maybe it's something more than this) I can't find specific directions for how to fully reset the ECM for this make and model anywhere, including a service manual I found online. I have tried the method where you turn the diagnostic mode screw on the ECM, and the method where you take the cables off the battery and hook them to each other to drain the voltage in the system, and a couple other "This always works for all cars" methods found online. The problem doesn't go away.
Thank you in advance for any ideas or suggestions.

Answer 1

I know this is an olde post, but I've had my '97 for several years and I think it's a year specific issue. Actually I've come to believe it's not an "issue", but rather programming. I've had all J's starting from '93 up and they all lay wheels like no ones business. My best friend has a '96 I sold him and it never does this, neither did my '95 or '94. If you look at the throttle cover it's very different from all previous years. I've been working on this problem for about 4 years myself. Me and Infiniti have done everything and at 200,000 miles all the checks come back perfect on my Black Mamba. She has the same compression as new and all the ohm readouts are spot on. So, to take it a step further when my engine is cold, before the auto systems take over and change the ratios, my car is balls out. Neutral drops and all, burns the tires to the rim. As soon as my engine begins shooting up to operating temp this happens. I'm convinced this is their ancient method of "traction control", basically they have the computer ignore your throttle advance until it can get traction, thus preventing you from spinning out. That's honestly my best diagnoses from the past 4 years of investigation. I'd be willing to bet if you dropped an older computer in it, the "problem" would disappear.