New coils solved rough idle/low rpm stuttering (1 Viewer)

[BamaHoo]

This may be of help to someone in the future--I've been troubleshooting a rough idle/low rpm stuttering problem with my 2000LC for a couple months now. The problem manifested while stopped and in drive and very occasionally while driving at low rpm uphill (where it would feel like a bucking sensation that I would then accelerate through). I got this truck in November, and replaced the spark plugs pretty early in ownership. When I replaced them, the coils visibly looked fine, indeed fairly new-looking, although it was clear that they were aftermarket/not OEM (except for one Denso-stickered coil). The coils have no identifying marks I could find, although I haven't taken a magnifying glass to them. I had no codes thrown on the OBDII and no CEL, but I had a persistent rough idle while stopped in drive (fluctuating RPMs with a sense that it might stall out), taking off from a stop, and very occasionally I would have a bucking sensation going up certain inclines at a lower speed (where I could "power through" it by giving it gas). I had cleaned the MAF, replaced the vacuum hoses, replaced the fuel pressure regulator, and had ordered a fuel pump (arrived yesterday). Also replaced the charcoal canister and associated hoses. But, the issue persisted. After running a few ChatGPT-aided searches of posts on this forum, bad coils kept popping up as a possible cause. So, I ordered a full set of Denso coils from RockAuto that I installed this past weekend, and now after four days of driving on them and with the idle settled back down after the ECM reset, I think I can safely say that it was the coils. Not a hint of the problem anymore.

I do still need to do the valve cover gaskets (no current leak, but they require re-torquing often), solve the clunk/thunk, a slight windshield leak, and I'm sure other things, but at least I now feel like it may be worth it to tackle these other issues with a much better running engine.