I’ve got a 98 with 170k miles and it was running perfectly fine. Started to idle ever so slightly rough and threw a code up for a Bank 1 Side 1 o2 Sensor. Replaced that. Nothing changed. Just kinda left it because I only drive it once a week. And it’s slowly progressively got worse and has thrown more codes. Currently getting codes for Bank 1 running lean, cylinder 1 and 6 misfire, random cylinder misfire, and the VSC code is getting thrown. It runs fairly smooth still besides when idling at a stop or staying around 1500 rpm’s. But over 2k it is still smooth as butter. Accelerating is also smooth with no hiccups or delays. Also the frequency of the rough idle is inconsistent. Sometimes it will chill out and stay steady at about 500-600 for like 30 seconds and then go back to bouncing all around between like 400-700. Which makes me feel like it isn’t a vacuum leak and most likely an electrical thing. Same with it having smooth acceleration and running perfect above 2k and anywhere inbetween besides 1500. I preemptively ordered a VVT solenoid thinking that might be the issue but after more research I have no idea if that is what I need especially since it isn’t throwing a code for VVT. I also have not gotten it vacuum tested yet but I can’t hear any hissing anywhere or anything. Just hoping someone might be able to throw some ideas my way, anything would be appreciated.

 

i would start at the misfire and get a handle on that first! move coils around to see if the problem follows the coil.
if the problem doesn't follow, check your spark plugs thereafter. also do a visual check for frayed wires or broken or disconnected vacuum lines.
at 170k, the plugs should have been replaced at least once.

 

Yes for sure start with the simple things as opposed to a parts canon. Simple tests as suggested, diagnostics. I would also clean the MAF sensor if you haven't already, just need the proper MAF sensor spray cleaner. The 98 you can clean it. Hard to say what it is exactly at this point.

 

If you also have delayed AT shift problems. I will check the air mix path first.
https://www.clublexus.com/forums/ls-...w-ac-on-3.html

 

what were the codes?