Toyota commuter having problems

Ideas greatly appreciated-

I got a 2001 Toyota Echo 5spd (with 200k mi) as my commuter car.. 150 miles a day @ 18mpg was getting to be too much on truck and I figured I could get double that gas mileage, resell when I move closer to work for similar to what I paid for it - end up saving a little cash overall.

I've put about 1500 miles on it so far and have averaged 40mpg, 99% interstate @ 80mph. Zero issues til today.

Decided to add a bottle of Lucas injector cleaner when I was filling up from empty last week. Put bottle in at pump then filled it's whopping 11.9 gal tank. Drove normally for 250 miles.. today though after my 75 mile stretch of interstate on a ramp I noticed it struggling to accelerate, hiccuping I guess. Down shifted and didn't think about it.

Then after work I noticed that it was stumbling at idle, and stumbling when accelerating (1st, 2nd). This seemed to get worse in traffic messing around town, so I got on the interstate and went the 75 miles back home, driving a little harder than before thinking if an injector had been clogged by dislodging something that I'd push it through with some lead foot. No dice, shit was worse when I got off the interstate again, had a good 3 or 4 second stretch in first where it just wouldn't accelerate.

Since it stumbles at idle at a stop (lights dim, almost stalls) I know it's not clutch slipping or anything. I just did plugs 400 miles ago - properly gapped and installed. There was a little oil on plug #1 but not near the electrode when I pulled it. I was careful to not muck it up reinstalling too. No check engine light. Drives great at higher than city speeds.

Any suggestions? All googling has people saying fuel injector cleaner is cleaner burning than gas and probably a coincidence - with something else being screwed up. Since it got worse over the course of my driving today I'd assume it's the fuel (tank has maybe 75 miles left on it, maybe bad mix is even more concentrated?).. tomorrow I'll make sure plugs are still tight and not starting to back out, and make sure coil packs are tight too of course. Really wish she'd just fire a CEL - with how stumbly it was tonight I'm honestly surprised that no light is on... could not rely on car getting you across an intersection safely without possibility of getting tboned from no acceleration.

Long post. My bad. Just trying to throw in some details. Yes I know I bought a bitch car

 

I don't have much advice (or knowledge) for you. I'd say you need fuel, air, and spark to get your engine to work. It's intermittent problems don't sound like an air problem. So, you're left with fuel and spark. If injector cleaner worked last time, that makes it sound like fuel to me. I'd throw a tank of quality 91 octane in it and see if that helps. Beyond that, I'd just check your grounds, plugs and connections to your fuel pump as a precaution. Let us know what you find out!

 

Id fill it up with fuel to try to thin out the additive and drive til she spits out a code or clears up.