I Know you have already checked & replaced it but go back & look good at the O2 sensor. Mine did the Exact same thing Except for no CEL. I replaced sensor & same thing. found wiring to O2 sensor bad. I repaired wiring now truck running good as new. I also was pulling my hair out. That could be why your machanic was reading O2 bad.

Hope you find it!

 

The black block looking thing is the timing spout, pull it then set your base timing. Then after it's timed put a vacuum guage on to see if you have a leak, I would still look at your ECT because it sets fuel mixture based on engine temperature it could be bad and seeing a cold engine and dumping gas in it to warm it up.

 

Sorry didn't see you had changed ECT, I'm at work and got a bunch of people talking to me all at once. Once again set your base timing with spout unplugged then take a vacuum reading that will tell you if your cat is bad or you have a leak. also make sure you didn't fill your lower end with gas this can at minimum thin out your oil and ruin your bearings or at worst blow up your engine. never mind EGR until after timing and vacuum.

 

EDIT - apparently I can't tell a 6 from a 7. I didn't notice this was from last Feb, but hey maybe there is some follow-up.

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I don't mean to thread jack, but can someone post the EXACT location of the spout connector on the 88' 2.3L, or a picture. Any description I have seen on here or even in the manual is vague at best. I thought I knew where it was, now I don't think that was even it.

billynjuls - I feel your pain. I have NEVER seen the CEL on my 88', and I don't think it even exists. Anyway, if you get a cheap code reader $20 - $30 you should have a plug over on the passenger's side by the firewall. If you look over by the hood hinge and the heater hoses there is an odd shaped plug tucked under the fender that plugs into the code scanners.

I have been having some similar issues with my 88' 2.3L. I have not started my own thread yet because I wanted to replace the TPS like you did since mine threw a bad code for it, and I have had no time to do some other basic diagnostics.

Mine sputters mostly if you drive it, park, and get back in after a few min to go again. It will idle fine for the first few sec, then when it seems the sensors take over, I will have to pump the gas to keep it going as it spits, sputters, and backfires through the intake. After that it will idle normal. It will also lose most of it's power once it is fully warmed up. I can hardly maintain any kind of speed going up a hill, and accelerating feels like I am towing another truck behind me.

I am interested to see what you find, because like you, most of the sensors are new. I did a mini-rebuild on the engine last year, and have been tracking down little issues ever since.

 

lol Thats funny replying to a year old thread and not realizing it! Was the issue ever resolved billynjuls? I had the same sputtering problem and lower gas mileage early last year myself, tho not as low as you're saying. Just like a 4 mpg diff. I had just changed my plugs, wires, cap, and rotor and managed to switch cylinders 2 and 3 on my 3.0 V6. There was NO code to be pulled, and anyone I talked to pointed in the direction of all sensors montioned. But the end all fix was checking my firing order that's printed on the intake manifold.