'93 S-10 Problems

Hi,
First of all, Here are the specs:
2.5L 4cyl
5 speed Manual
power nothing..
1993
short box and cab
260,000 km

I just bought this truck dirt cheap and rust free, so I expected a few issues. I've had it for a couple weeks and I've been tackling the problems 1 by 1, starting with a computer change because it was reading jibberish, then all the dash/warning/footwell lights had to be changed because they were all burned out, then a new air cleaner and preheat hose (previous owner had removed it), then last night I timed it and found it was 8 degrees out!, so now it runs a lot better!

A couple days ago I was driving it around and both headlights burned out at once! I tested them and they actually were burned out, so I replaced them, but I'm starting to think this might be an alternator issue. The alternator voltage isn't bad though, its at 14.4 V. Maybe its fluctuating though..

The main problem I'm trying to solve here though is that every time theres no load on the engine (coasting, going downhill...) the check engine soon light turns on. It causes a code 25, which should be air temp I believe. I changed the sensor and it makes no difference. Anyone know whats going on here? The truck definately has character...

EDIT: Forgot to mention when theres no load on the engine but no breaks on, like when coasting, it bumps and acts like it has a bad universal joint, but they're fine. I've heard theres an anti-knock feature that's not working and could be causing this, could that be right?

Thanks,
Eric

When you let off the gas the ECM shuts off the injectors, no fuel to engine. Common with mine to get some bumping as they turn off and on, maybe a bad throttle position sensor or something. Sure help to have a scanner to read and monitor the various sensors to pinpoint the problem. Good old trucks though.

if its air temp, check the flap inside the air breather to nakesure it shuts off from hot air to cool air. it is vacuum operated.

i just replaced the TPS about 3 weeks ago, and uhhhh it wouldnt shift about 3 mins after it started from sitting overnight

If your voltage is constantly higher than 14, your system may actually have burned the lights out, not regulating the charge