problems ive had, i had loss of power (stumbling of the engine) SES would come on after 15 or so minutes of driving, was jerky at times but driveable, adn getting worse, i got diagnostic not to long ago and was 5 volts weaker on drivers side o2 than pass side, so i thoguht maybe that was it, changed etc (this is after longtubes are installed...ran fine w/ longtubes for about 2-3 months)


ran PERFECT for about 15 minutes , high way, got off parked at friends house for 30 seconds (left car running) backed out driveway, kicked it, 1 stumble at 4k rpms, consistantly, came back parked for 10 minutes, went t ogo home, never felt such a jerkin/stumbling etc wasnt driveable parked, crunk back up 1 minute later, jerked jerked i tryed to come home, it backfired said service engine and ran fine till i got home (fine as in still stumbled but was back to old tendancys (loss of power etc)

 

i need help

 

You need a scanner and/or to log some runs to see what is going on.

 

i got it scanned and it said "no trouble codes"

 

but why would changing o2 sensor to a new one make it run even worse?

 

i know a lot of people on this board hit these kind of probs with this, but have you replaced your Opti recently? Also, how about plugs/wires? I had a '93 Z28 that acted basically the same as your '94 on 2 different occasions. 1st time it ended up being the plug wires. i started the car at night and and looked over my wires in the dark and had like 2 on each side arching! wasnt good! replaced the wires and the car ran great for a month and it started again. wires were fine that time, but had the car scanned and it showed NOTHING on the computer scanner. so i figure, its Opti time. Replaced the Opti and sure enough, it was my culprit. Either way, good luck and let us know how things go.

 

He's not talking about a "code" scanner... he's talking about a scanner that can monitor the vital engine sensors, and some of the PCM's calculated parameters. TTS DataMaster for OBD-I, AutoTap for OBD-II.

Many engine problems show up as "O2 sensor faults".... but often that is just the symptom, not the cause. Misfires go a long way toward screwing up the feedback from the O2 sensors to the PCM. Ditto for exhuast leaks, and leaking injectors. Once that feedback is corrupt, the PCM loses effective control, and the problem that is causing the misfires in the first place is made even more obvious, or joined by other malfunctions.

You need to look at more than "trouble codes".... those are only the tip of the iceberg.

 

i had burnt wires after headers, so i changed them went fine, later this happend....havnt changed opti, put new plugs in along with headers