Running problem with 16v

I have an 89 jetta gli that has been running very poor recently. It seemed to idle a bit rough, and it would also run with very little power. Like the mixture wasn't right. I took it in to a shop and they said that a good place to start would be to replace the oxygen sensor that wasn't functioning. So I did that, passed my emissions with flying colors and it ran awesome. I drove it home and it was fine, but then the next day when i tried to start it, it ran great for a while and then it just turned like crap again. It had no power, and would drop rpms when you would come to a stop. Now it alternates from running good to complete crap randomly when you start it. I have no idea what this could be. any help is appreciated. thanks

an 89 16v should be CE-2 wiring with CIS-E fueling so that eliminates some of the common problems found in the 90+ 16v Motronics.

when u said it ran good for awhile - how long was that? there is a warm-up cycle timed by the white sensor on the drivers side of the head. There is also a brown sensor that is a cold start time sensor.

the o2 sensor controls the DPR (differential pressure regulator) on the engine bay side of the fuel distributor. It is possible to have a defective O2 sensor....

have you checked for vac leaks? even a cracked dipstick tube can create a problem. More common are the cracked lines etc.

last item to check is the ISV (idle stablilizer valve) which is mounted on the drivers side of the head towards the front.
Listen for it to hum when you turn on the key. If it doesn't, you can try to remove it and clean it with a good carb cleaner - shake it etc till only clear cleaner comes out. Then plug it in again and turn on the key - if it still doesnt hum - replace it.

it ran good for about a mile or two...

it ran good for about a mile or two...

did you let it run at all before you drove it a mile?

LMK what you find when you check the items on my list.

no i didn't let it run before i drove it. i actually just went back to school, so i don't have my car here to work on it and try your list of things. I have tried two different brand new o2 sensors, so it wouldn't be very likely that that is the problem. i never did check for vac leaks...not sure exactically how to either. the orange connector on my dipstick that is about two inches and connects the tube and the stick actually is loose, and will pull out when i take out the dipstick. i will not be able to check the ISV for a couple of weeks until i go back home. i appreciate the help

the orange connector on my dipstick that is about two inches and connects the tube and the stick actually is loose, and will pull out when i take out the dipstick.

that means its broke - they're cheap on e-bay or less than $5 at a dealer.

you may also want to disconnect the white coolant sensor and see if it runs. I have 2 90 gli's that won't run with it connected - even with new sensors. Still trying to work that one out...

thanks for the help. i will try all of that when i get home