98 runs rough

i have a 98 that runs fine when in open loop mode but as soon as the code scanner shows activity with the 02 sensor it runs REAL bad.

i just replaced the upstream sensor about 4 months and maybe 6k miles ago.

when the car is started the spark advance on live data keeps going between 8 and 12 degrees and when it starts running real bad it goes between 8 and 20 degrees very quickly.

while running bad i can go and tap the distributor with a hammer and will usually resolve the poor running, but sometimes it will continue to run rough until it is done with whatever it does.

if it goes into closed loop mode while driving it bogs down really bad and feels really gutless.

is the new o2 sensor bad already or is the distributor gone south? or any other suggestions?

thanks!!

Tapping on the distributor and relieving the symptoms is a red flag. I think something is either wrong with the distributor or something inside of it.

thats what i thought but didnt understand why it would only do it once it got into closed loop mode. are there sensors in there that only activate when in closed loop mode?

There is one engine management sensor inside; it is the camshaft position sensor. But I'm pretty sure that one is active in closed or open loop.

But gotta look at "cause and effect" principle. If tapping on the distributor changes your symptoms, I'd be thinking about swapping it out.

Several years ago my '98 was having the same symptoms (stumbling and no power) and finally died not too far from home....
Towed the Jeep home and found the problem to be the distributor shaft bushing had gone bad and the shaft was wobbling inside which caused the CKP to ground out on the curved trigger plate and the engines ignition to shutoff....
I would recommend you remove the distributor cap and crank over the engine to see if this is also your problem... Since this happened to mine...; I have heard of a few late '97s and early '98s with the same problem....