1991 Camry clicking and hesitating when accelerating

[KellyGirlKY]

Yesterday morning my dip stick read low and I added about 1/3 Q of oil to my 91'Camry (171,000'miles). When I headed home from work, I noticed a hesitation when accelerating and a clicking noise from under the car. Any idea what this could be?? The oil was an opened bottle I had in my trunk. Does oil go bad?? I'll double check what kind I put in....either 10W30 or 5W30. It's possible I could have put in the wrong oil depending on what they used the last time I had it changed (about a month and a half ago). It could be something totally unrelated to the oil, but it had been running just fine....

[KellyGirlKY]

Just got done at Grease Monkey. They said it wouldn't be the oil. That there is an oil leak, maybe from the valve covers and fresh oil on the back of engine. But that shouldn't cause the hesitation. It only hesitates when I accelerate from a compete stop (I.e., stoplight, etc). And only until I get up to about 25-30 MPH

[Doctor J]

I need to know if it is 4 or 6 cylinder.
Try to accelerate car in park or neutral (M/T) to duplicate noise / hesitation (which will show as a "skip" or "fart" (figure of speech) when revving up
My guess will be an exhaust system, but check for the vacuum leaks, mechanical noise with stethoscope may be needed as well.

[KellyGirlKY]

I'm quite sure it's a 4 cylinder (I think LE) but I'll double check when I go out at lunch.

[KellyGirlKY]

Its a Camry DX, 4-cylinder. Tried pressing on gas while in park - no knocking, clinking, etc. - just normal idling. I drove through town at lunch. I noticed after about 10 minutes of driving, it no longer did it! Getting ready to head back to work. My car was only off for like 5 minutes so I'll see if it goes back to the hesitation and idling