I have a 91 with a stock 13B. Lately, I have had a noticable variation in idle speeds. After warmup, the engine idles at around 1500 but fluctuates between 1500 and 1650. It is like it has a pulse and is steady. The car runs fine and no problems as to acceleration or cruise. The only recent change I made was to change the filter housing. I had the top cut out of the former and decided to put 1 inch holes in the replacement on the cool side of the housing. Any ideas? Thanks.

And yes, I did try the search first.

 

Anyone.........anyone?

 

Perhaps TPS, did you check if it was adjusted properly? Could also be a vac leak.