If it is fuel injectors, you probably would not hear them from inside the car.

I've not opened up the '87, but I think it is the same engine and valve train as my '91. The valves are adjusted by replacing coin-shaped shims that rest in little cups under the cam.

If you have a "feeler guage" (less than $10), you can easily check to see if the valves need adjustment. Check any service manual for method and required clearance, then just warm the car, remove the valve cover and spark plugs, and rotate the engine, checking the clearance between the cam and follower when the lobe is opposite the follower.

Write down the clearances so that you know which shims can be swapped around and what sizes you need to buy. The shims are sold in metric sizes, so if you measure clearances in thousandths of an inch, you'll need a calculator when you go to the parts counter.

Unless the noise is unbearable, wait until you do a timing belt to do the valve shims. You'll have to remove the timing belt from the cam to do this job, so I wouldn't do one job unless I was doing the other.