Hi
just bought a 96 ls with the 4.3l. I have a click/tick got different answer on what it sounds like. It’s right behind the alternator. Do these have a soft cam or is it a lifter tick? I have no codes and only time it gives me a struggle it’s when I’m at a light for more then a few minutes and all it does is drop 100 rpm’s then goes right back up.

 

It may be a collapsed lifter. Check your oil to make sure that there is no water/antifreeze in it (looks like a milkshake). That is one possible cause. It can be any of the other rotating engine accessories like PS pump, alternator, water pump or AC compressor. An engine stethoscope can help narrow that down, You can buy one or use the old school pipe/screwdriver,tire orin to the ear hack.

George

 

Here is a collapsed lifter only observed when oil was hot - turns out from way too much bearing clearance (low oil pressure at idle) after intake gaskets leaked coolant into oil. Intake leak had been repaired but bearings had not. SES light had been disabled (wire disconnected from cluster and taped) because it was flashing all the time and had set misfire codes. Video taken after driving 130 miles home on the Interstate, right after buying it. Apparently PO did this and then traded for a new vehicle when the problems became really expensive. Only 65K miles, 10 years ago. I learned to always scan for OBD2 codes when buying a vehicle.

 

this!!!