Popping sound in air intake

[Pedrofski]

89 SK. 1.6  it makes a popping sound in intake when started,it goes away after a couple minutes but it comes back if I turn on the lights or fan. Any ideas. P

if not backfiring to the intake (bad cam timing , spark timing way off or burned intake valves)

the noise common is ISC there on top see those 2 wires on top the TB>?
if the ISC is bad, it will make noise, they all do  this old.?

but  take it off and hit it with penetrating oil (never wd40)
it is just and air valve modulated 200 times a second after 25 years and 10million  cycles, it gets loose and makes noise. (many posts same)

the deal with HL on blower on or AC on, the ECU raises idle speeds to 1000rpm(or near) and the ECU changes the PWM  modulation on the ISC to raise idle.

so with any change of idle speed, that noise can change.

but be warned cleaning it and lubing it like that, might make more noise. (who knows for sure on old worn out parts)?
good luck on that 89.

That is it. Just unhooked one wire from ISC and noise goes away. Everything seems to work fine with it un hooked is there any reason I can’t leave it unhooked? Thank you much for the info. P