Surging idle after coming to stop

So a few weeks back I got a 2002 3.4, automatic with about 123k, on it. After putting about 700 miles on it, lately I've noticed that when I'm at a stop light with my foot on the brake I'm getting a slight rpm surge. From about 500 to 1000 rpm real quick, just enough to get my attention and make me press the brake harder. Issue only happens maybe 60-70% of the stops and its long after the truck has come up to temp. Have only noticed this with AC running, haven't driven yet without AC running to see if issue still exist. Oh also, just so you know, the check engine light is not activated if that matters.

I'm out of town at the moment and just looking for suggestions of things to look into so I'm prepared when I get back home. Any suggestions would be appreciated.

 

How old are the spark plugs?

 

Not sure at all to be honest. I can see the past 10 years of service records every 5,000 miles on the Toyota "my vehicle" site. I don't specifically see anything about plug replacement on there though.

 

Let's start there than, shall we?

 

A/C compressor engaging and disengaging. Completely normal.

 

That is what I was hoping, my only concern with this is that I have only noticed this within the past 150 or so miles of driving. When I first got the truck, I did a 600 mile road trip with the ac on the whole time and never noticed the issue. Granted I did a lot less stopping at stop signs and red lights, so I could have just overlooked it. Next time I get a chance I will drive without the ac on and see if the issue can be replicated.

 

IAC valve perhaps, or possibly the fuel pump going bad can cause a surge at idle.

 

Oh and yeah, if this is happening when the AC is on then it's just your AC compressor

 

Thanks, for the suggestions. Tomorrow I'm going to drive around without the AC to eliminate it just being normal compressor behavior.

 

Drove about 50 miles today with no AC, the idle surge never happened. Glad it seems appears to be normal behavior. Feel kinda dumb but never experienced that with my two previous vehicles.

Thanks for the help everyone.

 

Totally normal. Mine does it as well and has for the past six years. Normal.