intermittent low idle and stalling

Hello,
I have 1999 SR5 V6 with 240K miles which I bought new. I have maintained and service this truck myself and take care of it very well. Recently, I have been having intermittent low idle (450-500 RPM) and intermittent stalling, specially when truck is nice and hot with No ck engine light! I have read about the idle control valve and throtle body cleaning and did that last week. The throtle position sensor was replaced 3 years ago, the spark plug wires and plugs were replaced 25000 miles ago 4 years ago. I run fuel injection cleaner at every oil change and replace PCV valve. The fuel filter was replaced 20,000K ago . 3 of the 6 injectors on the driver side was replaced about 5 years ago. Air filter replaced every 15k.

The truck runs great and drives fine but the idle issue is driving me crazy!! Do you guys have any suggestions or experiences with this issue? I ordered the Blue driver OBD2 tool from Amazon yesterday and waiting to hook it up and see if it gives me any more information.

Thanks in advance!

 

Throttle body could need a good cleaning since it’s just idle. The set screw hasn’t changed but maybe enough carbon buildup has occurred that it’s blocking what little airflow is needed for idling.

 

Welcome

 

Thanks guys.....well, I took off the throttle body which was attached to Idle control valve. took the Idle control valve off, sprayed the inside valve with CRC intake cleaner , brush and Qtip , and I cleaned the throttle body with a tooth brush and cleaner and it looked Clean. When I stop at red light, the idle just goes down to 400-500 for 2-3 seconds , then stabilizes . If I let the car Idle, after about a min or so , you can feel the idle drop 100-150 RPM for about 2-3 seconds, close to feel the car about the stall.....Then back to normal again!

Not sure what else could be causing this. Do you thing the Blue driver OBDII may show me more information , with no Ck engine light? Still waiting to get it from Amazon.

Thanks Again!

 

Could it be that your engine ECU is making a slow correction to a sudden load? I would check all of the belt operated accessories: the AC compressor, alternator, and the power steering pump. A belt tensioner pulley may also have developed a catch in it’s bearings…

 

Do these year 4runner ECUs 'relearn' if you remove power? May need to just disconnect the battery and let all the residual power drain and have the ECU relearn its functions after all this cleaning.

 

Did you use a Denso or TOYOTA TPS? If not, then it might be time to replace it again.

The issue is probably going to be in the throttle body. TPS or IAC or a vacuum leak. If you aren't getting any codes, then probably not a vacuum leak, but still worth it to check.

 

They relearn. They run at a high RPM (1500+) until they've relearned and will drop town to 700-800RPM idle after driving around for a while.

 

Something similar happened to me. With the AC on, my RPM would drop very low and surge and usually come up after a bit. I solved it by replacing the entire Throttle Body assembly. I had either a bad TPS or PPS and the ECU simply didn't know where the gas pedal was.

I think it's unlikely, but pulling the belt for each accessory (no serpentine belt on these) and spinning them to check for bad bearings could yield something. Usually they start to whine before really going bad.