Running rough at stops

Hi All
I have had my truck into a shop 2 times and no one can tell me what the problem is and has cost me a couple hundred bucks already.
I have a 2001 Tacoma SR 4x4 4cyl automatic.
When stopped in gear the truck idles down and runs rough, it will do this for 15 20 seconds and then there is a click sound and then it idles up and runs smooth for 10 15 seconds then idles down again and this keeps repeating.
No check engine light comes on and it never dies, gas mileage is about normal.
One shop did a tune up, plugs and cleaned something out (not sure what) and one shop did a fuel clean up?? cost me $185.00 I believe he also checked fuel pressure.
But the problem persists. Was told it could be the 02 sensors but again no check engine light comes on.
Any help here would be great !
Thanks
Geri

 

tRY TO LOCATE THE CLICK SOUND. I COULD BE the circuit open relay clicking (basically the fuel pump relay) its mounted up by steering column. Also check the throttle body. see attached file. its for a v6 but I think the 4 cylinder has the same components.

 

Since it comes and goes,,,,,make sure the a/c compressor is "not" coming on. It could be putting a load on and off.

 

I was going to say the same thing, sounds like defrost or A/C is running which will spin the rpms up to normal at intervals.

sub'd for any other info as I chase a low and high idle at times

 

I'm not entirely sure about the clicking sound, but I know a dirty MAP sensor (inside intake) can cause a rough idle. Dirty upstream O2 sensors can cause this too without causing the check engine light to come on. It's happened to me with both a dirty MAP sensor and dirty O2 sensors that never triggered the check engine light. You can clean the MAP sensor with an aerosol cleaner sold just for that purpose, but the O2 sensors need to be replaced if they are dirty. How many miles are on the O2 sensors?

 

Thanks everyone I'll check these out this weekend.
BILLYGOAT I thought about the 02 sensors but from what I've read my gas mileage would be degrading ? I bought the truck used so I'm guessing that the 02 sensors have never been replaced and I have about 113,000 on the odometer.

I have been running premium and plus gas octane instead of just regular, Could this possibly cause the problem?

 

I'm a believer in running what it is tuned for. From the factory 87 octane. If you are in high altitude maybe less, 86 octane.

 

run a couple tanks of 87 or 89 and see if anything changes. I've never run higher than 87 and gas mileage is right on par, not worth the extra money either unless your running a S/C