Ok all,

I have fixed my surging idle once again. This a super common problem that is on this website all the time. I have had the problem many times since I got my 850 and I have fixed it several different ways per suggestions on this website. However, I have never seen all the answers in one place, so here is my comprehensive look at the problem. This time, all I had to do was take off the idle air control and spray it with air intake cleaner. A bunch of black crap came out. Once it is clean, the little spindle in there should spin back in forth with very little resistance. I now plan on cleaning this thing once a year along with the flame trap and the throttle body.

There is good discussion on this website of how to clean the IAC but no mention of where it is. The idle air control is found at the front right corner of the engine block, just left of the battery. It is under a small cover and is hooked up to two vacume hoses. The IAC is a 4 inch long metal tube in the shape of a T.

So to summarize, if your 850/S70 has a surging or erratic idle or if the car is stalling as you let up on the gas along with many of the dash lights coming on, try these steps:
1. Clean IAC as described above (free)
2. Clean battery terminals (free)
3. Clean flame trap and at the same time throttle body.(free)
4. Check voltage on battery with car off (12.5 volts), on battery with car on (13.8-14.6 volts) and on alternator. (free) This should also point to if you need new plug wires if you are losing voltage.
5. New spark plugs ($20)
6. Replace fuel pump relay ($35 and easy)
7. Replace Throttle position sensor. This is a small electronic part that controls the butterfly valve on the throttle. When it gets old, it doesn't open and close the butterfly right.
8. Replace shifter position sensor aka gear position sensor aka transmittion position sensor ($45). Believe it or not the car will stall, not start, die etc if this thing goes bad. Various lights and engine codes will also happen. This often is accompanied by your traction control arrow coming on for no reason.

Hope you find this helpful.
Good Luck,
850 Tacoma