I've been battling with an intermittent problem on my 01 Tacoma for the past 10k miles. Most days it will work ok, some days the idle speed will be 1,000 k RPM when in Neutral (MT) and not moving, and around 2,000 rpm when in neutral and moving...
I replaced the A/F sensor and O2 sensor since I was at 153k on the stock ones anyways. I also replaced the spark plugs, wires, PCV valve and grommet, cleaned the TB and IAC and MAF and air filter during my 150k mile maint. All to no avail, it came back a couple days ago...
I even checked the TB resistance values, and IAC and they all appear normal, with no check engine light. I also checked the dashpots and all are ok. If I apply a vaccum to the rear most dashpot when the truck is idling high, the truck still idles the same.
On the Scangauge, I notice that when the truck idles normal (700 rpm +- 10 rpm), the ignition timing is at 12 degrees. The truck runs in Closed loop, and while moving and in neutral (like coasting down a hill), or even coasting down a hill in gear, or if my foot is applying a lot of throttle the truck will run in open loop.
When the truck is idling high, the truck never drops into Open loop unless I'm on the gas hard. Coasting while moving, it will run in closed loop. I also noticed that the timing is around 28 degrees when the truck is idling high.
If the truck is running normal, and I apply some throttle pressure, the timing is still around 12-13 degrees.
I disconnected my battery, and jumped the two cables and left the key in the ON position for a day in an effort to reset the ECM. It didn't matter, still was there...
I have a feeling something is causing my timing to advance too much, and is causing my truck to idle high. What would cause it?
An idea is the AC switch. If the AC switch is sending a signal to the ECM that the AC is on, how does the ECM raise the idle? Same with the power steering switch. Does the ECM use timing to raise the idle, or the IAC?
Any more advice? Truck runs fine in high idle, it's just VERY annoying.
I replaced the A/F sensor and O2 sensor since I was at 153k on the stock ones anyways. I also replaced the spark plugs, wires, PCV valve and grommet, cleaned the TB and IAC and MAF and air filter during my 150k mile maint. All to no avail, it came back a couple days ago...
I even checked the TB resistance values, and IAC and they all appear normal, with no check engine light. I also checked the dashpots and all are ok. If I apply a vaccum to the rear most dashpot when the truck is idling high, the truck still idles the same.
On the Scangauge, I notice that when the truck idles normal (700 rpm +- 10 rpm), the ignition timing is at 12 degrees. The truck runs in Closed loop, and while moving and in neutral (like coasting down a hill), or even coasting down a hill in gear, or if my foot is applying a lot of throttle the truck will run in open loop.
When the truck is idling high, the truck never drops into Open loop unless I'm on the gas hard. Coasting while moving, it will run in closed loop. I also noticed that the timing is around 28 degrees when the truck is idling high.
If the truck is running normal, and I apply some throttle pressure, the timing is still around 12-13 degrees.
I disconnected my battery, and jumped the two cables and left the key in the ON position for a day in an effort to reset the ECM. It didn't matter, still was there...
I have a feeling something is causing my timing to advance too much, and is causing my truck to idle high. What would cause it?
An idea is the AC switch. If the AC switch is sending a signal to the ECM that the AC is on, how does the ECM raise the idle? Same with the power steering switch. Does the ECM use timing to raise the idle, or the IAC?
Any more advice? Truck runs fine in high idle, it's just VERY annoying.