Mechanics

HIGH IDLE ISSUE AND INTERMITTANT SHIFTING CAUSE IAC, TPS?

1999 Buick Century • 170,000 miles

Hello, I have a 99 Buick Century and recently I have experienced very high idle speeds and erratic shifting issues. I have cleaned the IAC valve, and did notice my throttle body was rather dirty on the inside. I had cleaned the throttle body with a cleaner, cleaned the IAC, and started the car. The idle was still high. I disconnected the IAC, the TPS, the air box sensor, the sensor on the air intake tube and the EGR sensor, I thought the car should have shuddered or something, so it ran high still. I connected all the sensors back, started the car and still high. My next thought is to disconnect the IAC alone, then the TPS alone. Is there anything I am missing? I have seen others with the same problem, but have not seen any sort of resolution. I thank you for your assistance.
Dennis
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Dlvaughn1963
September 24, 2012.



What is the exact code number its setting now?

Saturntech9
Sep 28, 2012.
Will relay later. Also disconnecting IAC DOES NOT change idle issue

Tiny
Dlvaughn1963
Sep 28, 2012.
If you unplug it it cant change the idle keep me posted.

Saturntech9
Sep 28, 2012.
But how long does it take the computer to respond to the idle setting's return to normal?

Tiny
Dlvaughn1963
Sep 28, 2012.
Shouldnt take that long.

Saturntech9
Sep 28, 2012.
I'm looking for a good diagram for the vacuum lines and don't see one. Besides the one on the hood of the car, is there another one?

Tiny
Dlvaughn1963
Sep 28, 2012.
More info.
When I check the idle with the car being cold the idle is ok, just rumbling, however when the car temp heats up, it goes high. I can't find a leak in the vacuum system unless the leak is at the vac line that runs from the solenoid to the canister, and the canister is in the back of the car. I did a ohms/resistance check of the IAC valve and it checks good unless the valve is just plain worn out.

Tiny
Dlvaughn1963
Sep 28, 2012.
See if the canister purge solenoid is stuck open?

Saturntech9
Sep 28, 2012.
One other has me wonder bout the solenoid, fuel gage doing weird stuff and heavy fuel fumes. Can you tell me exactly how many hoses are connected to the solenoid?

Tiny
Dlvaughn1963
Sep 28, 2012.
There should be the vaccum source from the engine and another hose that goes back to the canister.

Saturntech9
Sep 28, 2012.
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