Surging idle between 500-800 RPMs?

Tiny
JOEYJOL75
  • MEMBER
  • 2003 TOYOTA AVALON
  • 3.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 240,000 MILES
Mostly on cold start and worse with any climate controls on. I’ve replaced the Idle Air Control Valve and the throttle position Sensor. I’ve removed the throttle body and completely cleaned it and replaced it with new gaskets. The vehicle doesn’t seem to have a purge valve solenoid. Instead, it has several vacuum air switched on an air vacuum manifold directly above the fuel rail. I used alligator clips to power and can hear all three switches clicking when I apply power, so I believe they’re working. I have no check engine light. I used a smoker to try to locate any vacuum hose leaks. I had a small leak in the rear of the car on the charcoal cannister. I fixed that but still have the issue. Also, if I fill the vehicle with gas, it does a rough start. Other than that, it drives fantastic. Help please!
Saturday, April 29th, 2023 AT 7:38 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

When you replaced the IAC, did you make sure the passages were clear? Did you check the air assist hose for leaks? See pic 1 below.

This sounds like it still could be a vacuum issue. Take a look at the remaining pictures below. They are the diagnostics (general) related to the IAC/Idle speed control issues. Let me know if you have already tried these checks.

Take care,

Joe

See pics below.
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Saturday, April 29th, 2023 AT 8:53 PM

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