1991 Toyota Corolla 4A-FE will not idle down unless vacuum

Tiny
7A6B9C
  • MEMBER
  • 1991 TOYOTA COROLLA
  • 4 CYL
  • FWD
  • MANUAL
  • 197,901 MILES
Hello. 1991 Toyota Corolla. 1.6 4A-FE, 5sp. Car will not idle down by itself and rpm stays fluctuating between 2200- 1800 rpm. The only time it will idle below 1000RPM is when I disconnect vaccum line from MAP sensor. Swapped MAP- no change. Swapped throttle body- no change. Cannot locate IACV(idle air control valve) anywhere, only thing that resembles it is on the bottom of throttle body which was swapped. Cannot locate an EGR valve also to check. No apparent vaccum leaks anywhere. Suggestions, solution? Thanks.
Monday, November 23rd, 2009 AT 1:00 PM

2 Replies

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
HI there, Using a length of hose, listen around the inlet manifold foe any vacuum leaks, these engines do often suck in the inlet gasket and can cause this problem.

Mark (mhpautos)
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Monday, November 23rd, 2009 AT 4:33 PM
Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
Only CA. Cars had EGR in 91, US and Canada cars did not. IAC is under the TB, has a coolant hose connected.

Two possibilities, vacuum leak or timing.
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Tuesday, November 24th, 2009 AT 7:39 AM

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