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1991 Toyota Pickup intermittant idle issue

Tiny
CELTICRIDER
  • MEMBER
  • 1991 TOYOTA PICKUP
  • 4 CYL
  • 4WD
  • MANUAL
  • 168,000 MILES
My toyota pickup has an intermittant idle stumble. I have replaced the spark plugs, plug wires, pcv valve, fuel filter, air filter, thermostat, cooling fan, temp sensor, cold start injector sensor and nothing has helped. After driving for awhile, sometimes when I come to a stop the idle will sit at 900 and then quickly drop to 400 - 500 then slowly climb back to 900, then repeat over and over again. Any ideas what to do next?
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Monday, January 12th, 2009 AT 10:03 AM

3 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
Hi celticrider,

Did you try to retrieve for Diagnostic Trouble Codes?

Was the Check Engine Lamp showing?
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Wednesday, January 14th, 2009 AT 9:56 AM
Tiny
CELTICRIDER
  • MEMBER
  • 2 POSTS
There is no engine lamp on or codes present.
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Wednesday, January 14th, 2009 AT 10:01 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
The engine uses a Air Flow Meter and the symptoms you described could be due to
1. Vacumn leakage between AFM and throttle body.
2. Valve clearances too tight.
3. Idling speed adjusted too high. Idling speed should be 750 rpm at operating temperature.


https://www.2carpros.com/forum/automotive_pictures/192750_IdleScrew90Pickup_1.jpg

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Wednesday, January 14th, 2009 AT 10:37 AM

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