1990 Other Toyota Models erratic idle

1990 TOYOTA
110,000 MILES • 4 CYL • 4WD • MANUAL
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JOHN QUINN
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  • 1 POST
I have a 1990 Toyota pickup with four-wheel drive, a four cylinder engine and a manual transmission.

When I first got the truck when I started it cold the rpm would idle a 2000rpm. As the engine warmed the idle would slowly drop to 750rpm. I assumed this was normal.

Lately the rpm starts at 2000rpm but never drops below 1200rpm. The rpm constantly cycles between 1200 rm and 1500 rpm with the brake off.

When the brake is applied the rpm drops 850rpm and then cycles between 850 rpm and 1150 rpm.

other than this the engine runs good.
May 26, 2008 at 11:49 PM
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BMRFIXIT
  • ASE Certified Mechanic
  • 19,053 POSTS
  • ASE Certified Mechanic
Check throttle plate make sure its free and closing
remove and clean idle air control valve very possible for it to be full of carbon and other stuff
May 27, 2008 at 6:11 AM
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