1990 FIREBIRD

  • Tiny
  • flamenbird87
  • 1990 Pontiac Firebird
  • 6 CYL
  • 2WD
  • automatic
  • 160,000 miles

On my 90 firbird 3.1 V6 it idles rough after warm up but drives in the higher rpms fine has a little surging while driving. But bad gas milage.I checked all vacum lines. Nothing leaking.I checked timing and it was at 16 before I adjusted to 10 btdc like book says with wire uncliped but when I reconect wire the timing jumps back up to 16 to 20 before tdc and surges between 16 and 20.I took off my egr and sprayed it out but no difference any ideas?

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Sunday, December 26th, 2010 AT 9:50 PM

10 Replies

  • Tiny
  • rasmataz
  • Member

Check the fuel pressure if okay, clean out the idle air control valve, test the throttle position and manifold absolute pressure sensor-

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Sunday, December 26th, 2010 AT 9:59 PM
  • Tiny
  • flamenbird87
  • Member

Thanks for the help, where is the idle air control valve, and the manifold absolute pressure sensor located?

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Monday, December 27th, 2010 AT 12:16 AM
  • Tiny
  • flamenbird87
  • Member

Ok I found the IAC valve and cleaned it put it back on no change. Still looking for the the manifold absolute pressure sensor

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Monday, December 27th, 2010 AT 1:39 AM
  • Tiny
  • rasmataz
  • Member

The MAP sensor is on the right side of the firewall

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Monday, December 27th, 2010 AT 9:30 PM
  • Tiny
  • flamenbird87
  • Member

Thanks for the info and diagram this will help.I cleaned the IAC valve and check it it does work I took off my intake duct to the throttle and cleaned the butterfly asymbleI adjusted the timming again but when I did the timming I uncliped the single wire by the firewall the round wire connector not thee rectangle one and it droped the idle I then set timming to 10 degress before TDC but as soon as I reconnected the wire. The idle went up a little and the timming jumped to 12 to 16 again don't understand it the fuel pump is new so don't get this any ideas?

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Tuesday, December 28th, 2010 AT 5:01 AM
  • Tiny
  • rasmataz
  • Member

Try adjusting the throttle stop screw to drop the idle speed

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Tuesday, December 28th, 2010 AT 6:15 AM
  • Tiny
  • flamenbird87
  • Member

I will try that, thanks

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Tuesday, December 28th, 2010 AT 6:24 PM
  • Tiny
  • flamenbird87
  • Member

I droped the idle speed and it is at 600 when idling, Maybee I am diconnecting the wrong wire when I time the car. There are two single wire connectors one is rectangled and by the coil, the other is more by the firewall and closer to the fan motor and a round connector that is the one when I disconnect it my idle goes down. The rectangled one I disconnect and nothing happens to the idle. Wich one is the corect one?

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Wednesday, December 29th, 2010 AT 6:04 PM
  • Tiny
  • rasmataz
  • Member

You have to disconnect the EST wire and then you check the ignition timing

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Wednesday, December 29th, 2010 AT 9:33 PM
  • Tiny
  • flamenbird87
  • Member

Ok, Thanks for the reply, By any chance do you have a diagram that shows where it is located or the color of the wires, (wire diagram)?

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Wednesday, December 29th, 2010 AT 10:05 PM

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