low rough idle and idle sticke high at times

1989 GMC C1500
100,000 MILES • 5.6L • V6 • 2WD • AUTOMATIC
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COMER
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I start truck revs up than slowly falls to 5 once truck warms up idle goes rough and down to 4 and one time went down below that and thought I could smell raw fuel I have chance every thing I can think of I took it to I mech he said poss valve issue I put new distributor in set timing 2degress retard I am at my wits end

please help
Aug 31, 2015 at 11:34 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
check for a blown gasket at bottom of tbi unit use choke cleaner and spray around it if idle changes then replace it.
Aug 31, 2015 at 10:54 PM
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COMER
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I put a bran new on had lest new injectors fuel pump press check comp check
Thxs
Aug 31, 2015 at 11:23 PM
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HMAC300
  • ✓Experienced Mechanic
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timing should be at 0 not 2 retard for one thing. recheck firing order see pic
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Aug 31, 2015 at 11:48 PM
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COMER
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Hi checked firing order ok returned to zero still low when hot thx
Sep 1, 2015 at 1:47 AM
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THIS IS MIKE
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Hmac300
Sep 12, 2015.

Hi I still can't find out what going on with my truck but today I found out that I have a leaking intake manifold gasket and I had a code that read o2 running rich would fixing that leak stop engine from running rich and stop service engine light from coming on at idle and going off when I drive and low rough idle your thoughts.
Thanks
Sep 14, 2015 at 7:58 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
anytime you have a vacuum leak it will screw up the idle and make run rough due to incorrect fuel mix coming in. the O2 should be reading lean not rich however.
Sep 14, 2015 at 8:27 AM
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