Low rough idle and idle sticke high at times

COMER

MEMBER
1989 GMC C1500
5.6L
V6
2WD
AUTOMATIC
100,000 MILES

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

6 Replies

HMAC300

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.

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Tuesday, September 1st, 2015 AT 5:54 AM

COMER

MEMBER
3 POSTS

I put a bran new on had lest new injectors fuel pump press check comp check
Thxs

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Tuesday, September 1st, 2015 AT 6:23 AM

HMAC300

MECHANIC
48,601 POSTS

Timing should be at 0 not 2 retard for one thing. Recheck firing order see pic

Image (Click to make bigger)

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Tuesday, September 1st, 2015 AT 6:48 AM

COMER

MEMBER
3 POSTS

Hi checked firing order ok returned to zero still low when hot thx

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Tuesday, September 1st, 2015 AT 8:47 AM

THIS IS MIKE

MECHANIC
686 POSTS

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