20 Most Recent 1991 GMC Sierra Questions & Answers

You will get your solution and all info on service info, repair info, parts info, wiring/electrical/fuse diagrams, error/fault codes, torque specs, PCV,
owner's/service/repair/parts/maintenance manuals etc everything
this website www.reliable-store.com
it's a very good website for vehicle problems even as old as 1991 ford..

1991 GMC Sierra | Answered on Mar 19, 2018

Remove the blend door motor and move the door by hand. Blend door motors are cheap. Why not just replace it?

1991 GMC Sierra | Answered on Dec 05, 2017

Could be the controller. Check the vacuum line from the engine to vacuum ball. then from the ball to the controller. Vacuum is what controls the vent actuators.

1991 GMC Sierra | Answered on Oct 30, 2016

Under the dash near the floor there is a panel that moves to divert air where you select it to go. Some are vacume controled and others electrically controled. Some times it is just an actuator at this module that is bad and you just replace it.

1991 GMC Sierra | Answered on Nov 23, 2015

That info is on the internet-- for decades
& in hundreds of places

All you have to do is google the questions,
for pictures,descriptions,etc

You Tube Video- is always were you go, also

1991 GMC Sierra | Answered on Jun 26, 2015

Sounds like a bad fuel pump.

1991 GMC Sierra | Answered on Jun 22, 2015

check wires from sender make sure they are not broken pinched grounded out i had this same issue with my 89 3500 454 and the wires were rubbing the balancer finally wearing through grounding them this told the computer there was an issue with oil pressure and blew the fuse to prevent engine damage i traced them out and fixed never had an issue again

1991 GMC Sierra | Answered on Apr 25, 2015

check your rotor arm and distributor cap may need cleaned of carbon build up.and then check your plugs .may be sooty and need cleaned.

1991 GMC Sierra | Answered on Mar 03, 2015

Sounds like a timing issue. Has the timing belt been replaced? They are usually good for about 60K miles, depending on how hard the truck is driven.

1991 GMC Sierra | Answered on Mar 03, 2015

As with most all vehicles, there are small set screw around headlight bezel. One or two on top of core support and often one on each side of headlight. Myself usually wait til dusk or darker park on a flat surface and align beam on a wall having vehicle approx. 6 ft. back.

1991 GMC Sierra | Answered on Feb 12, 2015

Likely electrical issue or bad fuel pump which draws excessive amps when reving up thus blowing fuse and creating drain on electrics making oil gauge reading drop.

1991 GMC Sierra | Answered on Feb 10, 2015

Here, is what I think you are asking. The TBI intake from a 91 will fit the same size engine from 88 to 95. The Vortec didn't come out till 96 I believe. So if your 91 is the original engine then it is not a Vortec motor. If you want to swap your 5.7 with another 5.7 (5.7 = 350) Then the 88-95 should work, Just double check your sensors and locations as the plugs may be different and or in different locations. I know my 88 GMC and my 94 chevy (both K1500's) were a little different. Hope this helps.

1991 GMC Sierra | Answered on Feb 03, 2015

If its a 7004r push it all the way in and then move it 7 clicks out,,, they are very minor clicks so be sure,,, if you dont have it right you will burn up the trans in a few months

1991 GMC Sierra | Answered on Feb 02, 2015

Remove spark plug cylinder #1 place cylinder end of compression time. Crankshaft pulley timing mark at 0 degree
remove distributor cap then find on the cap where is the number 1 cylinder
while placing distributor in place place rotor to face cylinder 1 wire
replace cap and wires
start engine and move dist. to the best rpm then with timing light adjust timing
hope it help

1991 GMC Sierra | Answered on Jan 20, 2015

These symptoms usually mean you have a failed main or big end bearing in the engine. If it gets more noticeable as the engine warms up, that type of failure is even more likely. If the knocking varies with revs it is more likely a big end. You may be able to get the sump off without pulling out the engine, and do an inspection.

I can't think what the brake warning light would have to do with all that.

1991 GMC Sierra | Answered on Jan 13, 2015

That fuse feed the whole dash. You have either a bad sending unit in the tank or a bad wire. Rarely does the gauge itself go bad.

1991 GMC Sierra | Answered on Dec 30, 2014

Unfortunately, theae are common problems. There is more than likely a bad circuit board. Most major auto part stores carry these.
A thumbs up would be greatly appreciated if this answer is helpful to you. windshield-wiper-zb4bomd1rt4qms0dqd12kkt2-5-0.jpg

1991 GMC Sierra | Answered on Dec 20, 2014

Ignition 'Spark' present ??

If you need further help, reach me via phone at https://www.6ya.com/expert/ralph_2f0886b7d6af32ce

1991 GMC Sierra | Answered on Dec 11, 2014

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