Top 20 1991 GMC Sierra Questions & Answers

Bulbs do dim over time but they shouldn't be 'that' dim. With the engine running. Remove a bulb and use a test meter to test the voltage at the bulb socket, it should be between 12.5 and 13.2 volts. The with the engine off, test the voltage at the battery terminals. It should be just over 12 volts. Then test the bulbs with 2 wires to the battery. Spray the bulb sockets with WD40. Are the back reflector surface of the headlights in good condition? Have you polished off any yellowing and dirt from the headlight plastic lenses?

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..

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

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.

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.

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

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.

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.

You can use Dexron 3 or go to a dealer and get the fluid.

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.

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.

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.

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

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.

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.

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

there is a kevlar heat shield tube that can be used around electrical wires Probable available from an electrical equipment whole sales shop. Next fibreglass matting cut into strips and wrapped around the wire will do the trick. Just do not use epoxy as this is what makes fibre glass inflammable. Best bet is to have an accredited auto electrician make up a battery cable with a length so that the cable can be positioned away from any heat source.

you left info for a 91 gmc sierra no such thing try again

it is ok to by pass the heater core but you will get no cabin heat in cold weather. find the 2 hoses that go into the heater core and join them together. Remember to check the coolant level at the radiator cap as you may get an air lock in the system

Try Rockauto.com