crankshaft sensor and cyl #3 misfire HELP!!!!

[HTX86chevy]

My truck is acting up..... it takes about 2-4 tries to get it to crank up and run.... aslo when I press the gas to move forward or reverse it is acting up like it is deprived of GAS. I took it to the autoparts so they can scan the codes and they said:
1.) 2 front o2 sensors need to be changed cuz its running too lean
2.)crankshaft sensor is bad
3.) cylinder #3 misfire

I recently changed 1 front o2 sensors about 3 weeks ago should i also change the other?
where is the crank sensor located anyone have a pic???
what would cause misfire on one specific cyl?????? anyone have the firing order so i can identify the #3 cylinder?

oh yeah, its a 2001 gmc sierra 1500 4.8 automatic
i also changed all 8 spark plugs 3 weeks ago but didnt change the wires cuz they were too expensive lol

[bighaas79]

It's gonna get real expensive if you follow the parts store and buy the parts they say you need only to discover it isn't fixing the problem. You need to take it somewhere that can properly diagnose it. If you don't have access to a scanner and know what you are looking at to be able to figure out whats wrong, all you can get from here is guesses. If it does need a crank sensor you should do a crank position relearn which requires a scanner anyway.

[usmcchevy]

I agree, it needs to be properly diagnosed. However It never hurts to change the fuel filter which needs to be done anyway. Pull the vac hose off the fuel regulator and see if you have gas in the hose, if you do replace the fuel regulator. I'm guessing you have a fuel issue which is causing it to run lean and miss fire.

[HTX86chevy]

well. i replaced the crank sensor, added new plug wires and it seems to be running better. However, when you first crank it up it takes awhile to gain "power" . I'm thinking the fuel sending unit is acting up.... I can hear a buzzing sound from the tank when the truck is acting up and when it smooths out after a few minutes the buzzing sound goes away.

Fuel Pump???

also it drives smooth once it warms up but when you smash the gas it will only gradually pick up, but still picks up speed

[usmcchevy]

Fuel filter, check the fuel press reg then check your fuel pressure to see if its the pump.

[HTX86chevy]

where can i find the fuel press regulator? i will need a gauge correct?

[HTX86chevy]

ok, i managed to locate and check the fuel pressure regulator. its fine
fuel filter is also fine. I will check the fuel pressure as soon as i get the gauge to do so.
any more ideas??

[HTX86chevy]

fuel pump is fine, im getting enough fuel pressure so now im eliminating fuel issue as the problem.....
had the codes checked again and now since replacing the crank sensor and 02 sensor I am only getting one code: cyl 3 misfire.

The vehicle picks up quickly when im about 1/4 - 1/2 on gas pedal but if i smash it , it seems to lose power..... what causes a misfire. I have replaced spark plugs and wires already. could the spark plug on cyl 3 be defective?

[truckdude239]

sounds like a blown intake gasket to me 4.3 and 4.8 are bad about blowing the intake gaskets

[HTX86chevy]

when you mention intake gasket are you talking about the intake manifolds or the very top portion of the motor?

i think i came up on some info about spraying something to see if it runs better?
how would i go about this?

[truckdude239]

lower intake not upper can spray it with cleaner or start fuild it see if it smooths out