How do i tell when my crank position sensor needs to be replaced?

Question

I have a 97' GMC Pickup. Well it's a stick, i drive it down the road it seems as if something is "sapping" the power, like i can have my foot to the floor and it kind "jerks", mostly in 1st and 2nd gear. I recently went up to AutoZone and the guy up there told me it was bad. Anyways, i'm wondering how long i can drive around with it like that before i eventually need to replaec it. Thanks

Answer 1

How on earth would the guy at Autozone know that it is bad? Did he look at it? Or just go off of your description? He's not a mechanic... but he does sell parts!
I'm guessing he checked your check engine light for you... which they aren't exactly well know for their accurate diagnosis, especially with their 50 dollar scanner, but they sure are good at selling you parts until you find the right one.

I would take it to an actual mechanic and have them diagnose it and ask their advice on how long until you need to replace it. But if that is indeed what is causing your problems, you would want to replace it as soon as possible so the problem goes away right? What was the code that came up?

Answer 2

A bad crank sensor shows up as a no-start condition. However, these trucks do not have a stand alone crank sensor as they still have a distributor although not like the other HEI type distributors from older cars and trucks. This one is more of a crank sensor and voltage switch. It sounds as if you are experiencing a misfire on one or more cylinders. The first thing to do is to get the PCM scanned for codes. A crank sensor code could be set by a misfiring motor, so just because a code is set it does not mean that particular part is faulty. A lot of times that is just a clue to what is wrong. The best thing to start to do if this is a misfire problem is pull the spark plug wires away from the plugs and the dist. cap and inspect inside them for signs of corrosion or carbon tracking. If there is any question, replace the complete set. Make sure to check the coil tower and wire as well. Take the dist. cap off and inpsect underneath for carbon tracking as well as the rotor. Again if anything looks suspicious, change it as these are the cheap parts. A partially plugged fuel filter can cause this as well so to be sure, replace it. Next, take all the spark plugs out and inspect for being worn out or having carbon tracking down them. If something is found, replace all after gapping them. If motor still misfires, I would suggest you perform what is known as a power flush of the injection system and to clean the throttle body bore out. A power flush uses a pressurized mixture of clean gas and a heavy duty fuel injector cleaner. You have to tap into the injection port on the fuel rail, disconnect the fuel pump so it does not run, and remove and plug the fuel pressure regulator so as the fuel rail runs at max. pressure. Then run the motor till she stalls as the mixture has been used. Then re-connect everything and re-check. If there is still trouble, you might have a primary or secondary ignition fault which will then have to be diagnosed. Good luck.

Answer 3

I own a shop, and what I would do is replace the throttle position sensor. Another thing that can do this is bad spark plugs, or a worn timing belt/chain. It has all the symptoms of a bad throttle position sensor, a plugged up fuel filter, or injectors that need cleaning. I would do all three, and start with the fuel filter, and then if that don't fix it, replace the sensor. Purchase some good injector cleaner, and add to about 3/4 a tank of gas, and if its the injectors are doing it, it should clear up right away.
Glad to help out, Good Luck!!!

Answer 4

You might have gotten a code for the crank sensor, and if it goes completely out, then the truck will not start..but about the jerking in 1st & 2nd gear, sounds like you might need the throttle body cleaned, or you might have a misfire on a cylinder. Does the truck idle good? If you would email me back, I can tell you things to check, to answer your truck problem...

Answer 5

you have some thing else wrong. the crank sensor tells the coils win to fire. if some thing was wrong with it. it wouldn't start.sounds like the fuel filter needs changing.