89 gmc 1500 350 tbi
Asked by Johnathan Nov 29, 2017 at 08:11 PM about the 1989 GMC Sierra 1500 K1500 Standard Cab SB 4WD
Question type: Maintenance & Repair
I replaced my knock sensor and after that my truck idles
crazy and keeps dying even when I give it gas my egr valve
is fine just need some help any ideas will help
10 Answers
Anywhere in the intake system downstream of the mass air flow sensor all the way to where the intake bolts to the block, it's possible a vacuum line was knocked of or broken while changing the knock sensor. Where is it located on your truck btw?
On the side of the block passenger side in front of the starter
It COULD be faulty out of the box, it's rare but it happens. Could you elaborate on the crazy idle and HOW the truck dies
It turns over and starts when it idles it idles really hi then super low as if it's going to die I try to feather the gas to keep it alive but it dissent work every time I give it gas it wants to die I checked my fuel pump and sending unit and filter it's getting air
That's really not consistent with a bad knock sensor but still sounds like a possible vacuum leak, a large one if so. I can't see your idle air control valve going belly up randomly after changing the knock sensor. I think you're going to find that you have something is unplugged whether it's electrical or a vacuum line. Keep in mind that the pcv valve/ hose and the charcoal (evap) canister/ hoses are potentials for vacuum leaks, I don't know where your specific charcoal canister is located but most older GM trucks have them under the hood close to the radiator
Ok I'll check those things the only reason I change the k rock sensor is because I couldn't pull hills without it wanting to die on me and that's what the code threw at me
I had that same issue with my car (minus the engine light). Because mine is obd2 I was able to watch live data and see that as I was losing speed on hills my timing advance was retarding to the point of base advance (caused by pre- ignition), I started running premium fuel with a higher octane rating and my car has never run better! No more losing speed on moderate inclines =) Carbon deposits that build up in the combustion chamber decrease combustion volume and in effect raise the compression ratio which can cause pre- ignition (not too be confused with detonation). I'm not saying this is your original problem it's just food for thought. I'll try to remember to check in tomorrow night to see how you've made out, good luck to you!
So after replacing every sensor I could think of turns out it was a fuel pump going out
