1995 5.7L TBI Pinging Under Load

[OBSthebest]

Hey Y'all,

1995 K2500 Light Duty - 111K Miles

Tuned up roughly 9K miles ago. Plugs, wires, distributor. Only use ACDelco when replacing parts on this truck.

Recently, here in Texas we had a cold front that came through that allowed me to not have the AC blasting. LOL

Since it was so quite in the cab of the truck, I noticed around 35 MPH/1600 RPMs and light acceleration (I literally baby this truck), a slight pinging noise coming from the engine bay. I can only hear it when the windows are up and there is no air or radio on.

I'm not extremely mechanically inclined and only have access to basic tools, but would anyone be able to point me in the right direction on what may be the cause?

Thought I would start here before being gouged hundreds of dollars by my mechanic.

I've read here that it may be the EGR valve, but the threads I've read didn't seem to fully relate to this.

If there are any answers I can give to any questions, please ask away!

Thank you!

 

[scott2093]

Would be great if you could get a hold of a scanner and monitor data....knock counts....
Have you checked where your timing is at? I'm not familiar with your year, but if my 93 is advanced a bit too much and I don't run higher octane gas, it'll ping...
truck run normal?
Pulleys can even make funky noises sometimes

 

[OBSthebest]

Yessir, truck starts and runs awesome, idles awesome. I have not checked timing yet.

I may sound stupid for asking, but how would I go about checking that?

I also checked the pullies while it was in an idle and saw a little play in the tensioner, but aren't those supposed to have a little play in them as the belt is rotating?

 

[scott2093]

Yessir, truck starts and runs awesome, idles awesome. I have not checked timing yet.

I may sound stupid for asking, but how would I go about checking that?

I also checked the pullies while it was in an idle and saw a little play in the tensioner, but aren't those supposed to have a little play in them as the belt is rotating?

Well I'll match your may sound stupid by saying I don't even know if checking your truck timing is the same as mine..lol
With a timing light is how I check mine.
Tensioner on mine is pretty stable unless my ac is on. Then it gets a bit shaky. Mine isn't supposed to do that as far as I know. I guess it could depend on how much play you're talking about. They are a fairly common wear item and the tensioner and it's pulley can make a racket as well as the other ones. I wouldn't discount pulleys but you definitely don't want to be pinging if it's really that. Abusive on the motor.
Maybe you can pull your serpentine belt and give all the pulleys a once over. If you don't want to be throwing money away on a mechanic every 5 seconds, consider investing in a decent scanner that will allow you to view live data...

 

[OBSthebest]

Would be great if you could get a hold of a scanner and monitor data....knock counts....
Have you checked where your timing is at? I'm not familiar with your year, but if my 93 is advanced a bit too much and I don't run higher octane gas, it'll ping...
truck run normal?
Pulleys can even make funky noises sometimes

Sorry, please see

Well I'll match your may sound stupid by saying I don't even know if checking your truck timing is the same as mine..lol
With a timing light is how I check mine.
Tensioner on mine is pretty stable unless my ac is on. Then it gets a bit shaky. Mine isn't supposed to do that as far as I know. I guess it could depend on how much play you're talking about. They are a fairly common wear item and the tensioner and it's pulley can make a racket as well as the other ones. I wouldn't discount pulleys but you definitely don't want to be pinging if it's really that. Abusive on the motor.
Maybe you can pull your serpentine belt and give all the pulleys a once over. If you don't want to be throwing money away on a mechanic every 5 seconds, consider investing in a decent scanner that will allow you to view live data...

I will pull the belt tonight and see if that's it. My AC was running at the time of looking them over, so it may have just been that. I will keep this thread posted on what I find after work. Any more information or suggestions is extremely appreciated!

 

[1997]

before going too far, imo, i'd be looking at where you got gas the last time,
87 oct and a top tier supplier? if not try a top tier supplier.

i'd even up the oct to 89 and see how it goes, 1st.

timing is a bit tricky, you have disconnect the brown timing "wire" located behind the glove box on my 95. (you can download the service manual for this site)

Then check with timing light.

 

[OBSthebest]

before going too far, imo, i'd be looking at where you got gas the last time,
87 oct and a top tier supplier? if not try a top tier supplier.

i'd even up the oct to 89 and see how it goes, 1st.

timing is a bit tricky, you have disconnect the brown timing "wire" located behind the glove box on my 95. (you can download the service manual for this site)

Then check with timing light.

I suspected that as well, but when I first noticed the ping, the truck did need gas. I filled up with 87 at Chevron (only pump Chevron or Texaco in all my vehicles), but the ping has continued since.

Thank you so much for pointing me in the direction of the service manual and timing!

 

[PlayingWithTBI]

Well I'll match your may sound stupid by saying I don't even know if checking your truck timing is the same as mine..lol
With a timing light is how I check mine.

That seems to be an ambiguous question - check your "Initial Timing" or reported timing on your scanner. Both are important in troubleshooting KCs. You wanna know the ECM/PCM is seeing the correct Initial timing. You can shine the light on it and watch the change when you hook the EST Bypass wire back up. Then you wanna see what it is when you hear knocking and if it's pulling spark when that happens