Diesel-like sound

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Oct 20, 2010
Central NJ
I've noticed a sound that I can only describe as diesel-like from my wife's 97 LC. I notice it when hitting the throttle from a stop, when the truck shifts between gears, and when gassing it while moving even w/o any fear changes. It's a rather brief sound, maybe 3 to 5 seconds. Sounds like marbles rubbing together. I do not notice it when driving at a steady speed - its not constant.

I just need a starting point to start troubleshooting what it could be. It runs fine and even seems to have more get-up-and-go than my 96.


Sounds like pre-ignition to me, but I don't know much about gas powered 80's.
Maybe check the timing??
I've had something that sounds similar - if I run 93 octane fuel with an octane booster additive it doesn't seem to happen - I have had the entire top end cleaned - no help - plugs, wires, cap, etc - still happens with regular fuel - I just live with it for now but would love to figure out what it is...
Timing is my best guess but have not checked it yet
Check that timing!
I've never checked the timing in a vehicle before. Time to read the FSM again for a how-to.

Kernal, I got your PM. When I bought the truck, the seller included a box of new OEM parts he hadn't had a chance to install yet. One is a new T stat. I don't want to read into it, but maybe the engine is really running hot. The temp gauge on the dash shows good temp, but I do know how "vague" it is. I've got a ScanGauge II in my 96, and just hopped on Amazon.com and ordered one for my 97. So if it's running hot I'm gonna find out tomorrow (I'll switch my ScanGauge to the 97 tomorrow).

If your air intake hose has a leak, that will cause it as well. The intake hose should not be rock hard (or cracked).
Is the timing not automatically managed by the ECU? Maybe you can check it, but I didn't think you could set it. Ignition timing is reported by the OBDII scanners like scanguage.
AFAIK the FSM method is that you manually set the timing (3' BTDC for the 1FZFE), then the ECU adjusts it from there depending on the data it receives. Wait for the experts to chime in for a better explanation.
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Pretty sure it's the timing. I still need to find a timing light to actually check it, but I notice a difference in the position of the distributor on my wife's 80 (the one in question) and mine.
Also, ScanGauge reports solid temps in the low 180's either highway or around town. So, not overheating.
To see if it's preignition (or ping) without any special tools you can use some high octane fuel to see if the noise goes away.

Run tank til almost empty. Way past the gas light on solid. Like gas light on solid for 30+ miles. Put in 5 gal of high octane like 94 chevron.

If the noise is gone or significantly reduced you should have your timing checked by a qualified tech. I usually suggest bringing beer if you want it done for mostly free :)
Well I had this sound and 2 days ago I took off a rotting heat shield from one of my catalytic converters. Pinging 'like' sound gone. This was an easy fix for me, I hope it lasts. Also got rid of what I thought was a squeak behind the dash.

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