Pinging alot with 89

Xxl2

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Truck is a 91 c 1500 4.3. I need to check my timming this thing pings like crazy on 89 octane. It dose it when the engine is under more load. My question is do i have to disconnect the vacuum advance before checking the timming? Any good videos on this?
 

PlayingWithTBI

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My question is do i have to disconnect the vacuum advance before checking the timming? Any good videos on this?
You shouldn't have a "vacuum advance", you should have a black/tan EST bypass wire you disconnect to eliminate the ECM from changing timing while you check to ensure it's on TDC.

Here's where the connector s/b in your truck. You may have to dig inside the wire loom to find it.

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Xxl2

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Thanks I 'll start looking. Now I have the general aera
 

evilunclegrimace

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Check your fuel pressure after you verify that the timing is correct. Low fuel pressure can cause the engine to ping under load.
 

PlayingWithTBI

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There's a lot of good ones on the market. I'd get one with the advance feature so, you can see how much the ECM is advancing the timing too (when the EST bypass wire is hooked up).
 

sewlow

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How many miles?
The distributors in these trucks are bad for eating the drive gear.
The play that develops will mess with your timing.
It's a sacrificial part anyways.
The old SBC/BBC's had a replaceable bronze gear, but I believe that that bit of common sense has gone the way of the Dodo.
IIRC, a new distributor is the only fix for a bad gear on these trucks. Even still, easier to replace the distributor than the cam.
When mine needed replacing, I found that, at first, the pinging would only be apparent when under hard load. It became more so at lesser loads as time went by.
 

evilunclegrimace

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It is the distributor on the Vortec engines that have the problem with the drive gear, he has a TBI engine. Also the drive gear is replaceable on ALL of the SBC engines .
 

sewlow

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It is the distributor on the Vortec engines that have the problem with the drive gear, he has a TBI engine. Also the drive gear is replaceable on ALL of the SBC engines .
Ahh. Thanks.
Found this...
 

Schurkey

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As said, verify fuel pressure and initial timing. Assure that the timing advance works.

Connect a scan tool, verify ALL the sensors, especially the knock sensor. Common for the knock sensor wiring to degrade. If the O2 sensor isn't reporting correctly, the engine may be running lean.
 
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