Red78rooster

1995 G20 Van

Kind of continuing a situation from a previous thread about the cluster panel. I had every intentions on changing out my water pump when my engine developed a small knock. It would only do it when it was in reverse or drive and not park or neutral. As I took it to my mechanic to check out, He said that I did not have a water pump issue that it sounded more like a spark knock. Being that the Van is 30 years old I was unsure when the last tune up was done. As I begin to remove plugs wires I noticed that it had been a very long time since a




tune up had been done. I installed new spark plugs, Wires, distributor cap, and rotor button. That made a big difference on the vehicle, But I still have a slight knock. I don't think it is as bad now as it was, But it is definitely something that needs attention. Any help would be much appreciated.

mountainmanjoe

well if it only happens in certain gears then it's more likely to be drivetrain related.

Is this at idle, or rolling down the road?

Red78rooster

Sometimes as soon as I take off, sometimes I get a couple miles down the road.

mountainmanjoe

OK I would inspect the driveshaft U-joints. If it hasn't been lubed in years it could be binding or already worn out. Same with axle pinion.
Bad motor/tranny mounts can also get noisy.

Red78rooster

Going to try the knock sensor that is located behind the starter.

mountainmanjoe

So you think the engine is pinging? Try some premium fuel

William Kisselstein

Typically a loose driveshaft u-joint will make itself most known when you let off the gas at speed. Under load there's pressure on it so it doesn't vibrate.