94 Caravan 3.8L - Timing or Rod Knock?

I think it's rod knock and the engine is toast, but neighbor suggested it
might be timing. So I went about trying to verify the mechanical timing was
correct.

My understanding is that there are sensors on both the flywheel and cam, but
not certain. Seems the computer would flag a problem. It's a chain, and
was recently changed by a completely incompetent mechanic, so ruling nothing
out at this point. I don't see how one can verify mechanical timing on this
vehicle w/o pulling the timing chain cover. Any diagnostic suggestions?

Ran fine for maybe 1000 miles on new chain.

Oil pressure occasionally drops out at idle. Did a cylinder take-down test
and heard no difference while any cylinder was disabled. I would have
expected to hear something if it was rod knock. Also, the knock gets louder
and worse when you rev the engine. Vacuum looks somewhat normal with no
obvious pulses. Besides the knocking that you can hear all up and down the
street, the engine sounds somewhat normal.

If you live in the Denver area and want this vehicle - tranny is new w/
warranty, AWD, new tires, newer paint, all new power steering, ~190k miles
....

- Nate

 

At 190,000 miles, it could be a rod knock. Also, high mileage 3.3's
had a problem where one of the rocker arm mounting towers would crack,
and create a noise that could sound like what you describe. I don't
know if the 3.8 had it too, and if / when it was resolved. You can
check allpar.com in the 3.3 engine section for more info.

Also, I don't think that this engine has any external timing marks so
you can verify that the valve timing is correct. The crank and cam
senors control the ignition timing like you say.

-KM