Gen 2 used motor problems

Try a leak down tester. Read this article and see what you think.

Compression Testing vs Leak-Down Testing | Pegasus Auto Racing Supplies

 

It is well known that old gen 2 engines tend to burn oil, often substantially. Therefore, it probably will not be possible to find a good engine from junk yards in the U.S.. Perhaps you can source a very low mileage engine from Japan.

 

Um, burning oil has nothing what-so-ever to do with compression. Compression is compression, period.

 

A leak down test is the ONLY way to determine the condition of a non-running engine w/o a tear-down. Very likely BOTH engines are "good", you just cannot spin them fast enough to do a quality test. Most "compression tests" are done at cranking speed with a battery charger connected and the throttle plate WIDE OPEN. All are things which are impossible on a Prius. A leak-down test bypasses all of that and applies regulated air to the cylinder @ TDC (and often also @ BDC), measuring how much leaks out.

 

That’s not true. If your compression ring is worn your going to have a worn oil ring and you will blow by lots of
Oil.

 

Not necessarily. Most engines lose compression from overheating or ingesting dirt, neither of those typically affect the oil control rings as they are very low tension to begin with. Most oil consumption is from valve guides, poor quality oils can cause the oil rings to stick as another common malady, or a PVC system that is allowing too much air thru the system, which carries oil with it.

You can have great compression with massive oil use and the converse as well. My point was, although not clearly made, just because you have low compression does not mean you automatically have high oil consumption.

 

Am I the only one who is wondering how John is doing a compression test if the engine is not installed and therefore is not spinning at 300 RPM at minimum.

 

Patrick, see my post, which is #5 above.

You are spot-on tho, 200 RPM is considered the minimum to get a valid test.

 

I think you will find the problem is small bit of carbon getting caught between the valve and seat. When you remove the spark plug you disturb small bit of carbon and they are causing the problem.
I've been a motor mechanic for 45 yrs and I got caught by the same thing. Told the customer the compression was poor, removed the spark plug again to demonstrate to problem to the customer and there was full compression there this time. Rather red faced I asked around the trade if they had even had that and this was the answer. If it has been a long time since the engine has been run or the plugs have been out, you need to loosen the spark plug, then retighten them, start the engine and let it run for a while, then do the compression test.
You could try compressed air into the spark plug hole while spinning the motor over and see it that will clear the carbon out of the valve seats.

T1 Terry

 

89 in.-lb or 7.4 ft.-lb.
80 in.-lb for the bolts that hold the spark igniters to the valve cover.

You are supposed to use FIPG on the two places where the front cover, engine head and valve cover meet up.

What is the odometer reading on the replacement engine?

 

Congratulations!

 

Doubtful, very much so.

If a cat MELTS, it can block or restrict the exhaust flow, the photo you posted does not suggest any melting or other restriction. The sole job of the cat is to reduce emissions thru the process of "catalytic reduction", chemically altering/recombining combustion byproducts into less harmful ones. It is a chemical, not a mechanical process.

The *most* likely cause of p0420 after engine work is an exhaust leak, followed closely by resetting of the adaptive strategies in the ECM.