Interpreting leak down test results

Newbie mechanic here, trying to save my Prius. 2010, 190k miles. Engine began knocking and throwing P0302 misfire code. Noticed that the coolant is a bit low (but I haven't ever really topped it off.) I cleaned the intake and replaced the PCV valve. Problem continued.

Now I bought a leak down tester to confirm if this is a blown head gasket - but I need help interpreting the results.

First I pulled the spark plugs out, and the spark plug from Cylinder #2 (the one misfiring) was black and oily.

Then, I ran a leakdown test on each cylinder. #1 and #2 were good, but #3 and #4 both leaked around 60%. I listened carefully, and really it seemed like the leaking sound was coming from the same cylinder which was being tested at the time. Nothing from the dipstick hole, no bubbles in the coolant. Am I doing this right? I removed, reattached, and reran the test several times to make sure it had a good seal. I also tried turning the engine down 360 degrees to get back to TDC again just in case I was on the wrong stroke.

I suppose cylinder #3 and #4 are leaking into each other? (even though the sound seemed to be coming from the cylinder being tested rather than the adjacent cylinder?)

Any thoughts on what this all means? Does it still sound like a blown head gasket or could it be something else? Thanks

 

I'm really confused, because cylinder #2 held pressure from the leak down test fine, yet I'm still getting misfires in Cylinder #2.

I tried rotating the spark plugs and coils, and drove it around a bit today. Rattled a lot upon starting the engine, but then smoothed out and seemed to run just fine, but still threw the P0302 check engine light.

I'll keep an eye on the coolant level, but I'm not sure how much I should be driving this thing. What else could be causing the misfires in cylinder #2 considering that it holds pressure fine but the spark plug was a bit wet and oily?

 

Now this morning I started the car again and it had a subtle knocking when the engine was getting going but smoothed over after about 10 seconds.

However it threw P0300 and P0304 random cylinder and cylinder #4 misfires

Anything else I should try or should I just get rid of this car?

 

I've never really done any mechanical repairs to cars before, so taking apart the engine feels beyond my abilities. At that point I think I would just sell the car to somebody who wants to do that.

My goal is to simply confirm if the head gasket is indeed the problem, so I'm not unloading the car for cheap unnecessarily.

 

I put the coil from #2 into #3. And I think I had previously once gotten a misfire in #4 even before swapping. I'm also still getting misfires in #2.

 

Yes when this misfire problem started, my first stab at it was to was to clean the intake manifold, pipe, and replace the PCR valve. It was crusted up but didn't appear blocked. Cleaning it didn't help.

(Sorry for the confusing multiple threads - I had thought it might be organizationally helpful to ask new questions in new threads)

 

Just an update for the records:

Brought the car into the shop for a second opinion. They pressurized the cooling system and found no leaks. Ran a compression test and found fairly even compression between the cylinders. Then they replaced the spark plugs with new ones and didn't get any knocking so they called it a day and sent the car home with me.

The next day I almost immediately got the check engine light with P302 and P304 again (misfires in cylinder 2 & 4) and also started getting new codes: P0352 & P0354 (Ignition coil circuit malfunction in B & D)

I brought it back to the shop, and they suggested either replacing the coils, or just ignoring the problem since the engine knocking has stopped. I suppose I'll just do the latter unless I feel any engine skips, and if I do I'll try replacing the coils. Maybe run some fuel injector cleaner through the tank and hope for the best.

 

Hmm... I'm starting to notice a really strong kinda sweet smell after starting the engine. Also sometimes a cloud of smoke.

Surprisingly no new misfire code yet but I can hear the stutter.

I think you guys have been right all along and this is really sounding like a busted head gasket. Time to let go I suppose...