u/Aeyix

Started having misfire issues on my 2.4L 2007 RAV4 (2AZ-FE) again. To give a quick history, cylinder head cracked in 2018 rebuilt by Toyota. Then cylinder head cracked in 2024 and I rebuilt it with aftermarket parts. Started having misfiring issues last year and diagnostic testing on my own lead to nothing and issues primarily time me from codes it was cylinder 1 but all cylinders would eventually throw a code shop said timing was off but no code and math came out to 1 tooth. Checked and tonight looked good. Measured valve clearances and found no clearance on one of my exhaust valves, swapped out a lifter and fixed the issue. Still has rare misfires but not enough to cause codes or issues driving.

Well recently started having misfire issues again where I have to warm up my car again. No coolant burning or dumping like the previous head cracks. Visual inspection of all components look good, smoke test of intake good, fuel pressure good. Compression is 30psi low on cylinder 1 compared to the others. Leak down comes out to 30% on cylinder 1 and sounds like its coming from cylinder 2. Put a hose on cylinder 2 and can feel the air coming from. Only 7% leak down though on cylinder 2. My friend says he can fairly feel the air coming from 1 but I can't. 3 and 4 only have 2% leakage. Mainly getting misfires on 1 and sometimes 2 but codes on all eventually. No other codes.

I'm going to be opening it up and preparing for what I'm suspecting is a bad head gasket that is somehow letting air one way and replacing my after market fel-pro with an OEM Toyota this time. I'm also considering replacing my aftermarket head with a junk yard head just due to the issues I've had since and doing full timing job to be safe based on the pressure transducer test the shop did under a year ago even though I was lined up on my timing marks.

But why would leakage go one way and not the other, is the head gasket the likely culprit?

As title says. I did a simple home test strip test to confirm what I kind of already knew. I've gone ham on getting all sorts of filtration setup for our home because frankly, I believe it's what led to the death of our second child before his expected due date and all of his abnormalities. Though we can't confirm, I'm not taking a risk again and we were about 10-12 weeks pregnant with our first by the time we moved in and we've had no filtration beyond the refrigerator filter and water softener.

Our main neighbor is a farm and we knew prior to closing that Nitrates were disclosed from the well test but nothing else.

I'm looking at Tap Score and their Advanced Well Water test is $400 on their website covering 114 different tests while buying their Advanced Home Water test through Amazon seems to cover all the main things I'm looking for without doing a full table to table comparison covering 116 tests for only $270. So significantly cheaper. Or I can go for what I was originally looking to pay at $400 for their Ultimate Home Test which is over 250 different tests. I'm not sure of anything on there will be of any benefit additionally over what the previous two tests cover.

Misfires and testing leads to 30% leakage cylinder 1 into 2 but not nearly a much the other way around?