At a loss - what to do at this point?

[jacksheadache]

Long story short - vehicle ran SOLID before the water pump failed, I had no options but to do it myself at the time. So I took it apart to replace the water pump and timing belt. This is a 2007 with the 4.7 with just under 250k on it.

Started it up, timing was apparently off by a tooth.

Took it apart, corrected that and made sure it was 100% spot on.

After reassembling everything the second time, I started the vehicle and noticed it was running better with no dash lights, smooth operation. I drove it for about 50 miles with no issues.

Later, while attempting to burp the system during a coolant swap, the dash lights came back on and the engine began running rough with noticeable misfiring.

Out of time and energy at this point so I decided to take it to a shop to see what they suggested

First Shop Diagnosis (Trusted Local Shop):

Code: P0302 – Cylinder 2 Misfire Detected

Steps Taken:

Swapped coil from cylinder 2 to cylinder 4 → Misfire stayed on cylinder 2.

Swapped spark plug on cylinder 2 → No change.

Compression test on cylinder 2 → 175 PSI.

Ohmed fuel injectors → 14.1 ohms.

Borescope inspection of valves and piston → No visible issues.

Observation: Misfire only starts after the engine has run for a few minutes, and it's isolated to cylinder 2.

Recommendation: Due to the unusual nature of the issue, they recommended taking the vehicle to the dealership.

Second Shop Diagnosis (Toyota-Certified Specialist):

Code: P0302 – Cylinder 2 Misfire

Steps Taken:

Swapped coils between cylinders 2 and 6 → Misfire remained on cylinder 2.

Swapped spark plugs between cylinders 2 and 4 → No change.

Compression test on cylinders 2, 4, and 6 → Cylinder 2 showed low compression.

Leak-down test on cylinder 2 → Pressure loss confirmed.

Conclusion: Mechanical issue causing misfire and engine noise.

Recommendation: Engine replacement due to the mechanical failure and high mileage (250k+ miles). They're asking 13k...




At this point I'm at a loss. The vehicle outside of what ever is going on is in solid shape. K02 tires in good shape, limited to no rust/damage, new water pump, timing belt, battery, alternator, front and rear brakes...

Do I get a third opinion and continue to dump more money into diagnosis?

Do I attempt to sell it as is? If so, I have no idea what it's worth as is.



Thank you

 

[Cezar]

Obviously one of the shops is full of crap but it's probably the one recommending an engine replacement

 

[jacksheadache]

Obviously one of the shops is full of crap but it's probably the one recommending an engine replacement

Right? I'm just not sure who to trust with it at this point.

I'd also like to avoid continuing to pay for diagnosis to be told "eh"

Was really hoping for option C, where it was something simple like a sensor or wiring causing something somewhere.. I like the vehicle and want to keep it if at all possible.

 

[Lemming]

Can you do a leakdown test on your own? I would want to confirm this loss of compression, if it were my engine.

Did it overheat?

 

[Hungryhawk]

Can the leakdown compression test separate valve to valve seat seal FROM piston ring seal to cylinder wall?
I would test cylinder #2 to confirm if valve issue or piston ring issue.
If a ring issue: Soaking cylinder #2 with Seafoam ( or similar) a few days then suction out. Flush combustion chamber with a light oil to remove Seafoam residuals. Then retest for compression test.
If a valve seal- you can evaluate a head removal and valve lapping repair.

I remember wet and dry compression tests providing piston ring seal information-but it has been decades since I did this type of assessments.

So no signs of head gasket leak allowing coolant into cylinder #2 ??

My 2 cents

 

[jacksheadache]

Can you do a leakdown test on your own? I would want to confirm this loss of compression, if it were my engine.

Did it overheat?

That's not a bad suggestion.

When the water pump failed I did drive it home. But I do so a few minutes at a time letting it cool down before moving for a few minutes again. The gauge was up but at no point did it overheat.

 

[jacksheadache]

Can the leakdown compression test separate valve to valve seat seal FROM piston ring seal to cylinder wall?
I would test cylinder #2 to confirm if valve issue or piston ring issue.
If a ring issue: Soaking cylinder #2 with Seafoam ( or similar) a few days then suction out. Flush combustion chamber with a light oil to remove Seafoam residuals. Then retest for compression test.
If a valve seal- you can evaluate a head removal and valve lapping repair.

I remember wet and dry compression tests providing piston ring seal information-but it has been decades since I did this type of assessments.

So no signs of head gasket leak allowing coolant into cylinder #2 ??

My 2 cents

Thank you. If I have it in me I may give this a shot.

I'm really confused with the timing of this. Being this wasn't an issue before the water pump failed.

 

[- Rita -]

I'm really confused with the timing of this

Timing correlates, though the outcome doesn't seem to.

A decent engine looks like ~5k, ~2k labor, ~1k misc ...how 13k?

 

[rideexileex]

Miles + Time + Heat = brittle wires... Does it seem like a complete cylinder shutdown or just occasional misfire? Could check to see if the injector is still getting a correct signal with a PWM multi-meter and/or replace(swap?) sparkplug wires.

 

[Drcoffee]

Check for spark on #2. Pull the plug, use a known good coil and ground the plug to the cyl head. This will rule out a broken/chewed wire. #2 isnt prone to HG failure like #6. Could also be a cracked spark plug. As it heats up it can fail. Might want to pull the fuel pump fuse first.

You said it happened while burping the coolant. Can you explain how you did it?

 

[jacksheadache]

Timing correlates, though the outcome doesn't seem to.

A decent engine looks like ~5k, ~2k labor, ~1k misc ...how 13k?

Yeah, that's a pretty good point. I think I was just off put by the diagnosis of "engine replacement" for the last recommendation that I didn't even question 13k. Assuming it's a brand new motor.. not really sure on that one but that's a big hard no haha.

 

[jacksheadache]

Miles + Time + Heat = brittle wires... Does it seem like a complete cylinder shutdown or just occasional misfire? Could check to see if the injector is still getting a correct signal with a PWM multi-meter and/or replace(swap?) sparkplug wires.

The misfire is pretty consistent but worse/more noticeable once it hits running temp. I think according to the shops that took a look they did swap plugs and coil around.

 

[jacksheadache]

Check for spark on #2. Pull the plug, use a known good coil and ground the plug to the cyl head. This will rule out a broken/chewed wire. #2 isnt prone to HG failure like #6. Could also be a cracked spark plug. As it heats up it can fail. Might want to pull the fuel pump fuse first.

Thanks for the advice. Maybe I'll do just that and at a minimum pull the plugs at some point and take a look.

 

[alia176]

The second shop did a real test using a leakdown tester. I'd go to harbor freight to buy this thing, bring it home, watch YT vids and do the test.

You need conclusive evidence before you hope for the best and throw parts at it. If the leakdown test shows something funky, the fix isn't that hard if you DIY it. Before going there, I'd figure out what's going on with that cylinder.

If the leadown test shows nothing funky, then you can move on to something else.s