Replaced the cylinder heads on my 04 Toyota Sienna 3.3 and now getting misfire codes for 1, 3, and 5. Shouldn’t there be a cam correlation code if the timing belt is off by a tooth? It starts fine but runs rough as it warms up, and I’m hearing a pre-ignition knock under load. Any advice?
If the timing is off by more than a tooth, yeah, you’d typically get an error code for that. Have you checked the timing marks yet?
Blaine said:
If the timing is off by more than a tooth, yeah, you’d typically get an error code for that. Have you checked the timing marks yet?
Not yet, but that’s next on my list. I noticed the VVT solenoid isn’t engaging when the scanner commands it. Any idea when the ECM tells it to activate?
@Axelle
The ECU doesn’t use a fixed point for VVT. It looks at stuff like engine speed, throttle position, and coolant temp before deciding. Might wanna check for oil blockages too.
@Axelle
Wait, what’s VVT? I’ve heard it mentioned but never really knew what it does.
TimothyPerez said:
@Axelle
Wait, what’s VVT? I’ve heard it mentioned but never really knew what it does.
Variable Valve Timing. It adjusts how your engine’s valves open and close to improve performance or efficiency depending on driving conditions.
Misfires on 1, 3, and 5 could mean an issue with the front head. Are you sure the alignment marks were correct when you installed the cams?
Leander said:
Misfires on 1, 3, and 5 could mean an issue with the front head. Are you sure the alignment marks were correct when you installed the cams?
Yep, made sure to align the single dots on the LH head and the double dots on the RH head. Pretty confident there.
@Axelle
Good to know. You might still want to double-check the oil passage for blockages—it could stop the VVT from engaging properly.
Are 1, 3, and 5 on the front head? Just checking—I always mix up the cylinder layout on these.
Wei said:
Are 1, 3, and 5 on the front head? Just checking—I always mix up the cylinder layout on these.
Nope, cylinders 1, 3, and 5 are at the firewall side. Bank 1 is back there, too.
@Axelle
Ahh gotcha. Thanks for clearing that up. Makes troubleshooting a little easier when I know what’s where!
Pre-ignition knock sounds scary. Are you sure it’s not something more serious like a bad sensor or the wrong timing setup?
Macon said:
Pre-ignition knock sounds scary. Are you sure it’s not something more serious like a bad sensor or the wrong timing setup?
Could be, but it only happens under load and after warming up. I’m hoping it’s just a timing issue.
@Axelle
Let us know what you find when you check the timing marks. Fingers crossed it’s a simple fix!
Not engaging VVT could explain the rough idle. Did you check the oil pressure in the passage to the left head?
Page said:
Not engaging VVT could explain the rough idle. Did you check the oil pressure in the passage to the left head?
Not yet, but I’ll definitely add that to my list. Thanks for the tip.
@Axelle
No worries. Sometimes it’s the little things like that which get overlooked.