'04 2.4 throwing codes p0300 - 0304

We put a new head on my dad's '04 2.4 Tacoma with around 200k on it. It starts up and seems to run OK at higher revs and when he drove it around the block, but it idles very rough and eventually cuts out. As said in the title it threw codes P0300 301 302 303 and 304. from what I gather 300 is a multi cylinder misfire, and the rest are misfires for the individual cylinders.

Does anyone have any experience with these particular issues? Could this be caused by having the timing slightly off? or simply a wire connection that may have been overlooked?

for what it's worth, at some point when we were taking the head off the knock sensor wire got pulled out of the connector, to fix this we spliced a new connector on the wire. Could this potentially cause misfires without throwing a knock sensor code?

Thanks in advance for any input.

 

Check your vacuum lines for leaks

 

Yes - it's conceivable the wire splicing screwed up the ability of the ECM to read the (voltage-based) knock sensor signal correctly (in terms of line voltage or waveform).

It's also conceivable that the knock sensor itself is messed up somehow from having the wire jerked out of it, and the ECM is getting a 'bad' reading.

You'd get a code (e.g., P0325) if the knock sensor signal was totally 'dead'. It appears your ECM is getting a knock sensor signal, but the ECM may be having trouble 'making sense of it'.

The ECM retards timing in response to a knock indication from the sensor, so a screwy sensor reading could easily result in timing (and hence misfire) issues.


NOTE: I'm not saying this is the only possible cause. But since you mentioned the sensor wiring issue it seems to me that's the logical place to start.

 

from my experiences on this it's more than likely you timing chain is not on correctly. Had this happen on a Civic and it threw all sorts of 300 codes and I tried everything until I took the cover off and noticed I had somehow jumped 2 teeth. Also while replacing the timing belt on a 2000 Avalon.

 

IIRC, after drivign it to work for a few days and reseting the trouble code a few times, the symptons gradually went away. it stopped throwing codes and he got it smogged.

My guess is that the wire we spliced had to settle in or something.

I think the only problem he had now is an unrelated exhaust rattle.