Strange misfire (P0302) on my new Scion

[SC Maintenance]

So to review - replaced the plug (twice), replaced the coil (twice). So your pretty much down to either an injector, or electrical (connector, ECU, etc). But I would think a bad ECU or connector would show up randomly, not just under load?

It could be low compression - but that is usually just as likely if not more likely to show up as a misfire under low load, in my experience at least - which granted is not vast.

 

[Elkins45]

So to review - replaced the plug (twice), replaced the coil (twice). So your pretty much down to either an injector, or electrical (connector, ECU, etc). But I would think a bad ECU or connector would show up randomly, not just under load?

It could be low compression - but that is usually just as likely if not more likely to show up as a misfire under low load, in my experience at least - which granted is not vast.

That pretty much sums it up. If it’s the connector or the ECU I’m still perplexed why the new coil automatically makes it much worse. With the old coil it seems to run fine at idle but if misses badly at every throttle position.

I have a compression tester that I’ve never used so I’ll probably give that a try eventually if needed. Right now I’m crossing my fingers that it’s a partially clogged injector because after running some cleaner thru it the hard miss hasn’t reoccurred.

 

[The Critic]

On my last test drive with a new plug in that cylinder I induced it by jamming the accelerator to the floor. It wasn’t as bad as during hill climbing, but you could definitely feel it and the CEL flashed but didn’t stay on.

I’m still completely perplexed as to why it’s always worse, and happens even at idle, with the new coil(s). There’s a part of me that wants to pull a coil off my 09 and swap it to see what it does, and to put the new coil in the 09 and see what it does, but I’m wary that it might break something that isn’t broken now.

Sounds like it misfires under load. I suspect a valve sealing issue. Check compression (hot and cold), and also perform a leakdown test.

You may also want to remove the valve cover to check for a broken valve spring. I chased a very intermittent misfire on a 2GR-FE that only occurred under heavy load and it turned out to be a broken valve spring.

 

[Elkins45]

Update: it’s definitely burning a lot of oil so it’s going to be getting a Berryman’s piston soak this week. I also pulled the valve cover to replace the gasket and this is what it looks like at 80k miles.

I guess all those years toddling around at 10mph really weren’t good for it.

 

[OVERKILL]

Update: it’s definitely burning a lot of oil so it’s going to be getting a Berryman’s piston soak this week. I also pulled the valve cover to replace the gasket and this is what it looks like at 80k miles.

View attachment 236885

I guess all those years toddling around at 10mph really weren’t good for it.

Wow, that's ugly! You could try the new Valvoline R&P, as I assume switching to HPL isn't a reasonable proposition for a $3K vehicle.

 

[Elkins45]

Wow, that's ugly! You could try the new Valvoline R&P, as I assume switching to HPL isn't a reasonable proposition for a $3K vehicle.

I have a can of BG 109 that I’m going to run through it after I finish the piston soak, but the Valvoline is a good idea for the refill.

 

[The Critic]

I have a can of BG 109 that I’m going to run through it after I finish the piston soak, but the Valvoline is a good idea for the refill.

Did you look at the valve springs yet?

 

[Elkins45]

Did you look at the valve springs yet?

I may be showing my ignorance but I don’t think they are visible because they are under the buckets. I sure didn’t see any springs.

 

[michaelluscher]

Not sludgy per se
But varnished worse than I would think for the mileage
Mine at 280k looked no better, but only a little worse

10k 0w20 OCIs weren't good to these engines

 

[Elkins45]

Not sludgy per se
But varnished worse than I would think for the mileage
Mine at 280k looked no better, but only a little worse

10k 0w20 OCIs weren't good to these engines

I was surprised by how dirty the VVT gear is. It looks like someone rubbed it with potting soil.