P0300 Misfire Diagnosis - help please

[jon55nj]

I have an 06 sport with 252,000 miles. A couple weeks ago I started getting some "hard starts" (shaking and not sounding right) when I first turn the key. When this happened the check engine light flashed. I turned the car off and turned it back on and there were no problems. About every 4th time I started it, the same thing happened. I have never had any problems while driving - only when starting. Within a few days of the first incident, the check engine light, VSC off and VSC trac went off and all seemed good for 4 days. Then two days ago this whole thing started again. Symptoms are the same - only rough when starting and if I turn it off and back on again... it has never happened in consecutive starts - and never any problems while driving - still runs great.

My friend has a code reader so we looked last night... P0300. I have read that the P0300 is fairly generic and could be many things so I am hoping that with this additional info somebody can help me narrow down the problem before I take it in.

About 4,000 miles ago I replaced the spark plugs with plugs from Toyota so I don't think it is that.

Thanks,
Jon

 

[fdbyrne]

Which engine do you have?

 

[jon55nj]

I have the v6

 

[jon55nj]

nobody? As an update - it went away with all lights cleared for another 2 days. It is now back so clearly it is an intermittent problem if that helps anybody with a diagnosis.

Thanks again.

 

[alia176]

Keep an eye on my thread "DTC code hell.....", as there might be some clues that could be helpful for you!

 

[YotaDriver]

I'm not familiar with the P0300 code, but any time I hear the word "misfire" in relation to the 1GR-FE I immediately think it's the head gasket.

The symptoms you've described also mirror those of the typical head gasket failure, i.e. rough idle at start, intermittent warning lights, etc. I've also got a 2006 with the V6 and I usually think we're more immune to this problem than the 03-05 vintage V6's because we've supposedly got a redesigned gasket in our engines, although there's some debate as to when during the 06 model year these new gaskets were introduced.

Anyway, one option you might have would be to have a leakdown test done. This will let you know definitively (I think) whether or not you're dealing with a potentially large repair.

Good luck man.

 

[jon55nj]

I thought I would follow up to this - Only thing I can think of is that I got some bad gas. Problem was still occurring and then I got new gas on an almost empty tank and I never had the problem again. It has been almost 6 weeks and not a single misfire or hard start. crossing fingers

 

[cruzmissile]

I had the same issue and code with mine. It would stumble pretty bad then go away.
I'd clear the check engine by removing the battery lead or clearing on the reader.
Turns out I narrowed down to a solenoid that advances the cam (looks like a solenoid with a plunger.
I replaced (part was $90) and its been clear ever since.
One big difference is that I have the v8.
I also got a secondary code for mis-firing on #1 cylinder which pointed me to the correct bank.

 

[alia176]

I had the same issue and code with mine. It would stumble pretty bad then go away.
I'd clear the check engine by removing the battery lead or clearing on the reader.
Turns out I narrowed down to a solenoid that advances the cam (looks like a solenoid with a plunger.
I replaced (part was $90) and its been clear ever since.
One big difference is that I have the v8.
I also got a secondary code for mis-firing on #1 cylinder which pointed me to the correct bank.

Did you get any other misfire codes? I'm curious if I should be looking at the cam adjusters on my GF's V8 and she is getting misfire from both sides.