P0300 Pending. Driving advice?

[C6H12O6]

Quick advice before I have time to search through the history of 'MUD. Hopped in the 100 to go to work today and the UltraGauge beeped with a notice of a pending P0300 code as I pulled out of the driveway. I parked it and took the 40 to work, but I'm curious about next steps before throwing money at it. 2007 with ~150K miles. Been running great with no real issues other than a gas cap code when it was really hot last week, and excessive battery drain with the fridge running lately.

Should I drive it a couple more drive cycles to see if the pending code actually turns into a P030X specific cylinder misfire to help diagnose it, or just avoid driving it at all and try to figure it out from the P0300 code and the many, many things it could be? My initial search seems to suggest a bad coil, or maybe injectors, but it's been running fine with no hint of either, including the brief run this morning. The only weird thing I'm thinking of now that I type this has been two times after a dead battery in the last couple weeks that the first start after the battery charge, the truck didn't start with the normal turn of the key. Started up fine both times on the second attempt, and ran a tiny bit rough for maybe 5-10 seconds, but then it was fine.

Thanks in advance. I'll search more later, I promise.

 

[OEMGUY0720]

You are correct, this is a misfire related code (could be a spark plug or ignition coil or both). Best is to inspect them one by one and label them accordingly. Inspect for any cracks in ignition coil and heavy carbon deposit (burnt tip) on the spark plug -this could be your culprit. Check if the spark plugs are properly torqued as well.

 

[C6H12O6]

Will do, when I have time. I replaced the plugs and checked things with the timing belt service at 90K, but that was 60K miles ago, so I suppose plugs could need another look. Seems early, but you never know. Best practice is to replace the plugs anyway if I'm inspecting them and changing coils out, I would guess. I'll probably replace allthe coils if one or two are cracked, as i've heard they tend to start failing in pretty short order after the first one.

 

[Hugh Heifer]

Sounds like you felt the misfire of a coil going bad. Been there. I had to drive mine off a mountain with a bad coil once - that hurt my tummy. Now I carry 3.
You could get one new one and trouble shoot by moving it through the cylinders. Or replace them all - at 150k if they have not been done they are coming due.
Have you reset the code to see what it did next? It may not duplicate.
Sounds like you need a new battery though - and a gas cap.

 

[C6H12O6]

Haven't reset the code. I headed straight to work and didn't drive it again until this morning when I moved it into the driveway to work on it. Pulled the pending codes from the UltraGauge and now have P0300, P0301, and P0302. They might have all been there yesterday, but I was in a hurry.

Pulled the coils and plugs on #1 and #2. Plug #1 was loose, but thankfully not falling out and no apparent damage to the threads in the head, so that's great news. Plug #1 is on the left. Pretty easy to see it was about to get much worse. That coil and plug both had reddish-brown fouling. Oddly, both plug and coil #2 looked fine. Plug #2 was tight and the coil and plug show no signs of heat damage, but I'll probably replace all the coils and plugs as PM at a bit over 150K.

 

[C6H12O6]

Gas cap for sure is on the list. Battery is less than a year old. Not sure what's up there. Brought a good multimeter home from work that will read mA better than my 30-year-old Sunpro multimeter, so I'll dig into that later.

 

[C6H12O6]

All eight plugs and coils are out. Right side (PS) all seemed ok. Plugs tight, coils look fine. L-R, cylinders 2-4-6-8. A little oxidization on the ceramic around the electrode, but they all looked about right for 60K miles and all gapped right about 1.0-1.1 mm. You can also see the anti-seize crud on the top of the plug threads. Will be skipping that on the new set and torquing to 18 lb. ft., as per the info on Spark Plugs Alert Alert Alert!

Driver's side was less good, but still not catastrophic. L-R, cylinders 7-5-3-1. Cylinder 3 also had a loose plug and the coil looks equally heat-affected as #1. Weird that the codes were for cylinders 1 and 2 and that 2 looks great and plug was tight. We'll see. The rest of the DS coils had some degree of browning of the tips, whereas the PS coils all looked grey and fresh. Ordered new plugs and coils from Amazon ($48 each!), so we'll just roll the dice they're all legit Denso parts. Camping trip planned for Labor Day weekend, so time was a bit of the essence. I'll keep coils from 4, 6, and 8 for spares.

 

[C6H12O6]

Just to wrap this up (I hope), got the plugs torqued down on Saturday and the coils went in today. Everything fired up nicely and was smoother and quieter than the engine has seemed in a while. Drove it around town running some errands this afternoon and no pending codes remain.

UltraGauge for the win. Glad I caught this early and avoided any real damage.

 

[OEMGUY0720]

Very nice, glad things worked out.