P0306 Engine Code - Hard Shake for 30 seconds that clears up - Help Needed

Gents (and ladies),
You all helped me out greatly on my last post (http://www.tacomaworld.com/forum/2nd-gen-tacomas/272254-05-tacoma-p0306-need-your-help-2.html). However, I'm at a stand still with my 2005 Tacoma and my P0306 - Cylinder 6 missfire. In short, I need your help again.

Here's where I'm at (feel free to read the old post, but I'll give you the 10 second tour to get you up to speed):

The Symptoms:

1. I get a P0306 code on my 2005 Toyota Tacoma v6 SR5 - Cylinder 6 misfire
2. The truck shakes fairly hard for the first few seconds after starting, but smooths out after about 1/2 minute and runs fine.
3. It only started doing this after I cleaned out the throttle body, and sprayed mass airflow sensor cleaner on the MAF.
4. I also recently flushed my coolant, but it was acting up prior to the flush as I recall - I could be wrong on that, but I'm fairly certain it was.

Here's what I've tried/had done:

1. I replaced all 6 spark plugs (gapped them as well) - runs a tad better, but did not fix the problem
2. I've tried swapping coil packs on cylinder 6 - no change
3. I had my coolant tested to see if exhaust was getting into it - no leaks, no problems
4. I had my engine pressure tested - no leaks, all checks out

So, I'm kind of at a loss on what to do next... Thoughts?

Thanks in advance for any advice!

 

okay, lets use the process of elimination...

swapped coils, still misfire on #6
went to the trouble of having it checked with leakdown test, came back clean...
new plugs, still have the misfire, but not as bad...

New plug probably throwing out a little better spark, so it isn't as bad, but still there...

This sounds like an intermittent fuel delivery problem on the #6 cylinder...

So, the injector could be going, or, the ecu is having some problems...

My Taco will do the same thing on occasion after a heavy rain and sitting over night, the miss goes away after 30 seconds to a minute, sometimes shutting off the engine right away and restarting solves the problem....

I replaced the plugs and it got better, but every once and awhile it does it little misfire sequence...once all 6 are running right, no problems...

I do not have the park and miss problem the OP describes, I am fairly certain a new injector will solve the problem...

You could test this theory by swapping #6 injector with another and see if the misfire moves with the injector...

Just some thoughts..

Good luck...

 

A few possibilities:

-Injector #6 as above
-Vacuum leak at #6 intake manifold gasket or immediate area.
-The leakdown/pressure test was done when the engine was a still bit warm, and it passed because it was warm. I'd follow the advice from the other thread, and pull #6 spark plug after the truck sits overnight, check for raw coolant on the plug, then have someone crank the engine briefly to check for mist. Keep in mind if it is coolant entering cylinder #6, its a very minute amount at a time.

 

I would double check the connection in coil pack #6, I mean the contacts inside could have corrosion or something. Clean them real good and apply some of that dielectric grease on the connector to keep moisture out and keep good continuity or maybe the wire inside is broke. good luck man

 

Alright, I appreciate the input folks! Sounds like there's a few things to try at this point:
1. Fuel injector swap - This is a great idea, not sure why I hadn't thought of it at this point.
2. Pressure test on a cold engine - Another great idea. The dealership should warranty their check, so I may tell them to let it sit over night, then do it. Great idea.

As far as the connection in coil pack 6, I actually did check it out, and put on dielectric grease (this was my initial hope ).

I'll keep everyone posted on how things work out.

Thanks again!

 

I hate to say it but it sounds like a bad head gasket.Cyl#6 is known for this. The best way to be positive is put the cooling system for about 30 minutes.Remove spark plug from cyl#6 for the next step you will need a borescope after removing spark plug look in cyl#6 and you will see a small trickle of coolant.The fact that you say it shakes for a few seconds at start up makes me almost positive that it's your head gasket.The reason you get a miss at start up is that cylinder has to get rid of the coolant in said cylinder.I have seen this a few times in the past year.Good luck I hope for your wallets sake that I'm wrong.

 

Yes, this was discussed in his original thread he linked to in the first post. To be honest, my gut feeling is the same, but my hope for his sake is also the same.

 

Do a cylinder leak down test after the engine has been sitting over night, and when performing the test remove radiator cap and look for the coolant to bubble. Last two 4.0 I did that was the only way I was able to see that it was leaking after disassembly found head gasket no good also new gaskets are of a different design.

 

head gasket! sorry dude

 

Ya'll are making me nervous... But it's ok. I've already been tipped off to this in my last post. Which is exactly why I had the stealership do the pressure test. I just didn't think of having it tested when it's cool. At least for the time being, I've got some things I can test. Stay tuned. I promise to keep everyone updated.

 

Alright... So, I know this is crazy, but the issue went away. Really... it did. The weather remained essentially the same (still cold in the morning, warmer in the evening), and it simply decided one day it was done shaking.

Really.

Now, I know it's likely to crop up again (unless of course it was an injector that appears to have cleared itself). When it does/if it does, I'll be sure to update everyone.

Otherwise, I'm going to take an ignorance is bliss approach until I see it come back :/.

 

Mine's doing the same thing. Just bought it last month too. And I did actually notice a puff of white smoke out the exhaust when I got the rough start one time. Major suckage. I can do a head gasket but it's certainly not my idea of fun. Had to change one on my BMW in May.

 

FWIW...my '05 4.0 just started throwing the p0306 right at the 150k mark (I ride moto's most of the year, NICE)....rumbling upon cold start up for 20 seconds then it's fine. TWF research quickly pointed out failed head gasket. Checked my coolant reservoir and it was almost down to low mark so I topped it up...that is a big indicator as I found no coolant leaks. I changed my plugs using DENSO, gap verified, and cleaned the MAF and throttle body while everything was apart. Plugs were really bad...almost 50k I'm embarrased to admit. Had to really take my time pulling each plug because of that, even though I used copper anti-seize on my last change. Little loosy, little tighty, repeat, repeat, repeat until they all came out without incident. Truck ran better and MPG went up quite a bit but still had the shudder at cold start. I was about to call my mechanic to pressure check the cylinder and exhaust gas in coolant when I ran into a friend who told me about a product called 'K-Seal' that worked for him with similar problem. I got the 8 fl oz bottle for $14, shake, pour into coolant reservoir, top up reservoir again and drive. This was 6 days ago and my truck has not had a shudder since. Coolant stays topped up. Like OP, I know I'll likely need to do the head gasket in the future but for now it's the best $14 I've ever spent. Don't know how it works to seal the leak...but I sure am grateful to Solv-Tec for making it. And NO, I am not a paid spokesperson, just a dude that needs to not spend $2k right now on a head gasket. Now I need to buy another bottle in case it comes back.

 

Be sure to check the coolant level of the actual radiator and not just the reservoir.

 

Thanks TnShooter ... yes, I've been doing that. Radiator itself has stayed topped up and is nice and pink...so little room the small bottle of K-Seal had to go into the reservoir. Just the reservoir kept going down. Checked again today and it is still right on full, no P0306 and no studder at startup. I hope this fix lasts me at least a couple years...we'll see. Cat's are frightfully expensive.

 

Hopefully it seals it up for a good long time.
BTW, you could have sucked some fluid out of the radiator to add the sealer.
But it sounds like got it taken care of.

 

These are common symptoms of a headgasket.

Easy way that I quickly tell is to run the engine with a coolant funnel. Once its bled, rev up. Little bubbles? Combustion.