Well folks....it has been a LOOOONG time since I have been on these forums. My 4runner is now at 140k miles. Was running great, until the dreaded "stutter at start-up" gremlin reared its ugly head. It would only happen after the car sat for an extended amount of time (usually overnight). It would turn on, engine would run rough until I "goosed" the gas, then it would be ok. If I drove it to work, shut it off, and tried restarting it after only an hour or 2, it would be fine.

Today I got a check engine light, as well as the VSC lights were lit up (which seems to happen whenever the CEL comes on). Used my scanner that I bought from Costco ($30!!!!) and it showed that there were 2 codes. P0305 "Misfire on Cylinder 5) and P0305 (pd) which I guess was a pending code for the other code(?). Was planning on taking it into the my guy to look at it, but instead went to go buy a coil pack for that particular cylinder and new plugs for all the cylinders. I will do the work tomorrow when my wife gets home so she can watch the 3yo. I will also clean the MAF sensor, and check the PCV valve. Any other thoughts? Does this sound like a bad fuel cap issue?

EDIT:Looked in the Haynes manual at the other trouble codes. If it was the coil pack, would it also throw trouble code P0355 "Ignition Coil 5 primary/secondary circuit" or does that mean something else? What code would mean for a bad gas cap?

It won't be a fuel cap issue, the code would be more of a P0455 or something.

Do you get a bit of white smoke when you start-up the vehicle and/or it stutters? When you change the plugs see if any look like they've been washed or have coolant on them.

I hate to say it, but it sounds very symptomatic of some of the headgasket failures the forum members and I have been seeing on pre-'05 4th gens.

x2...

Yeah......that is what I am afraid of with the HG issue. It must have heard that I was looking to trade her for the '16 Tacoma when it comes out. What color am I looking for on the sparkplug that would show coolant getting to them? I have not noticed any white smoke from the exhaust, other than the initial bit when I start up the engine and it is cold outside.

Time to replace the ole head gasket... don't bother troubleshooting, when you replace the head gasket everything will go back to normal... and the big picture is, it's a blessing in disguise because you never really want to buy the first couple years of any model redesign if at all possible. (your current failure case an point...)

Well here is an update. I unhooked the battery and removed the spark plugs and this is what I saw (Cylinder #5 plug on the right). The thick grease looking substance on the threads is anti-seize. I checked in the cylinder (it was all the way up, so I could see clearly in--lucky me!) and saw no coolant. I haven't noticed a decrease in the coolant level or white smoke from the exhaust, so as of right now there is no signs of a head gasket leak. I replaced the coil for cylinder #5, and once all the spark plugs were changed I started the truck up. The plugs only had 20k miles on them, but I figured I would change them all out while I was doing the work. Smooth as silk! All of the rough idle is gone!

I ran my OBD scanner, and the P0305 (pd) code wasnt showing anymore, which to me would mean that it was indeed the coil since that is a "pending" code. If I replaced the coil and the "pending code" wasnt pending anymore, then I am assuming that was the cause. I cleared the P0305 code with my scanner and the CEL went off. However, my ABS and VSC TRAC light were flashing, after the VSC OFF light went out. Did some research, and found out that the OBD scanner must be using the wrong protocol, so I had to do the Zero Point Calibration using 2 paper clips. Once I did that, drove the truck and I now have no issues. I will see how it holds up over the next week or 2. But it looks like it is fixed.

Glad it worked out so far. The V6s use Copper plugs that are recommended to be changed out every 30k. Those don't look like they've been contaminated with coolant, so that might be a blessing. I would keep tabs on it if it comes back, but glad it worked out!

Also, yes the '03-'04 do tend to reset the ZPC when you clear DTCs, even with a factory scantool; just a weird quirk of that model year.

Thanks Blackworks. The plugs I pulled and the plugs I put in new where Denso PKH20TT Platinum TT Spark Plugs. I did notice that I still did have the slightest of a stutter at startup, which **very quickly** fixes itself. I just put in some Lucas Top End Lube which I had heard good things about when it came to cleaning fuel injectors and valves. That might be unclogging the injectors as that is what I thought it could have been to begin with. I originally thought it was a sticking injector, which "unstuck" after I did the quick rev-up trick. The true test will come tomorrow morning when I start it up to go to work. It was always the worst when it sat for 8+ hours. When I pulled the plugs I didnt see anything that would suggest a coolant leak either.

Wish me luck!

Good Luck.

Here's an article that you should likely read...
AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - Symptoms of a Blown Head Gasket

There are a lot of different kind of head gasket failures which make it really hard to diagnosis. The difficulty of diagnosis causes a lot of us to live in denial and treat the symptoms instead of the root cause.

I'd bet your head gasket is starting to or has already failed in some form or fashion.

I can't remember ever hearing of spark plugs or an ignition coil actually causing a misfire in a 4th Gen 4Runner. If your only sympton is a misfire in #6 right now, my guess is the head gasket between #6 and #4 has a very minor leak.. when the engine is warm, the gasket swells to seal it back up. You may be able to extend the life of the gasket by using a high mileage motor oil that is suppose to swell the engine seals and gaskets... but eventually you will need a new head gasket, just like I will on my 2005.

Thanks for the information. One thing is that yesterday it ran so rough I couldnt even move it, and the error codes were thrown. I shut off the car, changed the plugs and coil, and did nothing else. Started it up and the codes were gone (after reset) and it purred like a kitten. That is why I would guess that I got the problem corrected. It was also just happening at the very first start up of the day, which to me would signify that something was "sticking" when allowed to sit for a while, which is why I was thinking fuel injector. If I ran it, turned it off, then restarted in the near future, it would be fine. Obviously I will keep an eye on the situation, and will update as necessary.

It started up this morning with no issues. Can still feel the slightest of roughness, which since i keep a very close eye on my truck, was not present about a month ago. I did notice it after i filled up with gas on the Jersey turnpike about a month ago. I actually made a comment to wife while driving that i thought i got bad gas or something. Just weird how it seemed to correlate. Seems like the Lucas product is working, because the now miles i drive the better the engine feels.

maybe that gas station has water in it's tanks... ethanol in fuel exasterbates the water collection issue, so I would say drive it until as empty as possible and then take it for some ethanol free fuel with some techron. It's the most logical cause outside of the headgasket from everything you've shared. Again, good luck.

I have refilled it twice since that fill up. I have noticed a roughness every since, so i wonder if i picked up some crud in the gas. Like i said though, it seems like it is getting better since putting on the Lucas Top end lube. I think at this point it is coming down to a fuel delivery issue....ie. injectors.

Trade now !!!!!

Not going to trade until that new Tacoma comes out.