same code on 05 4 runner 4.0
replaced all spark plugs,
same result
replaced the coil on 6,
same result,
replaced the fuel injector on 6,
same result,
I wish I had read this forum before I started throwing money at the shop! Why don't they read up on what they are doing?????>

I guess it will be the head gasket from here, but how long before I have to replace the head gasket on the other side???

The quotes that I've seen are only slightly more for doing both than just one. Go ahead and take care of both now.

First post - really amazing website by the way.

Googled "2004 Toyota forerunner running rough" and drilled down to this post.

I believe I have a blown HG. I have 230K miles, bought it with 7 miles on it September 2004.

Some months ago the CEL light and traction (VSC?) lights came on. Manual says it is most likely caused by PCV issues due to the gas cap not sealing tight. My gas cap may be faulty by the way. The light would come and go, and finally came on permanently.

Local Goodyear folks were able to clear the codes during oil change and I moved on.

At some point I got rough idle at start, after a warm up it would stop.

At some point I noticed overheating, discovered that the vehicle had lost coolant. I replenished and didn't really think to ask why I had lost coolant. Hence the screen name.

Anyway, I discovered that I required regular refills to the radiator to maintain engine temp in normal range. I further discovered I was leaking water - I could see it dripping from the engine onto the ground, near the inside of the passenger front tire. My neighbor says "looks like your water pump is leaking". Makes sense to me, right? I decide to keep filling the radiator at regular intervals as a temporary solution.

Just recently the car would stutter when accelerating while in gear. It didn't replicate while in Park or Neutral. This didn't replicate during very slow acceleration, as long as RPM's we less than 2K.

Just two days ago it was running very rough at start and almost had a constant stutter.

After reading this entire thread, with my very limited knowledge of combustion mechanics, I believe that I do not have a water pump leak, I believe that the water leak is from a blown HG and the water is forced out there. I partly say this as I purchased some white label Blue Devil (after reading this post) and followed the instructions this morning. After cool down, I started it up while I had some initial stuttering, it appears to have stopped temporarily.

It is too much of a coincidence that the issue abated after using the HG sealant correct?

I think there are other issues as well. I am embarrassed to say I don't know if I ever changed the spark plugs. Other basic maintenance issues sucha s oil change and air filter change, brakes I've done.

Any comments, advice, criticism? What should I do next? What other maintenance steps might I take, other than the obvious HG repair, that I see will start at $2.5K?

Great site guys, by the way. I wish I had this kind of mechanical initiative.

Is the check engine light currently on? If so, take it to a local auto parts store and have them pull the code. They will usually pull the codes for free.

If it's a head gasket problem that' been occurring for as long as you say, then it's surely firing error codes that will point you in the right direction.

It does sound like the head gasket to me, however.

Yes the CEL is still on.

I'll take your advice and have the codes pulled.

What is the long-term prognosis if it is indeed a HG rupture?

You'll need to get it fixed sooner rather than later. I just had mine done. It cost me $2500 and from what I gather, that's on the low side. My heads checked out find and weren't warped because it never overheated. if your heads are warped it may cost more.

The good news is that once it's fixed, it's fixed for quite a while. You shouldn't have to worry about it again.

I just did the head gasket replacement on my 05 4runner with 240k miles on it. I did the job in my garage .Took a total of around 20 hrs. Removed the engine from the 4runnner and did it on a stand. Took the heads to machine shop and had a valve job done on it $450. Parts and machining together were around $1200 with new pump and timing chain kit. Easy straight forward job with some exp of other engine removal and installs.

Let it sit overnight. Remove the suspected cylinder spark plug. Use a borescope to look down in the cylinder for any signs of coolant. This is the best way I know off too confirm coolant leaking into a cylinder after it's been sitting.

i have a 2004 with slightly less miles, same thing going on just replaced the plugs definitely made the car feel better but still idles very rough upon start up. Had a compression test and is definitely not the HG... Did you ever find a solution to yours,,, let me know if you did , I am in Charlotte also do would like to know who you use for toyotas

I would still be willing to bet it is the HG, even with the compression test passing.

Me too, unfortunately. A leakdown test would be more conclusive.

If its a V6 with #6 misfire and mostly happens when it sits for a while then its the head gasket. Seen plenty and done a few, Spark plus i doubt it i've seen these with 260k on stock plugs and it still runs perfect which is crazy for a 30k plug.. Im a Toyota Master tech if it matters.

Testing compression wont matter it will read good, dont bother wasting your time, these engines are pretty much bullet proof besides the odd head gasket issues or the front covers leaking.. I own a V8 so i didnt have to deal with it if it happened

So leak down vs compression test. Is there a difference and if so which would be better for determining a HG failure?

Do a leakdown test. That would be the best for diag headgasket

I have a 2000 4runner completely stock and today after going over a huge bump she cut out and rolled to a stop. I started her up again and she was misfiring and wouldn't go over 1500 rpm before cutting off. Barely limped it home. I'm used to working on older cars so i was thinkin' i could've thrown the timing off, i don't see a distributor so it's one of those electronic ignition deals... anyways could i have screwed up a few of the coils? or bashed a spark plug into disrepair? did I blow out the injectors? or maybe even conked out the sending unit/ fuel pump? has anyone else had this problem? PLEASE HELP!!!