Any help/advice would be appreciated. I'm trying to know whats wrong with my 05 4Runner. Here are the symptoms and what has happened recently:

Codes: P0304 (Cylinder 4 Misfire) AND C1201 (Engine Control System Malfunction)

About 2 weeks ago there was a rough idle at start up, then a day or two later the P0304 code popped up. I hadn't changed the spark plugs for the past 35K so I figured I'd start there. Gapped them properly and replaced all 6 spark plugs. The plugs looked a little worn, but not terrible and I didn't notice any coolant. I also wasn't looking for coolant so I might have not noticed it, but it wasn't glaring. The only think I noticed was a slight discoloration on the coil pack for cylinder 6. A little brown, but barely noticeable.

So, I drove the car and for the next 3-4 days it was better, but occasionally would have a rough idle on cold start. Then on day 3 or 4 the code came back. This time it was both P0304 and C1201. So I replaced the coil pack on cylinder 4, took off the positive terminal on the battery and the codes were gone.

Similar symptoms - occasional rough idle on cold start, and the codes came back on day 2.

So today I took it to a local shop. Their diagnosis - "probably a blown head gasket - $3500 estimate." It failed a chemical test. The mechanics notes says it failed a pressure test but when I spoke with him on the phone earlier in the day, he didn't mention this. Not sure why? He was gone when I picked up the vehicle.

So here is why I am wondering what is going on: There are no other symptoms. The heater works, it has plenty of power, gas mileage is normal, thermostat is always on the low end of "normal", there is no white smoke coming out of the tail pipe, there is no loss of coolant, there are no bubbles in the coolant reservoir.

I do notice the smell of fuel in the coolant reservoir tank. Also, the rear windshield wiper and auto up/dn window stopped working at the same time of these problems.

Any thoughts? I will call the mechanic again tomorrow to get a bit more information, but any advice would be great. I can take it to Toyota on Thursday and will likely do so.

Also, if it is the head gasket, what would you do? It's an 05 with 175K on it. It's in fair shape cosmetically - hit a deer in December and fixed the cracked bumper cover myself along with replacing fog lamp housing. I cannot do this job myself. I don't have the tools, the time, or the know-how.

05, V6 SR5 4x4

If it failed the Chemical test then you've definitely got a HG problem. It takes quite a bit of exhaust gasses to get the color change to happen. I'd shop around and see you can get someone to do it for under 3 grand. As far as what Id do....

Id keep the truck if it's paid off. While yes this $3k is a lot to spend on a 14 year old truck, its also only equal to like 3-4 months car payment on a new car. I notice your in WI so if the 4runner is otherwise nice and doesn't have rust issues, just fix it and drive it.
You'd be at least spending probably 8-9 if you were to buy a similar rig, so yes while its expensive, its usually cheaper to keep the car you have

If you need to buy some time, saving up for the repair, you can probably get away with driving it as long as it doesn't misfire when its warm...

Yea, mine at 160k leaked. Super mild symptoms, but in the end, it likely will need replacing. I usually chime in to try a quick fix additive to see if it can hold off more leaks, but some would advise against that.
Good luck!

Had to replace the head gasket on my 05 a couple years ago at 190K Km's. Leak seemed to be very slow but eventually resulted in loss of coolant and white smoke. Hard decision to make but glad chose to commit to it and did it. Still issue's appearing that need to be fixed but really nothing major, CV's, exhaust leak, little creaks and rattles, wheel bearing soon it sounds like and eventually suspension which I'm kind of looking forward to doing. Still happy to have it around. If you like the vehicle then do the work is my suggestion, just keep in mind you will have ongoing repairs. Also, going to be hard to unload a vehicle with a blown hg.

Man what a bummer! I’m in the same situation as you. Blown head gasket. The wife and I just got our 00 T4r about a week ago and then we find out this! Best of luck man!

Sounds like a common problem with the 4th. Gens. I have thought about installing an electrical fan just to keep it extra cool on hot days.

It seems very common on the 03 to early 05 V6 engines. Then the timing chain stretch issues popped up in 07. I'm wondering if the OP ever figured out what to do with his.

Actually, very uncommon on 03's, heavy in 04 and 05. If you were to go through the failure thread, you'd find very, very few 03's which makes no sense unless they changed something in 04 that created the problem. I counted up all the responses at one time and reported the statistics here and asked why but no one had an answer.

That's interesting. I guess I lumped 03-04 together in my head because they should have the same gaskets.

Just keep in mind that the Poll was only on this forum so there's many more 03s out there that aren't on theses forums, I'm willing to bet there are less 03s on here then there are 04s and early 05s.

I'm just going by the assumption that most want to get the newest 4th Gen that they can find and or afford and as such there's less 03s on here.

I am sorry to hear that, I have been dealing with a multi cylinder misfire that only happens after the vehicle is warmed up and driving down the road, and that you had a lot of trouble narrowing down. My 06 developed a mis about a month ago that is intermittent at first and now is more prevalent. I have changed plugs, coils, fuel pump, injectors, MAF, checked for vacuum leaks, ran every test my snap on scanner is capable of, and ohms checked and voltage checked the wiring harness and sensors. The only things I have not replaced yet because I am waiting on parts to come in is the fuel pressure regulator and the fuel pressure pulsation damper. After I replace those, if it isn't fixed I will be at a loss. I have searched TSB's and forum after forum until my eyes hurt and brain hurts. I am very mechanically inclined (schooling & years of working on vehicles including some fabrication). If this doesn't work, I may end up taking to the dealership and throwing my hands up until they can come up with something. There is no loss of antifreeze or oil and neither is mixing or being burnt in the engine.

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I figured mine out, it turns out somehow my spark plug gap ended up between .065-075. after readjusting the gap to .040 and finding out that I pinched the rubber fuel line to the new external fuel filter when I installed the fuel tank skid plate. I made these changes a few weeks ago and so far so good.