What caused this engine fire?

[calrockx]

Here's what happened:

I left my place for my parents house, about a 45-minute drive. On the way, the Check Engine light came on. Okay, annoying, but things seemed to be running a-okay. Still, I was concerned and wanted to know something right away. I stopped at an auto shop a few minutes from my destination and it was a P0303 —*Cylinder 3 Misfire. I think I had one that a couple years back and it was a headgasket issue (which I had fixed, and that was after driving around with the light for few days with no further issues). Still, at this point, all seemed well. About a mile before I reached the house, I seemed to notice a bit of a weezing/air sound when I stepped on the gas, but I didn't think much of it, maybe I was just hearing things. I pulled into the garage, parked. Thirty to forty-five seconds later I got out, smelled something burning and noticed smoke coming from under hood. I looked under the 4Runner and saw flaming debris under the engine, maybe slightly toward the passenger side.

I got a bit of fire extinguisher on it, but then the smoke was pretty intense and I thought it best to get out of there. The fire department got there pretty quick and took care of the fire.

In hindsight, or next time, I'd probably stick through the smoke a bit longer and fight the fire, or maybe try to pop the hood from inside to give more room for the extinguisher. But hey, things could have been worse for a car fire.

Possibly relevant:
- I noticed in the last few days that when I'd start the truck, there was a sort of quick metal-scraping sound before the engine started. It'd start, but make that sound on the way. But this only happened on a low gas tank. Once filled up again, things seemed okay.
- The last bit of electrical work I had done was installing a new radio antenna, and that was a couple months ago.

So that's all I've got. I'll admit right here I'm not nearly as mechanically inclined as many of you, so I'm stumped. For what it's worth, I didn't notice the engine temp gauge on that last drive. I've overheated before, but it caught my eye then. So there's that.

And here are some pictures.

http://i.imgur.com/nla5JRf.jpg?1

http://i.imgur.com/mm5Jjya.jpg?1

http://i.imgur.com/GUNkbFw.jpg?1

http://i.imgur.com/8tJ70Xa.jpg?1

http://i.imgur.com/dMmX4UD.jpg?1

http://i.imgur.com/siZNgEm.jpg?1

[04 Rocko Taco]

This is a stumper, let me get home and compare your pics to what is actually still IN my engine bay... I realize the block and manifolds themselves are not really flammable and it would take a hell of a fire to melt them, so the fact that they are about the only thing still there doesn't help much... Like I said, going to have to go home and compare. I will just stick this placeholder here for now to place my theories later...

From the looks of the heat signature on the paint, etc I would say at first look, it sure looks like it was on the passenger side though.

[calrockx]

I wish I could offer some prize for the correct answer.

Also, the hood release warped so that the hood wouldn't open as usual from the front. The hinges were clipped and I held the hood up from the windshield side to get those shots.

[troyboy162]

I think I'm like fourth in line but decided against the rims. Good luck with the sales. Should be lots of goodies to help get some money back

[Robinhood4x4]

That sucks Charles.

What aftermarket electrical do you have under the hood? Any of those wires traveling along the passenger side?

So did the fire happen in the garage? Is the house ok?

[4x4mike]

Man that sucks to see.
Like Steve asked. What wiring was on the passenger side? I don't see a battery. Was it installed in the factory location?

[Seanz0rz]

From memory, the passenger side inner fender has, from firewall forward:

windshield wiper motor
main engine loom
starter
abs
cruise control
air intake (MAF)
and headlight/corner light.

On the engine you have the 3 coil packs, and quite a bit inboard of those, the fuel injectors.

I honestly don't think you will ever pin down a cause for the fire. With the misfire, that could have been a wiring issue in the main loom, causing #3 not to fire (but then #6 should have misfired as well...), could have been a short in the starter cable and it arced to the block until it caught something on fire (that decrease in voltage from arcing could have caused a misfire).

my guess is somewhere between #3 and the firewall. #1 coil pack looks in good shape, but the other 2 are pretty toast. Likely from the intake tube falling on them, but still. Could have even been something that fell on the exhaust. The AC lines are there, and that could explain the weazing sound you heard, and that should change with rpm with the ac clutch engaged.

That really sucks. I hope insurance treats you right!

[calrockx]

I definitely had some aftermarket wiring in there -- winch, bumper lights, underbody lights, CB, and the AndyMod -- but those were all on the driver side. Oh the ARB air locker compressor was on the passenger side, as well as (non-electrical) the snorkel and deckplate mod. Also, all those mods had been under the hood and working smoothly for years without any sign of trouble. The latest work was putting in a new radio antenna, but I don't see how that'd cause this, especially after a couple months of use (even if the antenna bent backward a couple times on the way down from hitting the low clearance when pulling in).

Also, only one battery, it was in the usual location.
http://i.imgur.com/SK2H9Nj.jpg?1

[calrockx]

And yeah this was in the garage. Thankfully it's no worse than some smoke damage in there. That's still a pain, but at least homeowners insurance is there to help.

[paddlenbike]

You said you had a code 303 on this drive, which is usually a bad coil pack. Did you stop and read the codes? Did you pop the hood at that time?

Chicken/egg...just trying to figure out if the code 303 came up because there was a fire, or if the 303 was related to causing the fire. The wheezing probably means you had a fire going, stopping allowed it to spread. Fuel leak?

[Seanz0rz]

Leaky #3 injector? certainly possible!

[calrockx]

This isn't exact, but a rough timeline:

12:30pm: leave my place
12:40pm: check engine light comes on
1:10pm: stop at Midas auto repair to diagnose check engine line. Park in a space, walk in ask for help. Pull up to front of garage, leave engine on, they pull code. I continue to my destination.
1:25pm: arrive at house, park, engine off.
1:26pm: doom.

[paddlenbike]

This isn't exact, but a rough timeline:

12:30pm: leave my place
12:40pm: check engine light comes on
1:10pm: stop at Midas auto repair to diagnose check engine line. Park in a space, walk in ask for help. Pull up to front of garage, leave engine on, they pull code. I continue to my destination.
1:25pm: arrive at house, park, engine off.
1:26pm: doom.

Sounds like the hood was never opened. I'm wondering if something was starting to smoulder at that time.

[calrockx]

Yeah, the hood wasn't opened. That's possible. I didn't notice or smell anything at least.

[paddlenbike]

On the way home from the Pismo Jamboree a friend's 4Runner got the P0303 misfire code. We popped the hood and could see the ignition arc'ing from the coil pack to the valve cover. (Replacing the coil pack fixed the problem.) Combine an arc'ing coil pack with a slight fuel leak and you have a problem. But back to the chicken/egg...something else getting hot could have burned up a coil pack and triggered the CEL.

[YotaFun]

Wow that so sucks, glad you didn't get hurt from it at least.

I am thinking that P0303 code was a cause of the impending doom.
The weezing sound could have been when what ever was igniting burning away at the intake tube, so every time you hit it, it was sucking extra air in.

As for the start of the fire who knows.
Leaking valve cover gasket onto exhaust.
Fuel leak from the rail end or from that number 3 injector.
A short in the harness itself, I have seen this happen on tacos but not cause a fire.
Power wire to compressor may have been rubbing on something and finally made it all the way through after all these years and started to arc.

That would be once expensive rebuild if you bought it back.
That brake master alone is worth $1500....

I can mail you a stock bumper I have if you can hold on to the other one for me till I figure out a way to get it to the east coast lol :-P

[calrockx]

When I stopped at that auto shop shortly before the fire, they actually pulled two codes. I forgot the second one but just called and asked the guy if he remembered it. It was a P0300...random misfire. So we can add that to the clues.

[paddlenbike]

I did a quick search and engine fires sure aren't common, but the 4th gen 4Runners were recalled for leaky fuel pulsation dampers.
ON CERTAIN SPORT UTILITY VEHICLES EQUIPPED WITH V6 ENGINES, THE FUEL PULSATION DAMPER, LOCATED ON THE FUEL RAIL, MAY HAVE BEEN IMPROPERLY ASSEMBLED, CAUSING A DIAPHRAGM IN THE PULSATION DAMPER TO BE DAMAGED. IF THE DIAPHRAGM FAILS, FUEL MAY LEAK.

Consequence:
THIS COULD RESULT IN AN ENGINE COMPARTMENT FIRE IF A HEAT SOURCE OR AN IGNITION SOURCE IS PRESENT.

3rd gens only had one recall, 2001s for lower ball joints.

[Seanz0rz]

2, the 96-early 98 for rear suspension bump stops in the coils.

[Robinhood4x4]

Also, all those mods had been under the hood and working smoothly for years without any sign of trouble.

The older the wiring the more likely vibration has caused chaffing of the insulation which would eventually lead to a short. As long as all the wiring was fused at the battery, there shouldn't have been a fire though.

Ken's note about the arcing sounds like a good cause.

[Bandit Runner]

Oh, so sorry to see this. Your rig was always an inspiration to me. Glad you are alright.