What caused this engine fire?

[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.