At the shop I work at we had a 94 gmc 1500 with the TBI 4.3l engine come in with the complaint that a rat built a nest on top of the engine and now it misfires badly. Customer had it towed in to us. I looked under the hood andseveral vacuum lines were chewed up as well as a couple plug wires. Vehicle would crank but not start. Further inspection once in the shop I found that the coil terminal on the distributor was loose and nearly falling off. Tell the customer we can start with a tune up and go from there. I replaced plugs, wires, cap, rotor, pcv, and all damaged vacuum lines. I also noticed the throttle body gasket was leaking so I replaced that too while in there. The old plugs were black and coated in gunk. After everything was back together I fired it up. It wouldn't get up to idle speed and sounded bogged down. Let it run for a minute then shut it down to do a diagnostic and a cam position sensor on another car. Talked to a coworker who has the same engine in his truck and got him to listen to it while I started it. Almost as soon as I started cranking he spotted flames in the tb so I stopped cranking. He was waving out the flames and I was starting to get out of the truck when boom! I saw a fireball come out of the passenger side of the engine bay and our sales guy felt the shockwave all the way in the office. My coworker up front was fine but the explosion came out the right bank's rocker cover, literally splitting it in half and blowing the larger half out of the engine bay.



I'm really at a loss here as I've never in my life seen something like this happen. Any advice or ideas would be appreciated.

lol that happend to a coworker in my shop but he was using brake cleaner to clean the engine bay out and look for an air leak. he didnt know a spark plug wire was arching. one little spark and the whole **** house went up n i could feel the procution about 50 feet from him. whats funny about it was i was on the phone with a mazda tech line guy at the time and he even asked me what was the noise.

lol

Attachment 16452



This is what's left of the rocker cover from the right bank. Here's our theory. Customer cranked and cranked till it flooded and hydralicked causing the timing chain to jump a tooth or two. By the time I pull it in all the fuel hadrun down into the oil pan. I do the work and try to start it. The timing being off allows the plugs to fire with the intake valve still open causing fire in the intake manifold. Fire ignites fumes coming up from pcv and crankcase vent and kaboom. Catastrophic explosion of gasoline vapor fumes in the crankcase

Yikes, that's nuts! So do you have to buy the guy a new motor?

Super glue!

No, it was a serious condition in the engine that caused it and we weren't informed about it so not our fault lol. I still need to check the cam/crank timing but I keep getting pulled off it to do brake jobs. Did notice the other day that the rockers are so loose I can nearly rotate them off the valve springs lol

a sure case of valvecoverus expoldicadus!



while you're probably close on the diagnosis, its also possible the rats/mice/bin laden hid something in there.

Yeah, I did notice he had a brand new air filter so it's possible the critter had chewed through the old one and left presents on top of the tb or in the intake. If that was the case he still didn't tell us that lol

Another thing that makes me curious is that a chevy parts guy informed me there wasn't a vortec engine in that truck that year.