‘97 5.7 automatic backfire go BOOM!

[97SWBCHEVY]

Anyone wanna diagnose what has happened? Lol
It hasn’t had any recent work done…been running fine…good oil pressure, no overheating problems… 178k… does have an ole Powerdyne Supercharger…
Just cruising about 45 mph going through town, kinda felt a lil miss briefly then abruptly lost power as and the loudest 2 backfires I’ve ever heard!
l pulled it off on a side ride…did some quick check under the hood…nothing jumped out at me…attempted to fire it back up once and backfire is all I got…
I’m hoping it’s a distributor issue but I know that is the best I can hope for…

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[Schurkey]

Distributor problems are very common. Defective caps, loose caps due to broken distributor housings, defective gears so the distributor goes out-of-time with the camshaft.

Connect a timing light, verify initial timing. Or spin the crank damper to TDC, see if the rotor lines up with the distributor cap terminal for #1 or #6.

Connect a scan tool, look at the cam sensor/crank sensor synchronization (sometimes called "Cam offset" or something similar.)

What is your fuel pressure?

How old are the spark plugs, plug wires, cap, rotor, fuel filter, etc?

 

[97SWBCHEVY]

Distributor problems are very common. Defective caps, loose caps due to broken distributor housings, defective gears so the distributor goes out-of-time with the camshaft.

Connect a timing light, verify initial timing. Or spin the crank damper to TDC, see if the rotor lines up with the distributor cap terminal for #1 or #6.

Connect a scan tool, look at the cam sensor/crank sensor synchronization (sometimes called "Cam offset" or something similar.)

What is your fuel pressure?

How old are the spark plugs, plug wires, cap, rotor, fuel filter, etc?

Ok while I don’t have a clue how what happened happened I do know what happened! Lol
When I took the distributor cap off I found that the 2 screws holding rotary button/cap in place had some how vibrated or backed out and it and the 2 lil screws were just bouncing around under the distributor cap! The guy I bought it from had recently had new plugs, wires, button, & cap etc work done before I bought it from him. I’ve had the truck for over a year but it’s not my daily driver and it stays parked for the most part…but I’ve atleast put 200-300 miles on it running around town…
I went ahead and bought a new distributor complete w cap etc…and put it in last night…problem now is my gf’s 5 year old was playing getting in and out of my truck etc…and while I had the old distributor out and was take a drink of my beer he tried to crank it…so me marking the old distributors position and just going back in with the new one and being done went out the window…I got #1 up etc and got it all back together and she cranks up and runs…but I’ll be honest I’ve never dealt much with setting the timing or anything on vehicles w ecm’s, cam sensors, crank sensors…and or a scan tool…so this question may be a stupid one…but is it possible for me to be off by like one tooth on the cam gear/clocking and the truck still crank, idle, run fairly smooth or would it not crank at all??? I know it’s not 100% right and I’m gonna have to get a scan tool on it, but there isn’t much room to turn the distributor to adjust the timing like old school days!

 

[Schurkey]

When I took the distributor cap off I found that the 2 screws holding rotary button/cap in place had some how vibrated or backed out and it and the 2 lil screws were just bouncing around under the distributor cap!

Rotary button/cap? You mean the "distributor rotor"?

Yup, that'll do it. The screws might not have been properly tightened, or the piece they screw into may be damaged.

I went ahead and bought a new distributor complete w cap etc…and put it in last night…problem now is my gf’s 5 year old was playing getting in and out of my truck etc…and while I had the old distributor out and was take a drink of my beer he tried to crank it…

This is why they invented "spanking". What if your arm had been on the radiator fan or the fan belt, or you had the fuel system disconnected? He turns the key, slices your arm, pinches your fingers between belt and pulley, or fuel sprays all over, and maybe gets ignited and burns the truck down. If the truck is in an attached garage, he burns the truck and the house down.

so me marking the old distributors position and just going back in with the new one and being done went out the window…I got #1 up etc and got it all back together and she cranks up and runs…but I’ll be honest I’ve never dealt much with setting the timing or anything on vehicles w ecm’s, cam sensors, crank sensors…and or a scan tool…so this question may be a stupid one…but is it possible for me to be off by like one tooth on the cam gear/clocking and the truck still crank, idle, run fairly smooth or would it not crank at all??? I know it’s not 100% right and I’m gonna have to get a scan tool on it, but there isn’t much room to turn the distributor to adjust the timing like old school days!

The timing on a Vortec 5.7L is not adjustable. You can turn the distributor, but you're NOT changing the timing.

Turning the distributor does two things: It synchronizes the cam sensor signal from the distributor, to the crank sensor signal. This allows the computer to know which cylinder is misfiring (if there's a misfire.) It also aligns the rotor tip to the correct terminal on the distributor cap, leading to lowest spark voltage required. If the distributor housing were turned too far, the spark could jump to the wrong distributor cap terminal, leading to misfire or a non-running engine; and possibly engine damage.

Yeah, you're gonna need a scan tool to check "Cam sensor offset" or whatever your tool calls it. If it's far enough out of spec, it'll set a code. If so, you'll want to clear that code, too.

 

[GoToGuy]

Ever see the utube of the guy just brought home new red shelby mustang. Everbody ooh, ahh, shiny! Kid in drivers seat turns key or push start button. ( Yeah Baby!) Lights off with first cylinder through the garage door into the garage keeps going till nose buried in far wall two feet in wall.....of house! If your doing maintenance, any no matter how minor or major. The vehicle and area around vehicle, be it land, sea or air is similar to a Nuclear Waste Zone. Stay Back. Stay Away. Don't Touch My Tools. And nobody gets hurt. The screaming and bleeding so irritating.

 

[Hipster]

The screaming and bleeding so irritating.

LOL!

 

[HotWheelsBurban]

LOL!

And why it's not a good idea to leave the keys in any vehicle when kids are around.... especially if said kids' parental units haven't explained to them that the car/truck being worked on is not their playroom.
Back in the early 80s when I was in high school, I learned one of my friends, when he was little, had been playing in a van that his grandpa was under, working on it. He accidentally put the van in gear, it came off the stands, and killed his grandpa. Now it was a tragic accident that didn't have to happen, and he was little enough that he really didn't know not to get in the van, but he is carrying that guilt for the rest of his life.

 

[smdk2500]

Also another reason pretty much every repair manual printed says to unhook the negative battery cable.

 

[97SWBCHEVY]

Rotary button/cap? You mean the "distributor rotor"?

Yup, that'll do it. The screws might not have been properly tightened, or the piece they screw into may be damaged.


This is why they invented "spanking". What if your arm had been on the radiator fan or the fan belt, or you had the fuel system disconnected? He turns the key, slices your arm, pinches your fingers between belt and pulley, or fuel sprays all over, and maybe gets ignited and burns the truck down. If the truck is in an attached garage, he burns the truck and the house down.


The timing on a Vortec 5.7L is not adjustable. You can turn the distributor, but you're NOT changing the timing.

Turning the distributor does two things: It synchronizes the cam sensor signal from the distributor, to the crank sensor signal. This allows the computer to know which cylinder is misfiring (if there's a misfire.) It also aligns the rotor tip to the correct terminal on the distributor cap, leading to lowest spark voltage required. If the distributor housing were turned too far, the spark could jump to the wrong distributor cap terminal, leading to misfire or a non-running engine; and possibly engine damage.

Yeah, you're gonna need a scan tool to check "Cam sensor offset" or whatever your tool calls it. If it's far enough out of spec, it'll set a code. If so, you'll want to clear that code, too.

Well I can’t really put it on the kiddo it was my screwup as much, if not more than his…but we did have a talk about it…

it’s back together and fires right off but it’s not right…it’s pinging and knocking and making all kinds of racket…lol
So it’s parked until I can get it to a shop or get me a scan tool…just not sure if that’s gonna fix whats broke…

 

[97SWBCHEVY]

Also another reason pretty much every repair manual printed says to unhook the negative battery cable.

Yes Sir…