LOUD rattle when engine starts

[OrgasmicLarry69]

Hello, I’ve came here as a last resort because I’ve tried everything

I originally planned on doing plug wires, spark plugs, and a cap and rotor as regular maintenance
All was well until I went to fire it up again.
And it makes a horribly loud rattle

It doesn’t do it when the starters engaged (I pulled the fuel pump relay and it didn’t do it the whole time, just when it was idling)

Afterwards I thought maybe I dropped something in the intake manifold, because the clearance was so tight I couldn’t get to the distributor.
Anyway, I took a magnet and a camera and looked inside to see if I dropped something and it had got stuck in the intake or in between intake valves. However everything was clean and no foreign objects were found.

Upon finding nothing concerning, I went back and put the new plenum gaskets back on and put the intake back together and hooked everything up, making sure nothing was done improperly (to my knowledge)

When I went for the startup the 2nd time around. It still made the noise.
That’s when a friend of mine told me to double check my connections and to make sure my plugs were tight and not leaking out of the spark plugs.
Everything was tight, and I even made sure all 8 plugs were receiving power from a spark plug tester.


I honestly don’t know where to go next.
I have a video of the noise and what not.
It sounds like it may be coming from the driver side of the intake manifold, closer to the EGR stuff
Or potentially the valve covers.
Idk why though.

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[OrgasmicLarry69]

Also, I should note a highly important piece of information
I accidentally when taking the intake manifold off the first time, there’s a thin long plastic hose that runs from the EGR to the canister
It has 2 hoses that go into the canister
From what I saw, the one beside it seemed fine, but the one that goes to the EGR had cracked and broken off

 

[Erin]

Also, I should note a highly important piece of information
I accidentally when taking the intake manifold off the first time, there’s a thin long plastic hose that runs from the EGR to the canister
It has 2 hoses that go into the canister
From what I saw, the one beside it seemed fine, but the one that goes to the EGR had cracked and broken off

My hose to the canister came off before. It didn’t cause a rattle, just a strong gas smell.

 

[Schurkey]

Exhaust tube from exhaust manifold to intake manifold (EGR) cracked/disconnected?

Good luck, they're extinct. Treasure-yard only, now.

I'll be VERY surprised if there's a "plastic" hose from the EGR to the charcoal canister.

 

[Erik the Awful]

I originally planned on doing plug wires, spark plugs, and a cap and rotor as regular maintenance

Is that all you did? Double check your firing order.

 

[OrgasmicLarry69]

Exhaust tube from exhaust manifold to intake manifold (EGR) cracked/disconnected?

Good luck, they're extinct. Treasure-yard only, now.

I'll be VERY surprised if there's a "plastic" hose from the EGR to the charcoal canister.

I meant EGR Solenoid
My bad

 

[someotherguy]

Is that all you did? Double check your firing order.

Very easy to get it wrong if you forget that the Vortec cap is not numbered exactly sequentially. You'd think it would be, but it ain't.

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Richard

 

[OrgasmicLarry69]

it’s been several days now
And with a couple buddies and myself
We’ve looked over everything

We’ve checked timing
We’ve checked the plugs and plug wires and made sure everything was getting spark
The cap and rotor itself
We double checked the firing order and made sure the plug wires from the distributor were going to it’s designated cylinder
We’ve made sure there was absolutely nothing stuck inside the valves from the intake manifold
We made sure all hoses and and harnesses were plugged in properly.
We checked EGR hoses, the EGR component, and the solenoid
We made sure something wasn’t in the way of anything in the engine bay
Like something hitting the fan or whatever crazy odds.

We even ran the truck for a few minutes while it rattled away to see whatever happened.
It didn’t blow up or sound bad.
It idles perfectly fine, it does it’s high idle for a cold start for a moment and idles down and maintains a steady rpm.
But it just rattles super loud with its speed depending on the rpm.

we checked all fluids and the oil was still fresh from when I changed it a few weeks ago
Still golden and no shavings or anything in the oil.

I even plugged in my scan tool and all that shows up is a crankshaft position sensor code
But I don’t see why it would cause the horrible loud rattle.
You can hear the rattle inside the house
Or a couple hundred feet away.

I just don’t want to keep blowing money trying to fix things that don’t fix the rattle.
Especially when the CPS costs 70 dollars alone and it may or may not fix the issue.

 

[Schurkey]

Exhaust tube from exhaust manifold to intake manifold (EGR) cracked/disconnected?

Did you ever check the EGR tube? All it would take is to bump it doing other work. I think the thing has an insulation shield over it, it could be cracked/broken inside the shield so that it wouldn't look broken.

Beyond that...try a cylinder balance test. Short-out the spark to each cylinder in turn, see if just one cylinder is making that noise or if it's all of them.

This is a TBI distributor, but you can do essentially the same thing with yours. The point being to NOT puncture the insulation, but to slide a blunted nail between the boot and the wire, so that the tip of the nail touches the metal end of the plug wire. Touch a grounded jumper wire or a grounded test-light to each nail in turn.

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What does the Crank sensor waveform look like?

 

[OrgasmicLarry69]

Did you ever check the EGR tube? All it would take is to bump it doing other work. I think the thing has an insulation shield over it, it could be cracked/broken inside the shield so that it wouldn't look broken.

Beyond that...try a cylinder balance test. Short-out the spark to each cylinder in turn, see if just one cylinder is making that noise or if it's all of them.

This is a TBI distributor, but you can do essentially the same thing with yours. The point being to NOT puncture the insulation, but to slide a blunted nail between the boot and the wire, so that the tip of the nail touches the metal end of the plug wire. Touch a grounded jumper wire or a grounded test-light to each nail in turn.

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What does the Crank sensor waveform look like?

I’d have to check the scan tool
Again tomorrow to see the graph.
It’s getting dark out now and my neighbors would probably throw a fit if I started the truck right now.
I wish I was exaggerating how loud the rattle noise is.
You can seriously hear it from a far distance.

I’ve had engines in the past with decent rod knocks that weren’t as loud as the noise being made in this big block.