lower engine knock

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lower engine knock

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lower engine knock - 9/19/2005 4:29:26 PM

Talusgirl

Posts: 334
Joined: 9/18/2005
Status: offline

My first priority is to fix the digital dash connections. I don't know how long I can go w/out getting a speeding ticket by just guessing how fast I'm going. Plus it's a pain when you don't know how much gas you actually have in your tank. So thanks guys for the advice! We'll work on it today.
The major problem, aside from the rust, (which I'm working on) is the engine. It has a loud knock which seems to be coming from the lower part of the engine. I took it in and one mechanic told me I need to replace the engine! Said it would probably cost around $1500 (20 hrs. labor) Didn't expect that! But I got the impression that he didn't know exactly what it was until he could take it apart. He said it wasn't a valve thing though.
I've heard 2 other Blazers (at the bank, gas station) that sound just like mine. Is this a common thing? Can it be rebuilt? Problem is, he couldn't explain exactly what the problem is. It's a clunking loud knock. Sometimes it pauses for a second before acceleration. Always startes right away, but a big cloud of smoke is emitted from the tail pipe. A few times it's started rough. It has a 4.3 Vortec V6 engine. Otherwise it drives great, smooth, good acceleration (sporadically does the pause thing). The idle is fine-not like it wants to die, but it sounds almost like a diesel engine and the knocking is quite loud. I love the truck (it's a '91) and wonder if it's worth putting a ton of money into. Can I just drive it like this, until the engine finally dies? It's got about 127,000 miles on it. I'm stuck-any advice?

Post #: 1

RE: lower engine knock - 9/20/2005 9:07:09 PM

zero psi

Site Moderator
Posts: 1075
Joined: 8/22/2004
From: maynard, MA
Status: offline

it really could be a lot of things. its hard to tell with out being there listing to it with a stethascope to pinpoint the noise. you got the truck cheap enough so i say do the motor swap cause whetever it is making the noise, it cant be good. drive it till it dies, then swap in a motor.

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(in reply to Talusgirl)

Post #: 2

RE: lower engine knock - 9/20/2005 9:13:53 PM

Talusgirl

Posts: 334
Joined: 9/18/2005
Status: offline

Thanks for the response. I'm getting a lot of feedback on the 'swap' question. Just some details that I need-like what needs to go w/the engine. Seems like a huge undertaking w/labor. But the 2000 engine has so few miles on it and I know my sister babied it.

(in reply to zero psi)

Post #: 3

RE: lower engine knock - 9/21/2005 10:40:07 AM

Hanr3

Wheels & Tire Moderator
Posts: 3482
Joined: 5/11/2005
Status: offline

I agree, a loud knock could be anything. I have a '93 with 190,000 miles on it. It also makes a loud knock. Although I suspect a crank bearing in my case, or a broken connecting rod. Previous owner found metal shavings in his oil. Only way to tell for sure is to pull the oil pan. I gave him $50 for it and towed it home. I have a 4.3L engine from a fullsixe that I am going to drop in until I get this one rebuilt.

Anyway, I left you my thoughts on your delima. Sorry about not replying sooner. Spent last couple of nights under the '87 replacing the muffler and leaky tranny cooler line. What a pain in the tush.

Just had a thought, are you sure you don't have an exhaust leak at the exhaust manifold where it connects to the block, or where it connects to the y-pipe?????? Its a long shot, but I have heard stranger noise discriptions in the past leading me to think one thing when it was something else completely.

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(in reply to Talusgirl)

Post #: 4

RE: lower engine knock - 9/23/2005 8:43:03 PM

Talusgirl

Posts: 334
Joined: 9/18/2005
Status: offline

Go on www.pistonslap.com -that is what my engine sounds like (make sure your speakers are on-doh)

(in reply to Hanr3)

Post #: 5

RE: lower engine knock - 4/28/2008 10:38:02 AM

BLAZERBOY_08

Posts: 1
Joined: 4/28/2008
Status: offline

To all with an ENGINE KNOCK.
I have a 1993 Chevy Blazer Full Size 4X4. The engine knocks... I was able to trace the knock down to one of my pistons, by pulling each spark plug wire (one at a time) if the knock goes away you know you have a problem with that piston.. well in my case that was not entirely true. I dropped my exhaust and pulled my oil pan off and check the con-rod bearing for that piston, and it was perfectly fine. So i proceeded to check all of them since i was down there, they all looked very good! So now what? Well I just got off the phone with a real gear head and he told me that it is more than likely my rear main bearing. So today i will be pulling that bearing cap and with a little plasti-gage i will be doing some measuring. If this is the problem i will be letting all of you know..

-keep on truckin

Aaron Morlatt

(in reply to Talusgirl)

Post #: 6

RE: lower engine knock - 4/28/2008 6:34:31 PM

swartlkk

Posts: 14499
Joined: 5/1/2005
From: Waterloo, NY
Status: offline

WOW... Old thread???

On a knock, it could be the rod bearings, main bearings, wrist pin, or piston slap

< Message edited by swartlkk -- 4/28/2008 6:42:19 PM >

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