Is this a rod knock, or what?

Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 15th 2017, 7:13pm

https://youtu.be/Wmi9SPcyR8Y
Van has been running great the past 6 months or so.
Was just at a stop light and the idle got really low and it sounded like she was about to die. I've replaced my vacuum lines 6 months ago and all the lines seem to be in good working order.
When I accelerate I hear a "knock" and the engine shakes. Once I'm moving I don't hear the knock but the idle is still really rough.
Checked my air filter hose thingy(that runs through the MAF sensor and everything is right.
Would a knock continue to knock the entire time my engine is running? The knock only occurs right when I accellerate.
But I definitely hear some noise like something came loose when I accellerate.
Going to try to post a video.

I'm trying to post a video but everytime I hit "add the file" it deletes what I type in here and I don't see any video attached.
Can you add videos to posts on this forum? Or is that like, too futuristic and stuff?
Last edited by Nubetoob87 on September 16th 2017, 6:33am, edited 1 time in total.
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Re: Is this a rod knock, or what?

Postby Rock-N-Blues » September 15th 2017, 7:55pm

I believe you need to upload your video to YouBoob, or similar, and then paste the link to it here! From your description it does not sound like a "rod knock" but could certainly lead to one, or worse if you don't fix the issue! From what you say, it seems that some sensor or your distributor went South, causing the ignition timing to go wonky! I would take it somewhere with a code reader.
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Re: Is this a rod knock, or what?

Postby AstroWill » September 15th 2017, 10:12pm

Nubetoob87 wrote:Or is that like, too futuristic and stuff?

Exactly!

BTW, for future reference, you can edit your post for 1440minutes(24hrs) instead of posting a new reply.

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Re: Is this a rod knock, or what?

Postby Big_kid » September 16th 2017, 2:05am

From the description, it sounds like it could be spark knock/piston slap. I once had a flexplate crack, it sounded like a lifter gone bad- but I had new lifters.
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Re: Is this a rod knock, or what?

Postby Coaster » September 16th 2017, 2:34am

classic exhaust leak. pass side. mine does this everyday
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Re: Is this a rod knock, or what?

Postby Astrofarian » September 16th 2017, 3:21am

Woodpecker.

You're welcome.

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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 16th 2017, 6:05am

Astrofarian wrote:Woodpecker.

You're welcome.

-M!ke-

What is that?
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Re: Is this a rod knock, or what?

Postby chevymaher » September 16th 2017, 9:40am

Nubetoob87 wrote:
Astrofarian wrote:Woodpecker.

You're welcome.

-M!ke-

What is that?


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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 16th 2017, 5:11pm

@chevymaher
Is that supposed to mean something or just you being "funny."
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Re: Is this a rod knock, or what?

Postby AstroWill » September 16th 2017, 5:56pm

In quotes and everything, lol

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Re: Is this a rod knock, or what?

Postby chevymaher » September 16th 2017, 6:56pm

Nubetoob87 wrote:@chevymaher
Is that supposed to mean something or just you being "funny."

That is what mike meant. It sounds like a serious predetonation in the video,
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Re: Is this a rod knock, or what?

Postby dchan51360 » September 16th 2017, 8:57pm

And it's not throwing a code?

Like Chevymaher says, sounds like predetonation.

Almost like the computer is unable to "retard" the timing enough to keep it from having a detonation problem. What was the full run of events that lead to this symptom. You said was running great but then said something about replacing all the vacuum lines.

What prompted you to change the vacuum lines? What is the history of the van before that? When was the van running fine at Idle?

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Re: Is this a rod knock, or what?

Postby Astrofarian » September 16th 2017, 11:22pm

chevymaher wrote:
Nubetoob87 wrote:
Astrofarian wrote:Woodpecker.

You're welcome.

-M!ke-

What is that?


Woody_Woodpecker.png


Sorry. You came here looking for an answer, not a smartass wisecrack. My bad

FWIW, does it do the same thing if you accelerate in reverse? I'm thinking pre-ignition as well but you MAY also want to check your motor mounts and exhaust gaskets/hangers/joints.
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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 17th 2017, 5:50am

dchan51360 wrote:And it's not throwing a code?
What was the full run of events that lead to this symptom.
What prompted you to change the vacuum lines? What is the history of the van before that?
When was the van running fine at Idle?DC


Went out and bought a decent code reader today. Got a P0300 misfire.
Changed the vacuum lines 8 months ago when I first got the van, because I wasn't getting proper control over my vents. The main vacuum hose was cracked and disintegrating. Also wasn't hooked up to the vacuum reservoir. But none of those hoses seemed to have anything to do with it causing a misfire(and I don't assume they ever would). So I replaced hoses, replaced check valvle and got control of vents.
Since I had the van it was always running rough, but not this bad. 8 months ago I finally checked codes, had a misfiring cylinder (due to cracked spark plug), and a code for a O2 sensor. I replaced all the spark plugs, plug wires, 02 sensor, distributor cap and rotor, pcv valve, and she was running like brand new. Also put in a new MAF sensor, and egr valve.. the van ran fine the past 8 months since these repairs.
I was just driving home the other day on the freeway, doing 70 like I normally do, when I exited the freeway everything was fine, couple miles later I was sitting at a stop light in Drive with my foot on the brake and it started shaking really bad and idle was fluctuating and sounded like it was about to stall.
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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 17th 2017, 5:56am

Astrofarian wrote:does it do the same thing if you accelerate in reverse? I'm thinking pre-ignition as well but you MAY also want to check your motor mounts and exhaust gaskets/hangers/joints.
-M!ke-

Yes, in reverse it makes the same noise.
It almost feels as if something came loose. I will check the motor mounts etc.
Thanks!
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Re: Is this a rod knock, or what?

Postby Rock-N-Blues » September 17th 2017, 6:42am

Well, the up side here, is that form your clear description of how the issue came about, it was likely just one thing that caused this. Seems like possibly a vacuum leak caused by one of the hoses you replaced falling off or cracking? The crap we have available at the local prats stores is not known for it's quality and/or longevity. Just wondering, did you replace the hose to the PCV valve? When I got my 91, the hose was broken right off and what was left was pretty deteriorated and crumbly. Replacing it cured a massive vacuum leak! :banana: I'm still suspecting a sensor, like maybe the knock sensor? Although not yet understanding how it works, what it does and how it functions, it's just a guess.

Logic tells us that this was probably caused by something that has the ability to fail instantaneously, as opposed to going South through gradual deterioration! Check all your vacuum connections, get back to us and let the experts here help you. Please also let us know what the eventual resolution ends up being.
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Re: Is this a rod knock, or what?

Postby Mmusicman » September 17th 2017, 12:44pm

Check for silly things (anything you've recently touched) ... maybe the distributor cap came lose, or something else
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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 18th 2017, 5:16pm

Rock-N-Blues wrote:Seems like possibly a vacuum leak caused by one of the hoses you replaced falling off or cracking?

I had my mobile mechanic come out last night to diagnose...
He checked all my vacuum lines and they're all good.
He checked the distributor, did a compression test (good) and a fuel pressure test (good).
He thinks it's the crank sensor.
So that is what I'm going to try to replace tomorrow.
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Re: Is this a rod knock, or what?

Postby Nubetoob87 [OP] » September 22nd 2017, 6:58pm

It was the distributor.
Threw a new one in and it's back to normal.
It's weird because I just replaced the distributor about 6 months ago.
There was some grease inside the distributor, under the rotor.
Wondering why the distributor would fail so quickly.
Maybe because it's a cheap autozone part... well, at least it came with a lifetime warranty so it was free.
I'll be spending the rest of my lifetime replacing these damn things every 6 months.
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Re: Is this a rod knock, or what?

Postby dchan51360 » September 23rd 2017, 2:37am

I suspect you had to return the bad unit but it would have been interesting to see the old one. I have seen a distributor top come loose (part that has the sensor is and where the rotor attaches to) one came partly loose so there was about 5 degrees of turning play. This would wreck havock on the timing.

I've also seen just the screws that hold the rotor come loose part way but not totally detach so that the rotor wobbles on the top. That I believe was from trying to reuse the old rotor screws instead of replacing them when you change to a new rotor (or dist) the new ones that come with a new rotor, usually have some "one use" thread locking gel that keeps them from vibrating loose. Reuse the old screws and they tend to slowly back out.
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