intermittent knocking sound at idle

[rmoltis]

So my 96 aspire has had this intermittent knocking sound at idle ever since I bought it at 89k mi.

And it isn't always there.

It will come on for a bit then dissappear for a bit sometimes not to return.

It only happens at idle.

Whenever I start to drive off and put the engine under load and start driving.

It goes away.

And once I come to a stop again my car car idles whisper quiet.

Most of time after starting driving it stays away.

But once in a while it returns if I'm sitting idling for too long.

The car has always driven smoothly and great ever since I acquired it.

No hesitations or indications of friction holding the engine back or anything.

Car has always been super maintained.

Everything is in tip top shape.


Anyone have any ideas on what this may be?

I have included a video uploaded on YouTube.

The video part doesn't matter but its the sound I was capturing.

The initial portion of the video was when the car was first started and the idle was high.
So the knocking doesn't sound as prominent but its there.

Then towards the end of the video as the car warmed up and idle dropped the sound in the video becomes more prominent and audible.

Any ideas would be appreciated thx.

http://www.youtube.com/watch?v=gPdLk6lmovQ

[Bert]

My first Festy knocks like a diesel for 15-30 seconds upon startup but 7 years and 150,000 km later nothing has broken or gotten worse so I long ago gave up worrying about it. Try synthetic oil, it coats the parts. Had no effect on mine but that doesn't mean it won't affect yours. Could be you have a poorly adjusted valve lifter.
More serious; knocking results from loose wrist pins, connecting rods and that my friend will not correct itself.

[rmoltis]

Yeah I've always used synthetic oils.

And its not initial warm up noise that's for sure.

Usually it starts once its fully warmed up.
I'm assuming something inside the engine itself.

Possibly like you mentioned
Something relating to

Pistons
Connecting rods
Wrist pins etc.

The sound itself is to deep and loud to be lifters.
My last aspire at 280k had unadjusted lifter noise and it was more high pitch/ quiet/ ticky.

If it were wrist pins that would make sense why under load it doesn't make noise.
Keeping the piston firm against the connecting rod.

Any other ideas from anyone?

[rmoltis]

Talked with matt on the phone today asking questions about the intermittent knocking noise coming from my engine.

He suggested that it may be the oil squirters in the wrist pin being a lil dirty with gunk and not fully lubricating at idle.

And as load and rpm increase the oil pressure increase is able to feed through the passages to lube the pins.

He said he noticed on a few b3 rebuilds this was something he has noticed in the past during teardowns.

So he suggested towards the end of my oil change replacing 1qt of oil with 1 qt of atf and driving it for say 1000miles

And hopefully the detergents would break down the gunk that may be built up in the passages.

I should have asked before my last oil change doh!

But at least I know its nothing major.

I'll report back in 3000 miles once I've attempted to remedy the situation.

[zoom zoom]

Lifters........... Lifters man, lifters

[rmoltis]

It's too deep and loud to be lifters.

It sounds different in the video than in real life.

It sounds like a hammer tapping on something hollow

And its coming from the bottom of the engine.
Maybe in the middle even.

But Not up top.

[shadetree]

I'm going with lifters as well . Heck I have a good set I'll send ya to prove it .

[Bert]

As with most posters on here, that are looking for more challenges, you now have the excuse to start scoping around for a BPT, that doesn't knock!
I do hear you man. Tangling with motors is quite different from playing with sound systems, cleaning carpets and toying with aftermarket wheels.
Frugal as I am the upcoming Aspire B3 swap into one of my cars is going nowhere near as smooth as I would have liked. Sure, long block is the same but not much else.

[rmoltis]

Why would bad lifters only make noise when warmed up and only at idle
And only intermittently.

And then go away after driving not to return.
And leave the vehicle running whisper quiet again?

Also car runs flawlessly there's no need for replacement.

I'm planning on having dickmeyer do a performance rebuild in the next year or so
On my b3.

I just need to save up more scratch.

I've never liked the idea of an engine swap.

[Zanzer]

Install a manual oil pressure gauge and check your oil pressure at idle when hot.

[koRnhead]

Its lifters....that's just how they act. One collapses and makes noise, then refills and is fine. Wont affect drivability one bit.

[rmoltis]

Hey people this issue seems to pinpoint to bad lifters by all you and by me.
Now on certain days before oil lubes up the ticking can be loud for a few seconds.
Also when coming off accelleration to a stop.
The rpm at idle goes from 750 down to around 530-600 for a second
then goes back up to the 750 that the idle is set at

Now I want to buy new lifters to get rid of the sound.
Is this the only thing I should replace while I'm in there
or should I aim for other items as well that may be causing this noise?
How unlikely would there be say some bent rods or something?

Basically I want a list of parts for this repair.
For example
8 hla
1valve cover gasket?

[rmoltis]

So the fsm breakdown on hydraulic lash adjuster repair
Makes it seem like all I need is the;

Lash adjusters
Valve cover gasket
Adhesive for valve cover gasket.

On rockauto I was looking at The felpro valve cover gasket although it does not come with grommets others were referring to.
Do I need these new grommets?

Second there are multiple hydraulic lash adjusters.
Has anyone had any good or bad luck with any specific brand.
Ones to avoid or ones that are quality made?

And last what kind of adhesive should I use for the valve cover gasket?

Id like to order these soon.
So it there's no reply I will just buy what looks good.
I'm sure ill be fine either way.

[shadetree]

I have never used new hla s. Or adhesive ? No silicone or anything . Always swapped the bad lifter for a good on and rolled on . V/c gaskets seal very easy so no worries .
Pull the racks when it's pecking or tapping and find the weak one and replace , all is good .

[rmoltis]

I have never used new hla s. Or adhesive ? No silicone or anything . Always swapped the bad lifter for a good on and rolled on . V/c gaskets seal very easy so no worries .
Pull the racks when it's pecking or tapping and find the weak one and replace , all is good .

Cool I've heard the process is fairly simple.
I just figured id ask around.

It's nice to know the valve cover gasket is simple to set.
The fsm states the use of adhesive for the gasket but if its not needed I could go without.

And by the way a bad lifter means bad hla correct?
I'm not missing any lnfo am I?

I'm going to replace all 8 hlas just for peace of mind while I'm in there.
Just gotta order everything now thx!