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Old 11-03-2012, 09:57 AM   #1
SAWYER
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Default Engine knocking sound at idle

I have a Chrysler pacific that when at idle I hear a tap tap tap tap but it seems to go away when I am moving. I was told it could be lifters, any ideas?
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Old 11-03-2012, 10:16 AM   #2
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Does it have a rough idle? or just the clicking noise? Have you checked to see if there are any error codes in the on-board computer? Is it a high or low pitch?
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Old 11-03-2012, 10:21 AM   #3
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If it had one of the hemi engines I'd say it's just the infamous "hemi tick" (which *is* lifters), but pacificas never had those.
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Old 11-03-2012, 10:28 AM   #4
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It is either injectors doing their job when the engine is cold, or it could be the valves. My Acura gives the same noise.
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Old 11-03-2012, 10:29 AM   #5
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It idles smooth, just a loud knocking noise
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Old 11-03-2012, 10:38 AM   #6
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Could be the oil or gas in it. Had a Camaro that did that on anything but premium.
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Old 11-03-2012, 10:28 PM   #7
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It's probably just random valvetrain 'clatter.' Changing the oil may help- dirty oil can make the top end a little noisier. Fram filters used to be notorious for causing extra noise because of faulty bypass valves. Though their quality has apparently improved, I still wouldn't trust one as far as I could throw it.

If it's really loud and more slow and rythmic, you may have a problem with one specific lifter/follower. I dunno what engine is in that car or what kind of valvetrain setup it has. but typically the issue is either too much lash on a solid lifter or a collapsed hydraulic one. The extra play causes the lovely metal-slapping-against metal noise.

Get a stethoscope and see where it's louder- oil pan or valve cover(s). An issue with a rod bearing, wrist piston, or piston slap should be easier to hear with your listening device against the block or oil pan. 'Listening device' can also mean a long screwdriver, if you don't feel like plopping down a few bucks for a stethoscope.

ketchup- It sounds like you're talking about detonation/spark knock. That usually sounds less rythmic and has a little more 'rattle' to it.
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Old 11-03-2012, 10:37 PM   #8
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The 3.5L V6 had a rocker arm pin problem that made a noise.
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Old 11-04-2012, 07:58 AM   #9
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Quote:
Originally Posted by phucheneh View Post
ketchup- It sounds like you're talking about detonation/spark knock. That usually sounds less rythmic and has a little more 'rattle' to it.
I probably am. It was about 15 years ago.
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Old 11-04-2012, 08:56 AM   #10
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Never heard of spark knock at idle.
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Old 11-04-2012, 09:06 AM   #11
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Changing oil viscosity in my girlfriend's car solved a similar problem for her. YMMV. Best of luck.
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Old 11-04-2012, 09:25 AM   #12
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Most common source for the noise would be the rocker shafts or Manifold Tuning Valve .
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Old 11-04-2012, 10:48 AM   #13
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Toss in some "motor honey", that stuff will quiet anything down, then trade in van. How many miles we talking about here?
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Old 11-04-2012, 11:09 AM   #14
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I'd say it is just lifter tick and not really worry about it. If it was rod, mains, or piston slap it wouldn't go away when moving. Piston slap would go away or get better as the engine heats up though, so does lifter tick usually. My miata sounds like damn diesel thanks to lifter tick when cold or after beating the crap out of it at autox.
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Old 11-04-2012, 09:20 PM   #15
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60k
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Old 11-05-2012, 09:04 PM   #16
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Fords with the 5.4 and 4.6L with variable cam timing are well known for having a cold tick.

Indeed, Ford now recommends that if you don't like the tick, you should change from 5W20 to 10W40 weight oil.

I'd suggest changing your oil to a slightly higher value - if the tick goes away, it's really nothing to worry about it.

Injectors also tick. You'll also hear a tick if you have a cracked or broken exhaust manifold, and it goes away when then manifold heats up and seals again.

With all the rotary parts on an engine, without something more specific, it's hard to guess what it might be.
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Old 11-07-2012, 08:41 AM   #17
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What oil do you use? I believe the 3.5 calls for 10w30. Generally a pretty good engine, so its more than likely nothing to really worry about, but its hard to say without hearing it.
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Old 11-07-2012, 11:11 AM   #18
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Quote:
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60k
Shoot, keep it for sure..
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Old 11-07-2012, 12:21 PM   #19
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change your oil.
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Old 11-07-2012, 12:41 PM   #20
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If it's the rocker arm pin deal, he'll know for sure in a little while.
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