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Discussion Starter #1
Hello everyone

I have a 2007 Wrangler. Lately when starting the engine while cold there is an audible knocking that doesn't last more than two seconds. When the engine is already warm, there is no knocking. This is pretty new and worries me, i'm not sure what it can be causing this.
Any ideas?

Thanks
 

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Check the exhaust manifold for cracks.
 

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Discussion Starter #4
Doesnt sound like a problem with the manifold, but wouldnt hurt to take a look. I havent heard of piston slap, but certainly sounds plausable. Geuss I should take it in to be looked at, just dont have the money too.
 

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Clay is the oil level good? Is the oil fresh? What weight oil is in it?
 

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Needs better gas! Fill with high-test. Hope it improves, because nobody wants to think about anything else. $$$$
 

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Discussion Starter #7
Oil level good is good, I checked it. I keep up with scheduled changes. Oil is a manufactured recomendations.
 

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Discussion Starter #8
The book says 87 for gas, doesnt need a higher grade
 

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At least try a different brand. Knock off gas (AKA watered down), will sure give you a knock. It's not always just pings.
 

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Yukon Cornelius
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i bet its piston slap...they are making pistons shorter and shorter in an effort to make them more efficient. a shorter piston is a less stable piston but the problem quickly goes away once a little warm
 

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Discussion Starter #11
once again, I havent heard of a piston slap, but is that somthing to be concerned about?
 

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CountryGun said:
.... Knock off gas (AKA watered down), ...
There is no such thing. In fact, all gasoline in Georgia is sourced from only two places.

Do you have the V8 engine? You do not mention the Oil Change Period. How long has the oil been in there, what filter is used, and what Grade of oil?

Three things.... One, your oil filter backflow/drainback valve may be allowing the oil to drainback into the crankcase under shutdown overnight. Until oil pressure is built and the engine gets all its oil passages closed, it would also manifest itself as "piston slap", but could be your timing chain tightener. (This is most likely. Change your oil filter and brand.)

Two, Indeed, if you have the same engine family as my Dodge (4.7 l) you could have a broken manifold. I did, and it expanded to close off the craack very quickly after startup. There were several broken studs and it is a known problem with that family of engines.

The other thing it can be is a worn out lifter spring with a higher mileage engine. Once full oil pressure is acheived, it goes away and is not really a problem.
 

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Match10 said:
CountryGun said:
.... Knock off gas (AKA watered down), ...
There is no such thing. In fact, all gasoline in Georgia is sourced from only two places.
I'm sure you're right Match, you usually are. But, please don't tell me cheap gas won't cause a knock.

On the other hand, sometimes I just chime in with something so I can stay abreast of what the answer turns out to be. :sly: I'll bug out now. :runaway:
 

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Discussion Starter #16
CountryGun said:
Match10 said:
CountryGun said:
.... Knock off gas (AKA watered down), ...
There is no such thing. In fact, all gasoline in Georgia is sourced from only two places.
I'm sure you're right Match, you usually are. But, please don't tell me cheap gas won't cause a knock.

On the other hand, sometimes I just chime in with something so I can stay abreast of what the answer turns out to be. :sly: I'll bug out now. :runaway:
Come to think of it, since moving recently, I've been stopping at the local BP for gas... :cantsay:

Thanks for the advice everyone. I will be doing a tune up, another oil cange with different products, and try a different brand of gas. Hopefully it isn't anything worse than these.
 

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CountryGun said:
I'm sure you're right Match, you usually are. But, please don't tell me cheap gas won't cause a knock.
It's my mechanical engineering background.... :wink: I really do not think that sub-octane fuel will cause a knock under cold startup, only under load. (At least that is what I learned 35 years ago in engines class/lab.... :shattered:

OP.... Consider the oil and filter change first. I am sure that is the place where it is most likely the fault lay.
 

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Match10 said:
There is no such thing. In fact, all gasoline in Georgia is sourced from only two places.
:righton:

I've talked to several fuel tanker drivers and they've said the same thing. All gasoline is the same. They all have to meet the same minimum requirements. Some brands have additional additives added to them when they unload the fuel into the underground tanks. (i.e. Techron)

There's a large pipeline that brings all the gasoline from Texas to Georgia.
 

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Check your battery posts for corrosion.

Brands of gas doesn't matter, now I do like to buy gas at the newest station to keep from getting contaminated gas.

Clay on the oil filter...When you are shopping for the filter, buy one with a rubber insert behind the holes. I know it sounds odd but Match hit on it(it is a drainback valve, this keeps some of the oil in the top of the engine), you can also stick your finger up in the screw-on hole and feel around and feel to see if it has the valve. Some filters have them some don't. Once you see one side by side with one that doesn't have it, it's easy to spot.

Also no Wrangler has ever left the factory with a V8.
 

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Discussion Starter #20
mountainpass said:
Check your battery posts for corrosion.

Brands of gas doesn't matter, now I do like to buy gas at the newest station to keep from getting contaminated gas.

Clay on the oil filter...When you are shopping for the filter, buy one with a rubber insert behind the holes. I know it sounds odd but Match hit on it(it is a drainback valve, this keeps some of the oil in the top of the engine), you can also stick your finger up in the screw-on hole and feel around and feel to see if it has the valve. Some filters have them some don't. Once you see one side by side with one that doesn't have it, it's easy to spot.

Also no Wrangler has ever left the factory with a V8.
Thanks, I will check into that as well. Lol, ya wranglers don't come in V8.
 
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