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Engine knocks when it warms up...

Old 09-07-2011, 07:31 PM
  #1  
aloredo07
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Default Engine knocks when it warms up...

I posted before about this problem but i just want to update you guys on the situation, hopefully i can get some answers. When i start the engine cold it idles fine, but as it warms up to operating temp it knocks loud. I've check the oil and its clean, i dont see any metal shavings in it. When i come to a complete stop and i try to take off in 1st gear it is very slow and then it picks up the speed. The knocking still continues as i'm driving.
I took my car to three different shops and all three gave me a different diagnosis.

First shop said my car had low oil pressure but the gauges in the dash were reading normal. They replace both solenoids and the knocking continued. Then they wanted to take apart the engine because they couldnt find any problems and they felt they needed to dig in. I took my car back before they started to take it apart. This happen for about three wks and i couldnt get a solid answer from these guys.

Second shop said it was the tensioners. The mechanic called another mech from a different shop to get a second opinion before he replace the tensioners and the other mechanic said it was a crack head or piston. So I get a call and the mech tells me that i'm better off buying a different engine. I ask how much it would cost to check if it was a head or piston and he told me around $1700.

So i decided to just take the car back to the dealer and they told me that it sounded like a main bearings but they weren't sure until they pulled the engine and check it. This would cost me around $2500. Just to pull out the engine and check the main bearings.

My car is back in my garage. It has not been driven since the knocking started. I've had to tow it to each shop. If any of you guys had a similar problems please help me out. Thanks
Specs:
2008 mustang Gt
Mac LT headers/ Pro chamber/ SLP axlebacks
Injen CAI
Predator Tuner
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Old 09-07-2011, 08:24 PM
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grabber blue gt
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I always wondered what I would do if I blew my motor or something like that. I was just looking online last night and there was a 4.6L out of a 2010 mustang for $2500 obo with 14k miles on it. If they cant diagnose it I would personally just buy that.
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Old 09-07-2011, 09:00 PM
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aloredo07
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yeah thats my last option. i bought my car brand new and it only has 62k miles on it. I wasnt driving the car when the knocking started so i can't really say how it happened. I would still like to see if its repairable but $2500 is not bad for that engine. Thanks a lot
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Old 09-08-2011, 09:33 AM
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modru2004
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Originally Posted by aloredo07 View Post
I posted before about this problem but i just want to update you guys on the situation, hopefully i can get some answers. When i start the engine cold it idles fine, but as it warms up to operating temp it knocks loud. I've check the oil and its clean, i dont see any metal shavings in it. When i come to a complete stop and i try to take off in 1st gear it is very slow and then it picks up the speed. The knocking still continues as i'm driving.
I took my car to three different shops and all three gave me a different diagnosis.

First shop said my car had low oil pressure but the gauges in the dash were reading normal. They replace both solenoids and the knocking continued. Then they wanted to take apart the engine because they couldnt find any problems and they felt they needed to dig in. I took my car back before they started to take it apart. This happen for about three wks and i couldnt get a solid answer from these guys.

Second shop said it was the tensioners. The mechanic called another mech from a different shop to get a second opinion before he replace the tensioners and the other mechanic said it was a crack head or piston. So I get a call and the mech tells me that i'm better off buying a different engine. I ask how much it would cost to check if it was a head or piston and he told me around $1700.

So i decided to just take the car back to the dealer and they told me that it sounded like a main bearings but they weren't sure until they pulled the engine and check it. This would cost me around $2500. Just to pull out the engine and check the main bearings.

My car is back in my garage. It has not been driven since the knocking started. I've had to tow it to each shop. If any of you guys had a similar problems please help me out. Thanks
Specs:
2008 mustang Gt
Mac LT headers/ Pro chamber/ SLP axlebacks
Injen CAI
Predator Tuner
well im just tossing out an idea from things ive learned on these awesome forums. maybe im a bit off base but here it is anyway.


here are three key things to look at, you say it ran fine cold, it was after the engine was hot/warmed up that the knock started occuring. you also listed a predator tuner, so im assuming a tune.

generally knocking is heat related. this is why heat soak is such a problem at the track. your ecu has to retard timing as the engine heats up to prevent knocking. this also hurts performance, especially on boosted vehicles. this is why this is such a popular discussion, there are numerous threads on it here.

first: is it possible that there is an issue with the knock sensor of the vehicle? is possible that its not functioning as it should therefor not retarding the timing and you end up with knocking.

second: you have a tune, is it possible that your tune has LOCKED the timing so it can't be automatically adjusted by the ecu.

third: is the knock happening on all cylinders, or specific ones.

Forth: have you removed you tune and gone back to stock? the less variables in the equation the easier it will be to troubleshoot.

fifth: you have a programmer, have you used it to pull codes? the ecu should be throwing some codes? what are they?

thats my little troubleshooting list and
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Old 09-08-2011, 10:33 AM
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Roy_R
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^^^ Makes sense and cheaper than pulling the engine!
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Old 09-08-2011, 01:26 PM
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aloredo07
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yes i do agree its cheaper. the code that is showing is p0345. It has to do with the vct solenoid. i've repplace both and its still showing the same code. i am going to load the stock tune back in the car and see if the knocking goes away. U make a lot of sense modru2004. I will rule out all the possibilities that u just listed then i'll update u guys with the results. Thanks again
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Old 09-08-2011, 04:28 PM
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modru2004
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http://www.obd-codes.com/p0345

thats a good article to read on that code.

an excerpt with important things bolded:

"This indicates that a problem was detected in the camshaft position sensor circuit of bank 2. Since it says circuit, that means the problem could lie in any part of the circuit - the sensor itself, the wiring, or the PCM. Don't just replace the CPS (camshaft position sensor) and think that will definitely fix it."

gotta love electronics lol. so many things that can go wrong. if your stock tune didn't help matters id inspect/clean your wiring for the cam shaft sensor as necessary. if the stock tune doesn't help and you have replaced both cam shaft position sensors, and the wiring looks fine/connectors are clean then it would seem the next place to look would be the pcm itself.

this is all sounding like an electronic issue and not an issue with the engine itself. which means pulling the engine or replacing it with another would do you absolutely no good.


edit: also this http://www.howstuffinmycarworks.com/VCT_Solenoid.html dealing with the modular 5.4 3vbut should be relevant to the 4.6 3v as well.

the cam shaft position sensors are not the same as the vct solenoid which i believe you said you replaced. definitely check those first.

Last edited by modru2004; 09-08-2011 at 04:41 PM.
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Old 04-05-2014, 02:41 PM
  #8  
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Default Similiar issues as aloredo07

I have an 05 GT that has similar issues. After I idle for long periods of time it will start to knock. If I rev it up or start moving along the noise will go away. I can drive it normally for hours & it will not occur at all. It will how ever hesitate a little when I take off sometimes spit & sputter a little too. The oil is all good, no metal shavings, coolant is also good. It does not smoke nor burn any oil between changes. I am putting it in the shop in a week to get it diagnosed but would like to get a little idea about what I could be looking at so they don't try to bilk me. Me being a woman many shops sure will try it. My car is all stock. Could it be vacuum issues, oil pressure issues or sensors? Someone please help.
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