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07 Mustang GT low pressure, pcm problem?

Old 06-12-2019, 02:39 PM
  #1  
Luis Macias
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Default 07 Mustang GT low pressure, pcm problem?

Good day everybody.

I want to be as short as possible. I'm repairing my 07 GT (I bought it with some issues).
Well the principal problem is engine knock when warm, oil pressure down to 8~10psi, no DTC codes.

things that I have done (possible solutions as I had read in the forums.):

replace cam phaser (OEM), the others were blocked with a nut, VCT Solenoids (OEM), alternator, the old had problem with diode. result, no changes.

replace oil pump (for oil pressure low) with a melling 10340, result, no changes.

The Throttle body is new (OEM), all engine gaskets replace with new ones, main bearing, rod bearing in good state, replace rocker arms... and nothing...

6 months and nobody finds out the problem with my car. Neither specialized mechanics nor ford dealers. XD,

Last week, talking to a friend, he told me that the problem is probably due to a bad ground or a bad PCM. Then I was looking for problems with the wires and I found these problems in the fuse box, do you think that is the cause of the big problem with the low oil pressure?


Here it seems that they put the relays on the outside (Cooling fan high and low)

Here it seems that they pulled the cable, but from where?


These issues can cause low oil pressure and knock sound or is directly the PCM?

Thanks for you attention.
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Old 06-13-2019, 02:20 PM
  #2  
Derf00
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The nice thing about oil pressure is that is is purely mechanical....

Low oil pressure is usually caused by a bad oil pump (you already replaced) or worn rod/main bearings (engine knock can = rod knock) which means you'll need to drop the pan and inspect them. If the rod or main bearings are worn or have strange wear marks, you can try just replacing them and see if the pressure comes back up. Once that is back up then you can look at the other items if they are still present. Since you replaced the oil pump, how did the pickup tube screen look? A clogged one will lower your oil pressure.

By the way, the VCT solenoids and Cam Phasers all WORK OFF OF the oil pressure. Meaning they are affected by it but do not impact it. . So, if you have low oil pressure, there a host of problems you can have that are related.

IDK about the wiring mystery. One problem at a time.
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Old 06-13-2019, 04:03 PM
  #3  
Luis Macias
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Low oil pressure is usually caused by a bad oil pump (you already replaced) or worn rod/main bearings (engine knock can = rod knock) which means you'll need to drop the pan and inspect them.
the rod and main bearing already was inspected by 3 different person and they told me no issues (worn or strange marks), the pan is very clean, the pickup tube screen clean.

About VCT, when start engine oil pressure is about 30psi, then drop to 8~10psi at hot but if I disconnect the VCT the oil pressure doesn't go down and never knock. That's why I mentioned the vct.

About the wiring, apparently it is a improvised fix for the Cooling fan high and low relays.

Thanks
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Old 06-14-2019, 01:14 PM
  #4  
Derf00
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What weight of oil are you suing? I know OEM is 5W-20 but have you tried 5W-30? Here is AZ I've used 5W-30 since my first oil change and never looked back. I recently had the valve covers off to replace the gaskets and the valve train looked new with 90K miles on it.

There's a similar thread here but no resolution. It will give you ideas on what else to check out.

https://mustangforums.com/forum/2005...oid-issue.html
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Old 06-14-2019, 09:10 PM
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bl817
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O rings on the timing chain tensioners are probably shot. that's the first place the oil goes on its way up to the cams. would have been a good time to replace them when the timing cover was off.
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Old 06-18-2019, 02:16 PM
  #6  
Luis Macias
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Originally Posted by Derf00 View Post
What weight of oil are you suing? I know OEM is 5W-20 but have you tried 5W-30? Here is AZ I've used 5W-30 since my first oil change and never looked back. I recently had the valve covers off to replace the gaskets and the valve train looked new with 90K miles on it.

There's a similar thread here but no resolution. It will give you ideas on what else to check out.

https://mustangforums.com/forum/2005...oid-issue.html
First 5w-20 then I changed to 5w-30, there is no difference.
About the thread of the vct solenoid, I saw it a while ago and I've already tried everything
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Old 06-18-2019, 02:28 PM
  #7  
Luis Macias
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Originally Posted by bl817 View Post
O rings on the timing chain tensioners are probably shot. that's the first place the oil goes on its way up to the cams. would have been a good time to replace them when the timing cover was off.
Yes, the tensioners of the timing chain were replaced, the mechanic thought that this could be the problem, but there were no changes.
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Old 07-08-2019, 12:37 PM
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Luis Macias
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Well, time to update...

Since I did not know where to start, I started checking the harness, because I was surprised by the broken connector.
Well, first what I did was discover that I was connected there, and I found that it was the Anti Theft Hood Latch Switch.

I bought it and I put it on, then I start my stang and now my scanner show me two DTC codes,P0345 and P0349.
As I said before, the alternator had already replaced it, cam phasers, VCT solenoids and camshaft position sensors too. I went to see the manual and followed the procedures of DR: Camshaft Position (CMP) Sensor.

I start with DR1, DR2... up to DR16 "CHECK FOR A SHORT IN THE HARNESS BETWEEN THE PCM AND THE CMP2 SENSOR"


From Sigrtn to negative terminal there is 0.2 ohms, This means that there is a short circuit, right? now to look for it.
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