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Old 04-27-2018, 11:49 AM   #1  
MR_Lapoint
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Default 15% Decrease in Compression Cylinder 2

So recently i bought a 2010 mustang GT. With 46k miles. I drove it 300 miles back home with no issues. It ran like a dream. But after 2 days home, the check engine light came on at the drive through while idling. I had noticed a slight like popping sound in the exhaust right before the light came on. The difference i hear in the exhaust goes away when i acccelerate. But i here it more rapid as the rpm drops. Also it is gotten sluggish in the low rpm range.

Anyways i pulled the codes and got two faults, cylinder 2 misfire and “keep alive memory” fault.
I took it to the dealer and they navigated the problem to a cold start issue. Well they kept the car for 4 days and couldnt duplicate the problem. After i got a little frustrated with their lack of communication and problem solving. They called me the next morning to tell me they had a 15% decrease in compression on cylinder 2.

So they recommended a carbon cleaning, tune up and a reprogram of the computer. Which i let them go ahead and do. $600.

Ive had the car less then 24hrs. No light has come up yet. But im still noticing the popping sound hear and there, it does go away and come back. Also the car just has no torque and sometimes feels like it is choking if i try to take off easy... i just dump a bottle of engine restore in it. And bought a new vct solenoid for that head, but hasnt come in the mail yet.

Anyone have any suggestions?

Last edited by MR_Lapoint; 04-30-2018 at 12:58 PM. Reason: Title was misleading
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Old 04-27-2018, 10:30 PM   #2  
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Your title says 15% compression, then later a loss of 15%... HUGE difference.
If there was 15% compression in cylinder #2, you have a serious problem there,
that no cleaning and reprogram is going to fix.

You said the CEL came on, what was the code? Without that, this is all guess work...
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Old 04-28-2018, 12:53 AM   #3  
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Originally Posted by 08'MustangDude View Post
Your title says 15% compression, then later a loss of 15%... HUGE difference.
If there was 15% compression in cylinder #2, you have a serious problem there,
that no cleaning and reprogram is going to fix.

You said the CEL came on, what was the code? Without that, this is all guess work...
When i pulled the codes, it was a misfire in cylinder 2 and a “keep alive memory”(p1633) fault.
Btw driving home from work today. CEL came back on. So whatever ford said they did, didnt work and i think they just milked the hell outta me for nothing. Will be calling to conplain in a few hours.
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Old 04-28-2018, 01:49 AM   #4  
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The code is a Keep alive power voltage too low. Open circuit or faulty PCM.
It's supposed to be whatever the battery voltage is. There is a fuse for this,
but may also run something else; like, a Ford Fiesta, it's with the horn fuse...

This is the circuit that supplies constant battery voltage to the keep alive memory portion
of the PCM so it can retain information regarding fuel control, idle control and transmission
control adaptive strategies... If the battery is disconnected or voltage drops below 10.5 volts
this code will be set. If the battery has not been disconnected then the circuit will need to be
checked for opens or high resistance in the wire,shorts,blown fuse, high voltage r/f interference
from ignition or charging system components, or the PCM being being faulty itself.

You need to find which pin on the ECU is the KAPWR wire, and check voltage...

This can be intermittent too, chaffed wire, or bad ECU...
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Old 04-28-2018, 06:33 AM   #5  
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Quote:
Originally Posted by 08'MustangDude View Post
The code is a Keep alive power voltage too low. Open circuit or faulty PCM.
It's supposed to be whatever the battery voltage is. There is a fuse for this,
but may also run something else; like, a Ford Fiesta, it's with the horn fuse...

This is the circuit that supplies constant battery voltage to the keep alive memory portion
of the PCM so it can retain information regarding fuel control, idle control and transmission
control adaptive strategies... If the battery is disconnected or voltage drops below 10.5 volts
this code will be set. If the battery has not been disconnected then the circuit will need to be
checked for opens or high resistance in the wire,shorts,blown fuse, high voltage r/f interference
from ignition or charging system components, or the PCM being being faulty itself.

You need to find which pin on the ECU is the KAPWR wire, and check voltage...

This can be intermittent too, chaffed wire, or bad ECU...
Im completely clueless when it comes to electrical, but could this be the result of a decrease in compression?
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Old 04-28-2018, 02:25 PM   #6  
08'MustangDude
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A decrease in compression is a mechanical failure, like I said before; Valve issue for that cylinder,
or the compression rings on that piston, or even leaking past a spark plug...

VCT solenoid is just for variable valve timing. If there was a timing issue, then all cylinders
would be effected. However, the way it's made, if the VCT fails, you just don't have the
VVT anymore on that bank, and lose HP because it acts like a non VVT motor.

Also, sorry to say, you paid $600 for nothing unless they took the head off and manually
cleaned it. Due to the fact that these motors are NOT direct injected, there would be
no need for that anyway. Direct injection motors suffer carbon build up on the valves
because the fuel does not wash over the intake valves like multi-port does. When the
carbon becomes an issue, it causes bad valve seating, they don't close all the way and
you lose compression in the effected cylinder(s). You have to remove the head to clean it.
This is a common issue with VW/Audi/BMW... Mostly because of continuous short trips.
I got over 135,000 on my '15 TSI, and it's fine. I had 243,000 on my former '13 TDI and
never had the issue, but, I drove 460+ miles a day, 4-days a week.

SMPFI motors, the injectors are behind the intake valves, so they're washed.
Not that carbon can't be an issue, but that would also mean the engine's running
hotter than it should. Cleaning these means spraying something in the intake
as your keeping the engine at 2000 RPM. Most people use seafoam. Or, putting
it in the fuel so it sprays over the valves going in. If you have a bad injector seal,
it would not effect compression because it's behind the intake valve.

Direct Injection, the injectors are in front of the intake valves, and spray fuel directly
into the cylinder. The valves are not washed, and carbon builds up much faster.
Carbon builds up on the valve stems real fast, and also the valve seat. You can still
spray something into the intake to clean the intake valves, but usually by the time
there is a problem, it's too late. It may not work because the carbon is so thick
and hardened up. If you were doing this every month since you bought it, then
it can help prevent it, that and a catch can... On top of this, because the injectors
are in front of the intake valves, if a FI seal is bad, then you can lose compression
because it's leaking that air and fuel past the injector, right into the engine bay.

The only thing electrical that could cause a loss in compression would be if these motors
had MDS or other cylinder shut-down feature that isn't working right on that cylinder.

SOON, we will have variable compression engines, so then here's a whole new list of
possible problems to deal with.
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Old 04-28-2018, 02:41 PM   #7  
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So do you have any ways for me to troubleshoot my own issue? To see if its a bad injector seal or whatever. Im sorry if im sounding slow but you said alot and im not to sure what pertained to my engine exactly. Im trying to follow. But please bear with me.
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Old 04-28-2018, 06:00 PM   #8  
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Quote:
Originally Posted by MR_Lapoint View Post
So do you have any ways for me to troubleshoot my own issue? To see if its a bad injector seal or whatever. Im sorry if im sounding slow but you said alot and im not to sure what pertained to my engine exactly. Im trying to follow. But please bear with me.
well i just drove to the store to get some food, so now its trying to run hot!!?? This is getting frustrating and ford dealer said they talk to me monday... so i guess ima park it and try to resolve this issue i have with them and my $600 wasted.. refund maybe! I hope
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Old 04-28-2018, 08:36 PM   #9  
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Quote:
Originally Posted by MR_Lapoint View Post
So do you have any ways for me to troubleshoot my own issue? To see if its a bad injector seal or whatever. Im sorry if im sounding slow but you said alot and im not to sure what pertained to my engine exactly. Im trying to follow. But please bear with me.
Your engine is SMPFI, not Direct, so if they charged you $600, all they did was
rev the motor to 2000 and spray something into the intake. You won't be leaking
past a fuel injector seal with SMPFI.

Oh, one thing I did not think of, was a head gasket. Compression can leak through
that. Check to see if your coolant reservoir is bubbling, you will see it even at idle.
There should be no air going to the reservoir, so of you see bubbling from it, then it's
a head gasket. The misfire can be coolant leaking into the chamber, it would be
pulled in at the beginning of the intake stroke, end, or both.

Wants to run hot now? CHECK YOUR COOLANT! If the coolant reservoir is empty,
that's a sign of head gasket failure. It has to have gone somewhere, and if not on the
ground, then it went into the motor.. My son bought a Ford from a lot, and had to
fill the reservoir 3 times, and I saw it IMMEDIATELY! Had to take the car back...
THEY said it was a lower timing chain cover, lying jag-offs, no, it was as head gasket.
We called the people THEY took the car to, and they told us it was the head gasket,
and the dealer lied to us, so it went back...

Bad valve lash can also cause the compression loss, but as I said, it's a valve
issue, regardless of the cause... That means the one of the valves are not closing
all the way on the compression stroke.

Last edited by 08'MustangDude; 04-28-2018 at 08:39 PM.
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Old 04-28-2018, 09:05 PM   #10  
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Quote:
Originally Posted by 08'MustangDude View Post
Your engine is SMPFI, not Direct, so if they charged you $600, all they did was
rev the motor to 2000 and spray something into the intake. You won't be leaking
past a fuel injector seal with SMPFI.

Oh, one thing I did not think of, was a head gasket. Compression can leak through
that. Check to see if your coolant reservoir is bubbling, you will see it even at idle.
There should be no air going to the reservoir, so of you see bubbling from it, then it's
a head gasket. The misfire can be coolant leaking into the chamber, it would be
pulled in at the beginning of the intake stroke, end, or both.

Wants to run hot now? CHECK YOUR COOLANT! If the coolant reservoir is empty,
that's a sign of head gasket failure. It has to have gone somewhere, and if not on the
ground, then it went into the motor.. My son bought a Ford from a lot, and had to
fill the reservoir 3 times, and I saw it IMMEDIATELY! Had to take the car back...
THEY said it was a lower timing chain cover, lying jag-offs, no, it was as head gasket.
We called the people THEY took the car to, and they told us it was the head gasket,
and the dealer lied to us, so it went back...

Bad valve lash can also cause the compression loss, but as I said, it's a valve
issue, regardless of the cause... That means the one of the valves are not closing
all the way on the compression stroke.
yea i just went and checked reservoir, no bubbles, no oil in there either.
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