Our first DTC P0308

[Locksmith]

This is a 2017 GT convertible with 62K miles. No performance mods yet, nothing but routine maintenance. I have the factory manual on CD and my mechanic neighbor at work has an Autel.

My gut reaction was the coil. It wasn’t. Read about the plastic flap in the intake that breaks so I borrowed his Autel to run some tests. I had someone tell me that the two vacuum actuators on the back of the intake are what control the air/fuel mixture but on the Autel they are called intake manifold runners. It responds to the test and I can hear a change when I turn them on and off.



The two air/fuel tests are bank one and bank two. The car responds to bank one but nothing for bank two. My question is, does this engine only use bank one or is this a definitive answer that I need a new intake?

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[GT Pony]

Why do you say bank 2 isn't responding? Looks like it's basically doing what bank 1 was doing.

If you drive around and watch the fuel trims for bank 1 and bank 2, what do you see?

 

[Locksmith]

Sorry if it's not clear enough. I didn't realize I was cutting off the bottom of the screen. This is among the active tests you can perform with the Autel. When I choose bank 1 and hit decrease or increase, the car goes along with the Autel. The gauge matches the air fuel ratio that the Autel is commanding. When I chose bank 2 I can adjust it all the way to it's high and low limit and the car stays around 14/1. What I don't understand is, usually when manufacturers use the term bank 1 and bank 2 they're talking about O2 sensors. It was just a shot in the dark that maybe bank 1 was one side of the intake and bank 2 was the other. This was an attempt to figure out if the flaps in the intake are broken or not without removing the intake. Apparently it's common and will trip P0300 and P0308. I went ahead and bought intake manifold gaskets and I'm going to remove it this weekend to see.

I have not yet driven it while watching live data. Have to arrange help.

 

[Locksmith]

Bingo!

 

[Locksmith]

Reading more in the manual and found this in the description and operation section. Ford is actually calling the two intake manifold runner controls bank 1 and bank 2. Bank 2 is the side that's broken on ours. Is that a coincidence? I'm really confused and curious because the only time I saw the IMRC moving was with the IMRC on/off test. The PCM can monitor its position but only on the outside. When they break this way, the PCM has no idea. I'd love to know if this is a round-a-bout way of diagnosing it. Anyone have any idea what the Autel telling the car to do during the air/fuel test?

 

[silverbullet85]

Bank refers to side, bank 1 is passenger side and bank 2 Is drivers side. When a code refers to bank 1 or 2 it could reference a lean condition on one bank or it could be a bank 2 upstream o2 sensor code, it just helps narrow down the side of the engine or exhaust the problem is on

 

[Locksmith]

By code, do you mean DTC? The P0300 and P0308 does not differentiate between bank 1 or 2. The Autel air/fuel test references bank 1 and 2 and the factory manual references the IMRC bank 1 and 2 but I have no idea if they are related. I'm wondering if there is a link here because when I ran the air/fuel tests, the vacuum actuators did nothing.

 

[GT Pony]

From a Google search, in general P0300 indicates that two or more cylinders are experiencing misfires. P0301 means cylinder 1 misfire detected, P0302 means cylinder 2 misfire detected, P0303 means cylinder 3, etc up to P0308 for cylinder 8. I'm assuming Ford uses the same DTC correlation.

 

[Locksmith]

Fords possible causes. I love 1/8 tank... really!?

 

[Locksmith]

This is mildly infuriating. Stock intake is on national backorder from Ford. When we were car shopping, my main argument for a new car knowing they are all plastic junk at this point was get a high production domestic so parts would be available. Every aftermarket solution requires other modifications and tuning. Does anyone have a working 2017 GT stock intake laying around cause you upgraded?

 

[GT Pony]

This is mildly infuriating. Stock intake is on national backorder from Ford. When we were car shopping, my main argument for a new car knowing they are all plastic junk at this point was get a high production domestic so parts would be available. Every aftermarket solution requires other modifications and tuning. Does anyone have a working 2017 GT stock intake laying around cause you upgraded?

What exactly fails to cause the intake butterflies not to open? Is it a simple mechanical failure (like the linkage or similar) that can be fixed and/or improved in the garage?

 

[Locksmith]

It's the rotating shaft that goes through the intake that all the flaps are controlled by. The vacuum actuators are connected to a linkage rod that converts linear motion to rotational. That shaft is broken just inside the intake after the linkage rod. I'm paraphrasing here but if I understand it correctly, the flaps are closed below 3000 RPM for fuel economy. Open above 3000 for power. The vacuum actuator and sensor are working properly but the problem is, the sensor is at the linkage end so it doesn't have a clue what the actual flaps are doing. The PCM thinks they are working and adjusting air/fuel but the flaps on bank 2 (driver side) are not moving so it misfires.

I found a stock intake on FB that I'm probably going to get this weekend. If it works out, I will tear mine apart.

 

[Locksmith]

Good to go with the new (20k used) intake. Gotta swap some stuff over and install new gaskets. I already drew blood so everything should go perfect from this point.

 

[Mike Pfeifer]

From a Google search, in general P0300 indicates that two or more cylinders are experiencing misfires. P0301 means cylinder 1 misfire detected, P0302 means cylinder 2 misfire detected, P0303 means cylinder 3, etc up to P0308 for cylinder 8. I'm assuming Ford uses the same DTC correlation.

Yes, those are OBD-II P-codes and they are used by every manufacturer, by law. Some manufacturers also use their own proprietary codes in addition to the standard OBD-II P-codes.

 

[Locksmith]

It's back together and running with no CEL or DTC's. That was actually a really easy job. Have to have a torque angle gauge if you're going to follow Fords torque specs. But otherwise, all I needed was a set of new gaskets and well... a new freaking intake. Good luck with that if you want stock. National backorder from Ford. I found one on FB for $100.

I have verified with my old intake that if you have an endoscope and you remove the throttle body, you can get the endoscope up the intake runners and see if the flaps are moving or not. It's difficult to move them manually with the intake installed so I'd suggest a vacuum pump.

I took the vacuum actuators and sensors off the back to see what broke and it was actually a metal rod. I was surprised and a bit disappointed. I expected the failure to be something that was made out of plastic. Go figure.

With a working IMRC I did the air/fuel test again and got the same results.

The intact side and the broken side.

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