MidwestBoater
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2016 Expedition XLT with 75,*** miles
I monitor a few gauges, such as boost pressure/vacuum with an old android phone with the Torque App on it, connected by bluetooth to an OBDII reader. Also, I'm running the SCT 89 octane tow/performance tune.
Now on to the story. So, I first got this code about 3 weeks ago while towing my boat up a long gradual hill, I was making about 13lbs of boost climbing the hill, then all of the sudden it dropped to 5lbs and felt like I had a 4 cylinder. No check engine light. I pulled off the highway and pulled the codes, finding a P0299 "low boost pressure" code. I cleared the code, restarted the truck, and continued on my merry way with no further issues.... until the trip home later that day.. same spot on the highway, a long gradual hill, all of the sudden I have no power, until I pull off the highway, clear the P0299 code, restart the truck, and proceed with my drive.
What I discovered is that this code is set when the PCM sees a 4lb or greater drop in pressure (from what it expects to see) for 4-5 seconds or longer, when the code is set the PCM goes to limp mode, which limits boost pressure to about 5lbs until the code is cleared.
First I checked all of the pressure side clamps on the turbos, the intercooler, throttle body, etc, then checked all of the hoses that go to the wastegates and wastegate actuator solenoid that is on top of the intake manifold. Nothing seemed loose, no holes or cracks in any hoses, etc. Problem persisted when towing.
As a couple of weeks went by I noticed in my daily driving that the truck was getting more and more "piggy", needing to rev higher in the RPMs to get up to speed, boost pressure not getting much over 15 at full throttle (it hits 20 with the tune), and really slow to build pressure in normal daily driving.
At this point I was thinking that it's either a faulty wastegate, wastegate actuator solenoid, or blow off valve (ford calls it a turbocharger intercooler valve). The two cheapest of those parts are the wastegate actuator solenoid ($28) and the blow off valve ($58). Now the blow off valve has a rubber diaphragm inside, which from what I found online can develop a tear, so that's the part I was hoping caused the problem, and if the tear were enlarging, that would explain why the problem seems to be getting worse. So I ordered part # AA5Z-9U465-A and upon removing the old one last night I could immediately see the tear in the rubber diaphragm. Bolted the new part in place, reconnected the electrical connector, took it for a test drive, and WOW is the power back!
Hope his helps someone save a lot of troubleshooting time and/or money.
I monitor a few gauges, such as boost pressure/vacuum with an old android phone with the Torque App on it, connected by bluetooth to an OBDII reader. Also, I'm running the SCT 89 octane tow/performance tune.
Now on to the story. So, I first got this code about 3 weeks ago while towing my boat up a long gradual hill, I was making about 13lbs of boost climbing the hill, then all of the sudden it dropped to 5lbs and felt like I had a 4 cylinder. No check engine light. I pulled off the highway and pulled the codes, finding a P0299 "low boost pressure" code. I cleared the code, restarted the truck, and continued on my merry way with no further issues.... until the trip home later that day.. same spot on the highway, a long gradual hill, all of the sudden I have no power, until I pull off the highway, clear the P0299 code, restart the truck, and proceed with my drive.
What I discovered is that this code is set when the PCM sees a 4lb or greater drop in pressure (from what it expects to see) for 4-5 seconds or longer, when the code is set the PCM goes to limp mode, which limits boost pressure to about 5lbs until the code is cleared.
First I checked all of the pressure side clamps on the turbos, the intercooler, throttle body, etc, then checked all of the hoses that go to the wastegates and wastegate actuator solenoid that is on top of the intake manifold. Nothing seemed loose, no holes or cracks in any hoses, etc. Problem persisted when towing.
As a couple of weeks went by I noticed in my daily driving that the truck was getting more and more "piggy", needing to rev higher in the RPMs to get up to speed, boost pressure not getting much over 15 at full throttle (it hits 20 with the tune), and really slow to build pressure in normal daily driving.
At this point I was thinking that it's either a faulty wastegate, wastegate actuator solenoid, or blow off valve (ford calls it a turbocharger intercooler valve). The two cheapest of those parts are the wastegate actuator solenoid ($28) and the blow off valve ($58). Now the blow off valve has a rubber diaphragm inside, which from what I found online can develop a tear, so that's the part I was hoping caused the problem, and if the tear were enlarging, that would explain why the problem seems to be getting worse. So I ordered part # AA5Z-9U465-A and upon removing the old one last night I could immediately see the tear in the rubber diaphragm. Bolted the new part in place, reconnected the electrical connector, took it for a test drive, and WOW is the power back!
Hope his helps someone save a lot of troubleshooting time and/or money.
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