Trying to diagnose a loss of power on a 2008 expedition with 180k miles. Driving 70 mpg a week ago and it felt like someone tapped my brakes. Guessing roughly a 15-20% power loss but no CEL. So after reading up I replaced the IMRC and knock sensors while I was in there. No change at all except for a loss of $400. I've done a lot of work to this thing in the last two months. New timing set, oil pump, ford cams and phasers, plugs, cops, fuel filter, etc. Its been running fantastic the last 2500 miles since doing all that work. I don't think its an exhaust restriction. Both cats are the same temp so I dont think one collapsed. I thought for sure the IMRC would take care of it. And I'm still thinking its related to that. Whether it be a fuse to it or a broken wire somewhere. It was just like someone flipped a switch when I was going down the highway. I've been driving it a week and still no CEL so I have no other clues to go by. Considering getting Forscan to do some bidirectional testing but I'm also about ready to send it to a shop. The only other thing I can think of is the previous owner replaced one of the cam sensors with a knock off. Thinking about replacing that just to rule it out. But I also would think that would throw a code. Any help would be greatly appreciated. This thing has run like a scalded dog since doing all the engine work and I'm really frustrated to get it back to 100%.
08 sudden loss of power
- Thread starter 08TowPig
- Start date
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Guess I'll just keep a log for myself or anyone else who stumbles upon this later on. Not much going on in this forum...
Swapped MAF and cam sensors with known good ones and no change. Verified APP and TPS are functioning correctly. O2's and fuel trims look perfect. Both cats are the same temp via live data and are very close when checked with a thermal laser. So I dont think they're clogged or collapsed but cant say 100% without removing them or opening a hole up post cat. Waiting on my Forscan connector to come in so I can do some bidirectional commands. Really want to verify the IMRC is functioning as the wiring harness on the passenger side leading to the IMRC has been tampered with by the previous owner.
Swapped MAF and cam sensors with known good ones and no change. Verified APP and TPS are functioning correctly. O2's and fuel trims look perfect. Both cats are the same temp via live data and are very close when checked with a thermal laser. So I dont think they're clogged or collapsed but cant say 100% without removing them or opening a hole up post cat. Waiting on my Forscan connector to come in so I can do some bidirectional commands. Really want to verify the IMRC is functioning as the wiring harness on the passenger side leading to the IMRC has been tampered with by the previous owner.
And I also want to verify the cams are actuating like they're supposed to. Even though all the timing components are new, things can still happen. This engine had some metal debris from a seized roller follower that I had to flush out. Almost wondering if something broke lose and plugged up either the VCT solenoid or the manifold that it goes into.
whtbronco
Full Access Members
Not sure I can offer much at this point, but have you checked fuel pressure by chance?
FORScan should be able to help with the diagnosis as well.
It'll be interesting to see what you find ultimately.
FORScan should be able to help with the diagnosis as well.
It'll be interesting to see what you find ultimately.
Yes. Tested fuel pressure. 70psi at idle and 65 with the pedal to the mat in drive.
I just keep coming back to how it felt just like someone switched something off when I was going down the highway. Instant power loss.
I just keep coming back to how it felt just like someone switched something off when I was going down the highway. Instant power loss.
Pulled both downstream O2's and peered inside with a mirror. Both cats are intact at least in the middle section where the O2 resides. They are also operating with a 100+ degree differential between the inlet/outlet. So I'm 99% sure they're good. Starting to see like a APP, TPS or cam advancement issue. The APP and TPS seem to be closely following each other but maybe theres some other values that Forscan can offer when I get it up and running tomorrow.
These are before and after screenshots from replacing the accelerator pedal. I tried utilizing Forscan but it refused to connect. Any whos, the low power problem is fixed now. I have no real data to show what the problem was. Values D and E rose by 2% points. Apparently thats the difference. Hope this helps someone down the road. I intended to use the Forscan oscilloscope function to compare wave lengths but its a pretty useless program. Especially when it doesnt tell you “why” it wont connect.
