Suggest to start by fixing the exhaust system so you are certain there are no leaks. Modern engines just don’t run well w/exhaust leaks. So not leaks of any kind, all the way from the engine to the tailpipe. Once that’s done, then next up, the intake manifold vacuum check for an exhaust restriction. I’d have the cat function checked too , best done by examining the pre-and post cat o2 sensor signals using Ford’s scan tool.
I’ve just watched this video recently:
Never though about such an “old school” method to check for restriction directly.
Went back today. He confirmed that the cats don’t get over about 400-450 degs even when it’s hot. I mentioned that it is like the gearbox shift totally skips Drive and that just doesn’t exist. After driving it himself, He suggested checking the shift cable and the drive bushings. He also said take a look at the fuel sensors.
Repulled the codes on his higher-end reader. Got 0135, 0155, 0402, 1406, 1131, 1132, 1152, 0171, 0174. He said replacing the exhaust manifold (leaking and has a couple of broken bolts) would likely fix 1131, 1132, 1152, 0171, and 0174. But not 0135 or 0155 (heater circuit faults for upstream O2 sensors) nor 0402 (DPFE - which I just replaced with an OEM 3 weeks ago - he said he has seen a lot of trouble with OEM DPFEs even right out of the box), and not 1406 (Faulty EGR sensor).
Considering my best next steps here, would you: work with the shift cables and/or bushings, the DPFE (return the one I bought and try again?), or the EGR sensor? Although, isn’t an EGR sensor just the DPFE, or is there a separate sensor for that that I’ve missed somewhere?
THANK YOU THANK YOU for the continuing discussion and advice and patience while I puzzle all this out. I have 7 kids and am due with baby 8 at the end of Sept- on top of that I work from home and really need to get this car running well and do as much of it on my own as I can.
Ask your shop if it is possible to completely disable the EGR system as a test. The Ford DPFE gadget is what fine tunes how much EGR to apply, and if it goes haywire you’ll likely get a very poor runner indeed. If you could narrow it down to the problem being too much EGR, then you’d have something to go on. p0171 and 0174 are both lean codes, and can be caused by too much EGR. As I mentioned before, the exhaust system has to be totally leak free on modern cars for them to run well, so if you still have exhaust leaks, fixing them is the number one priority imo.
I will ask them if this is possible. And continue to search for exhaust leaks. I do know there is the exhaust manifold leaking because of two broken bolts. That I just cannot replace right now, as much as I’d like to. But I have not found anyone yet who says that would cause the below 45 problem. The hunt continues! Thank you.
Exhaust leaks cause inaccurate readings at the O2 sensors, which can make the computer compensate by adding more fuel. this extra fuel, not being burned by the combustion process- will exit the engine and can clog up your catalytic converter or muffler- causing an exhaust restriction (which I agree with the others- this sounds most likely.)
If I were a DIY’er with limited tools and limited $$- I think my next step would be to disconnect/remove the exhaust before the cat/muffler and go for a ride and see if the performance improves. It will be loud, but I bet performance improves dramatically. This would point to an exhaust restriction.
(if you do this, do it safely, so not to be breathing in exhaust fumes. That can be deadly!)
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I agree, this is the most common DIY check for clogged cats. Unbolt it and romp around the block.
This is the biggest clue. Only excessive exhaust back pressure is going to blow the lines off the DPFE sensor. The EGR is designed to be closed at times and the lines won’t blow off the DPFE sensor then. And if you look at the pictorial schematic above, you can see how excessive back pressure can lead to false positive faults at the EGR as well.
Days of speculation. Back in the day, we just unbolted the cat and ran around the block. Today you may need to unbolt the exhaust further upstream but it can be done. Or spend the hour going to Autozone and buying a vacuum gauge. You have your answer in an hour tops.
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300 at rockauto. new manifolds are 45.
though there is also a center main cat for 275
so you might need 600 in cats for an entire setup?
?? In the diagram posted above, it looks like when the EGR valve is closed, that would allow a back pressure to build up more from a clogged cat, possibly blowing off the DPFE lines. When the valve is open then the exhaust pressure might be relieved a little through the path into the intake manifold. When the EGR is open though, like during accelerations, the exhaust pressure is probably higher than when it is closed.
The point I was making is the EGR is not responsible for lines blowing off the DPFE sensor so it is an unlikely root cause. It could be polluted now due to long term exposure to poor exhaust conditions but it’s not the root cause of the issue IMO.
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a new manifold is $60 delivered so i dont think that should be a price issue. unless your manifold bolts into the head are stripped/broken than removing the studs will be a challenge
They quoted me a lot higher - and there are two bolts they said will need to be drilled out, and they expect the rest of the bolts still in to break off as they go. 
I will see if I can unhook the cats this weekend and see how it runs.
You don’t need to remove the cats to check for an exhaust restriction.
Use a vacuum gauge.
Tester
The manifold vacuum idea is a pretty simple test, so try that first. If you get ambiguous results, another idea, sometimes its possible to remove just the pre-cat O2 sensor, and let that hole be the exhaust pipe bypassing the cat. For test and diagnostic purposes only of course. Given everything you’ve said, it does sort of seem like you have a clogged cat.
I did do that once and went out to see what would happen. We did not attempt to get on the freeway that way, but did at least get to about 50-55 mph on a main road. And it did run better.
The shop said that the temps for the cats were not going very high (not even over 500 degs) so he would not have started looking there but maybe I just need to bite the bullet and make that my next fix. I’ll try out checking the manifold vacuum test too
If I am throwing DPFE codes and EGR codes, and no Cat codes, but removing the O2 sensor does seem to help - would YOU go straight to cat replacement instead of tinkering more with the DPFE and EGR?
What you just described are the classic symptoms of a clogged exhaust
I think your cat(s) are clogged, but you’d best find out why
Some possibilities include ignition misfires, overheating, high engine oil consumption, and so on
This does seem to be the inevitable conclusion no matter which way I turn - whatever the pro shop says.
I imagine they are clogged at least partly because of the exhaust manifold leak, no? I’ll research on how to figure out the cause, but if you have any tips I’m definitely up for new ideas!
Quick update: I have no idea what happened but today there was a “pop” while of driving at about 15 mph (had just accelerated out of the store parking lot) and it was suddenly VERY loud. I think something else happened with the exhaust manifold (it was definitely from the engine and definitely from that general area) like maybe a final bolt broke loose or something. Either way once that happened I was almost afraid to drive it even the 2.5 miles to get home. So I am going to just have to see what I can do to have a shop fix it and hope that will make it a good running van to ferry about 10 people. I am about out of ideas on what more I can do myself. Thank you all again for being so generous with your time and knowledge.
A spark plug may have blown out, you shouldn’t be driving this vehicle with an exhaust restriction unless you plan on sending it to the scrap yard.