Just got a 2006 Ford Escape for $200, Trying to make it a daily driver for cheap

Well that’s a significant difference in readings, but a plugged exhaust that’s getting worse would also reduce your readings. Did you recheck the old MAF readings the same day as the new one?

Two diagnostics is recommend are 1: a vacuum gauge test and 2: watching the run engine in the dark.

The vacuum test should help point out the potential exhaust back pressure issue. If you could rent a back pressure gauge and tap into the o2 sensor that would be ideal…

The reason for viewing the engine in the dark is for watching for ignition system shorts. I’ve caught bad plug wires arcing this way before. Free and easy…

Don’t let this thing best you! Lol

About the engine in the dark, yeah check both when cold and when good and hot.
Had a 1970 Ford panel van with 6cyl. and it got down on power where you had to slam it into 2nd gear (3 on the Tree) to make medium steep grade hills.
Pulled the dog house one night and all the wires were glowing and arcing.
Next day replaced wires and ran like new engine, had to lower idle down even. Taught me to test for that on all cars since. Also have had a bad ignition wire when new, it does happen, so when people say well the wires are new OK but are they performing correctly.

Don’t think that is the problem here as his truck seems to go bad like someone is throwing a switch.
Where I live there are cheap Pull Your Own junkyards and I would be tempted to just go get the main computer if it is cheap enough and see what gives.
Had one take a crap on a Jeep, had lots of random electrical gremlins, replaced it and wala:)

Later

Sadly with a coil on plug setup you would not be able to see any of the high voltage ignition areas so that test would not help much I am afraid.

Indeed, it will run normally sometimes and then run bad again a second later like throwing a switch, which is why I am basically positive it is an electronics issue but nothing shows up on the OBD scanner.

The ECU is something I have considered a few times but the cheapest I have found one is $50+, that is a lot to waste on a longshot like that, particularly on a car only worth maybe $500 in it’s current condition.

Vacuum seems normal according to the OBD, it reads in absolute but gets down around ~3-4psi at idle which sounds about right.

I would recommend checking the vacuum with a manual/analog gauge, as the refresh rate often hides the more subtle behaviors.

I was going to suggest the same thing as Muto with going to a U-Pull-It for some random sensors etc…

Crank and cam pos sensors primarily.

BTW, does your OBD readout have a knock count? This is an issue that should surely trigger a DTC, but I am curious if it somehow its detecting knock and pulling timing/richening A:F

It did have a knock readout of some kind but it never triggered even when I could hear it pinging. I tested the knock sensor when the intake was off and it seems to be good, so this is another reason I suspect something deeper then a basic sensor error. That or the knock detection sucks on these ECU’s.

In my 4runner the knock detection is really good, you can get away with an amazing amount of abuse because of it lol.

I might toss a mechanical vacuum gauge on it and see what it reads, although so far everything has checked out as matching the OBD readout so loosing hope.

Going to try putting in my old spark plugs / coils today (have not been able to bum a ride to the parts store) to see if it shows any improvements, the plugs worked fine when I replaced them.

After this, sadly going to have to put it out to pasture for the time being so I can work on the 4runner, I am out of ideas for the Ford outside of the ECU itself.

Well, just swapped to the old coils and plugs, no change. I would of expected some kind of change if they were the issue.

The really strange part is that once again, it runs perfectly for the first few seconds after a cold start when still in open loop. Then it goes into closed loop and the issues start.

Pretty much rules out any mechanical, fuel, clogged exhaust or timing issue as those would effect open loop as well.

Just replaced the MAF. I could not find my vacuum gauge but the readings seem on point for the MAP sensor or at least close enough to not cause this big of an issue.

Anyone else have any bright ideas?

Only thing I can figure at this point would be the ECU itself but that is a lot to spend on a long shot. I have replaced the ECU in a few cars in the past with strange issues and it never worked before.

First few seconds you say… how many is that exactly? 5, 10, 30?

Hard to say exactly as I have not timed it, ~15 seconds or so I would guess today from a cold start. When it is already hot it is shorter.

I was watching the OBD at one point when it left open loop and the instant it did is when the issues started.

I have noticed this since I got it, just not as pronounced. When I would first start it up in the morning it would be really peppy and drive great until I was at the end of the block, by the time I took off from there it would be back to it’s old down on power ways.

Okay. Well let’s try and force it to stay in open loop for an experiment. Try disconnecting coolant temp sensor and see if that keeps it OL. If not, then disconnecting the upstream O2 sensor should. These will obviously cause a CEL but this can really point us in the right direction

EDIT: if it only took about 15 seconds from cold, then it’s likely the heated o2 sensor determining the switchover point. Coolant temp may not help

Interesting idea, I was wondering how I would go about forcing it into open loop but I worked with standalones or tuneable ECU’s for so long I never really learned what would cause a stock ECU to do that.

I will try the temp sensor first, assuming I can get at it. I remember disconnecting a plug next to the tstat when doing the intake manifold and not sure I can get to that plug with the manifold in place.

Oh. I forgot to ask what the load % reads now with the new MAF?

It was hard to get exact before/after numbers but it seemed to read a bit lower on average. It would still go to 100% with some throttle but seemed like it took a little more then before.

Hmm. So a minute of googling tells me there may be a fuse for the o2 heater circuit. That was on the v6, but the i4 may have that as well. That can be another way to disable/delay closed loop.

Cool, that sounds like the simplest option, I will see if I can find which one that is

Fuse #5. 15amp

Off to give that a try……

Well, sadly pulling that fuse did not keep it from going into closed loop.

I was looking for the temp sensor but could not seem to find it, did some searching and seems it uses a head temp sensor?

I have seen that plug by the coils but was not sure what it was for.

Shoot. Did you at least get DTCs ? P0141

Ok, disconnected the temp sensor in the head and tried again, still went into closed loop.

Although while driving I did notice something odd, when it gets up to the 4k RPM wall it would go into “open loop/deceleration”.

This is the same thing it says when I rev in neutral and the rev limiter kicks in at 4k.

Could it think it is in neutral?

Nope, no codes which I found strange as well, although maybe I didn’t leave it running long enough, I can check for pending codes next time I am out there.

Gonna let it cool off and try disconnecting the O2 sensor tomorrow most likely.