O2 problems

[Marlinmahi]

94 4.0 2wd auto. My truck smells of fuel from exhaust so I replaced the o2 sensors and sprayed out the maf sensor. Now I get an intermittent check engine light where I had none before. So I got a code reader from Amazon. The codes are: 111 10 175 176 181 and 189 with the engine off.
Running they are 136 538 and 536. Like I said the o2s are new. what now? Oh and I found the wire in the picture having down by the starter. Any ideas where it goes?View attachment 63392

 

[RonD]

I assume you unplugged battery for more than 5min when changing O2 sensors, so computer would clear all previous codes, if not then do that now, then drive it until its warmed up and CEL comes back on.
If no CEL then after its fully warmed up shut it off and check does again

I also assume you looked up the codes?

No one has them all memorized, lol
These 2 don't matter, they are tests you needed to do when in "test mode", brake and throttle
536 (O,R,M) Brake On Off open or shorted to ground - BOO
538 (R) System did not receive "goose" test - TESTS

111 System checks OK
136 (R) Oxygen sensor not switching/system lean Left or Front HO2S - Fuel control

175 (M) Oxygen sensor not switching - system was at adaptive limits - Left or Front HO2S - Fuel control
176 (M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control

181 (M) Fuel system was lean at part throttle Single, Right or Rear HO2S - Fuel control
189 (M) Fuel system was lean at part throttle - Left or Front HO2S - Fuel control

Left is drivers side
So it reads like you have an exhaust leak on drivers side exhaust manifold, or O2 is unplugged, or O2 is not screwed in all the way

Could be lower intake manifold air leak but should have higher idle which you don't mention

Are there and running issues?
Or just the smell of gasoline?

1994 computer may need the 3 capacitors changed, not hard to do, had to do my 1994's last year because of odd running issues, there is not set faults for bad Caps, just issues that can't be explained after changing other parts

 

[Marlinmahi]

The battery was disconnected.
How do I check the capacitors? I checked the wires to the 02s they are plugged in. I didn't have a cel before I changed them. The engines doesn't run that great. Bit of a miss and sluggish at times. Sometimes it boggs. I bought it about 2 months ago and had it in the shop for the transmission for half of that so I've just started driving it. Gets really bad gas mileage. Like 12mpg.
Why would it be throwing codes now for the 02s and not before. If I had a manifold leak wouldn't it have thrown a code before I changed the 02s?

 

[RonD]

O2s are the only sensor that always wear out, they run out of the chemicals to detect Oxygen
As they run out they give computer a FALSE lean, so computer adds more fuel, MPG drops, and NO CODES, because computer "trusts" O2 to be working, it has nothing to compare it to
O2s should be changed every 100k miles or 12 years

Why are you getting codes now?
Because O2s are working now I assume

I would plan on just changing the 3 capacitors as general maintenance at 27 years old
You need to pull out the computer and open it up
Leak cap looks like this: https://www.f150forum.com/attachments/f10/52991d1314063739-help-1991-5-8-2wd-engine-stumble-die-ignition-cutting-out-eec-diode-cu2.2.jpg
And this: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRC1n22K83PmFqQkWQu6VfXTNpnOO80rWvMdg&usqp=CAU

You need a soldering iron, solder and a solder "sucker", capacitor data is on the capacitors, under $5 in parts

Also look at the circuit board in general for signs of corrosion

I assume engine was running poorly before the new O2s or you would not have changed them, so it could have been a computer issue before and now

Also one more thing to check, on the 4.0l below/behind alternator on lower intake is the Fuel Pressure Regulator(FPR), it has the Return Fuel line connected to it, AND a vacuum hose, pull off this vacuum hose and check it for gasoline
If gasoline is found then that's whats causing some of the fuel smell and low MPG, replace FPR

 

[Marlinmahi]

Ok, thanks have ordered the capacitors and a soldering kit.

 

[Marlinmahi]

Just pulled out the ecm. Want to have a new one ready if I botch the old one soldering the capacitors. But when I go to rock auto I don't see a match. Here are the pics I took. I got an old flip phone so they aren't that great. Can someone please tell me which ecm on rock auto is the right one? I typed em9084s and google showed ecms with that number, one at rockauto. But when I looked at it, it said nothing about being for my 94 ranger and looking under 94 ranger 4.0 em9084 doesnt even show up.. Also I'm pretty sure the paper sticker says 2008. And the capacitors have scratches under them. Somebody's been in here before.

 

[RonD]

It looks like that's a rebuilt computer, Caps were Blue in the original, usually, and never seen the "red" on the top of each

Do they look OK, can't tell from pictures?

Are both wires still connected, move cap with finger to tell
They corrode on the under side and wire breaks

So it may be OK, the black ones cost more but last longer

 

[Marlinmahi]

One looks like it has a corroded soldering point. The other 2 look fine. Id like to just get another computer. How can I figure out which ecm to get. This just might not be the correct ecm.

 

[RonD]

You need an EEC-IV, 1993 or 1994, for a 4.0l engine size and Automatic trans
(1995 and up Rangers used EEC-V, so would work in 1994 or older)

2WD or 4x4 don't matter

If it has an EGR valve, which is unlikely in Florida, then you need a Calif. approved computer

It should have a part number that starts with F37F = 1993 Ranger, or F47F = 1994 Ranger

Then 12A650 = ANY COMPUTER in a Ford vehicle, Mustang, Fusion, ect........all have 12A650 to this day

So 1994 would be F47F-12A650-???

The ??? was Fords code for engine size and transmission type, and Ford never released a cross reference
And they use several different ??? every year for same engine/trans combo, so there is not one set code for 4.0l automatic

So F47F-12A650 part number can be for a 1994 Ranger with 2.3l, 3.0l, or 4.0l engine and either a manual or automatic

So best you can do is ask what a computer came from, engine size and transmission type

 

[Marlinmahi]

Its those last three letters in the part number I can't figure out. The ecm I have doesn't even have a f47f pt number.

 

[RonD]

Yes, you are going to be able to use any of the numbers on your current computer as its not original, so rebuilder could have used any chassis from any Ford EEC-IV

You want an F47F-12A650 for a 4.0l engine and automatic transmission

 

[Marlinmahi]

Why are there 3 different letters after the pt number many for a 4.0 2wd fed regs

 

[RonD]

You would need to ask Ford
On "regular" parts the last 1 to 3 number/letters are Revisions, AA would be first part, AB would be same part but updated slightly, then AC........ect..............
BUT.........they also used those as designation for included firmware, i.e. GEM module for no power window/door lock might end with AC, but if it had power group it ends in AE

The PCMs, computers, will be like that, ending A7E might be for 2.3l with manual, T1F might also be for a 2.3l manual
And that's just for 1 model year, A7E might be for a 4.0l Automatic the following year


There are all sorts of oddball stuff that must have made sense to Ford at the time, and still, lol
I am sure its all in a book somewhere but I have never seen it

 

[Marlinmahi]

Called ford gave them my vin. They gave me the ecm part number F47z-12a650-cla
Then they told me that part was obsolete. So I Googled it and found alot of places saying they had it but when you went to thier website it was either out of stock or discontinued. But I found a site that cross checked ecm's and it said F47F-12a650-cla would work. So I bought that one from rock auto for 171 bucks.
I'm wondering why the same company charges a different amount for the same ecm with a different part number. If they all work on the same truck.
Oh on the way home today the check oil light came on. Wtf its got plenty of oil. Monday's
Oh thanks for the info Ron,

 

[Dirtman]

Depends largely on the type of ECM you buy. An NOS Ford unit will cost more than a refurbished unit even though they are the same part.