- Joined
- Sep 7, 2007
- Messages
- 44
- Reaction score
- 6
- Points
- 8
- Age
- 42
- Location
- Denver, NC
- Vehicle Year
- 1996
- Make / Model
- Ford
- Engine Type
- 4.0 V6
- Transmission
- Automatic
- 2WD / 4WD
- 4WD
- Tire Size
- 31
I haven't shown my face around here for something like 10 years because I just got burnt out on forums. I've still got the same 1994 Ranger with a 4.0 in it and it now has 403,000 miles and counting. I've got some issues with it that for the life of me I cannot figure out and I'd rather fix this truck then buy a new one. I'll warn you, this is going to get long.
So about a year ago my lower intake gaskets started to leak a little water out the front so I pulled them off and replaced them. Shortly after that I started to get some issues with the idle. It would hang or idle high but fuel mileage never went down and power never changed. I figured I messed a gasket up and had a vacuum leak somewhere. I searched and searched and searched but never found the leak. I eventually just pulled the intake back off, inspected all the gaskets and found no evidence of any leaking and put it back together with new gaskets…same result.
I kept driving it but eventually it started stumbling and power was off. Soon check engine lights followed. I started getting a lean code on bank 2 and the matching O2 sensor wasn’t switching. I replaced the O2s thinking that might be the issue but it changed nothing. Same codes, same issues. I found that if you floored it and held it, eventually it would run correctly after stumbling for a bit and it stay running correctly as long as you were in the throttle hard.
I went rounds and rounds with some different codes but none of them were consistent. I thought I might have a leaking exhaust valve and since I have access to a machine shop I pulled the heads and completely rebuilt them. When I pulled the heads I noticed that bank 2 did in fact look like it had been running lean. After putting them back the same problem showed up.
The O2 sensor isn’t switching because that bank is in fact running lean. This is when I noticed on a data stream while driving that the fuel trim from that bank was about half of the other side. When you stayed in the throttle hard and it started to run correctly then the trim levels nearly matched.
Here is a list of what I have changed or verified against a known good part.
ECM – reman unit – did this after finding some leaking diodes and corrosion on my original ECM
O2 Sensors
TPS
MAF
Coolant Temp Sensor
IAT
Coil Pack
Fuel Pump
Fuel Pressure/Regulator
Fuel Filter
Injectors were cleaned and tested
Cat is not clogged
Keep in mind this is a 94, Federal Emissions truck so it does not have a cam position sensor or and EGR.
I’ve ohmed out injector harness and checked the grounds through the wiring harness going to the ECM and it all checks good. I’ve also verified signals going to and from all the sensors.
That’s a quick recap of what I remember from the past 8 months or so. I don’t work on it regularly as it’s not my daily driver anymore so it’s not as important. Now when I drive it I get no KOER codes but I get 3 KOEO codes and they make no sense to me. 177, 542 and 556
DTC 177
Lack of heated oxygen sensor switches, indicates rich (bank #2)
DTC 542
Fuel pump secondary circuit failure.
DTC 556
Fuel pump relay primary circuit failure.
Keep in mind that this is the first time this thing has ever thrown a rich code during this whole thing. Also, if the fuel pump circuit is failing then why is the pump still working? I took the bed off, cleaned the top of the pump, the terminals and checked voltage going to the pump and found no issue. Driving around with a fuel pressure gauge hooked up I have never once seen low fuel pressure.
Anyone have any idea what might be going on here?
So about a year ago my lower intake gaskets started to leak a little water out the front so I pulled them off and replaced them. Shortly after that I started to get some issues with the idle. It would hang or idle high but fuel mileage never went down and power never changed. I figured I messed a gasket up and had a vacuum leak somewhere. I searched and searched and searched but never found the leak. I eventually just pulled the intake back off, inspected all the gaskets and found no evidence of any leaking and put it back together with new gaskets…same result.
I kept driving it but eventually it started stumbling and power was off. Soon check engine lights followed. I started getting a lean code on bank 2 and the matching O2 sensor wasn’t switching. I replaced the O2s thinking that might be the issue but it changed nothing. Same codes, same issues. I found that if you floored it and held it, eventually it would run correctly after stumbling for a bit and it stay running correctly as long as you were in the throttle hard.
I went rounds and rounds with some different codes but none of them were consistent. I thought I might have a leaking exhaust valve and since I have access to a machine shop I pulled the heads and completely rebuilt them. When I pulled the heads I noticed that bank 2 did in fact look like it had been running lean. After putting them back the same problem showed up.
The O2 sensor isn’t switching because that bank is in fact running lean. This is when I noticed on a data stream while driving that the fuel trim from that bank was about half of the other side. When you stayed in the throttle hard and it started to run correctly then the trim levels nearly matched.
Here is a list of what I have changed or verified against a known good part.
ECM – reman unit – did this after finding some leaking diodes and corrosion on my original ECM
O2 Sensors
TPS
MAF
Coolant Temp Sensor
IAT
Coil Pack
Fuel Pump
Fuel Pressure/Regulator
Fuel Filter
Injectors were cleaned and tested
Cat is not clogged
Keep in mind this is a 94, Federal Emissions truck so it does not have a cam position sensor or and EGR.
I’ve ohmed out injector harness and checked the grounds through the wiring harness going to the ECM and it all checks good. I’ve also verified signals going to and from all the sensors.
That’s a quick recap of what I remember from the past 8 months or so. I don’t work on it regularly as it’s not my daily driver anymore so it’s not as important. Now when I drive it I get no KOER codes but I get 3 KOEO codes and they make no sense to me. 177, 542 and 556
DTC 177
Lack of heated oxygen sensor switches, indicates rich (bank #2)
DTC 542
Fuel pump secondary circuit failure.
DTC 556
Fuel pump relay primary circuit failure.
Keep in mind that this is the first time this thing has ever thrown a rich code during this whole thing. Also, if the fuel pump circuit is failing then why is the pump still working? I took the bed off, cleaned the top of the pump, the terminals and checked voltage going to the pump and found no issue. Driving around with a fuel pressure gauge hooked up I have never once seen low fuel pressure.
Anyone have any idea what might be going on here?
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