- Joined
- Apr 7, 2026
- Messages
- 1
- Points
- 1
- City
- Baton Rouge
- State - Country
- LA - USA
- Vehicle Year
- 1994
- Vehicle
- Ford Ranger
- Drive
- 2WD
- Engine
- 3.0 V6
- Transmission
- Manual
- Total Lift
- 2"
- Tire Size
- 31x10.50R15
I'm not even sure where to start here.
My 1994 Ranger STX (currently 4x2, but planning to [finally] SAS it later this year) with 3.0/M5OD started getting super weak a few years ago. I really don't drive it very often, but I really do love this damn thing and refuse to give up on it for sentimental reasons.
I've built Crown Vic station wagons in the past, 5.0HO and T5 swapped them, so I'm familiar with the EEC-IV system, but I'm far from a pro. I have an off road shop, so I'm usually more focused on suspension, tires, armor, etc.
Sorry- anyway... quick backstory: in December 2024 I replaced the fuel injectors on the Ranger and did a full tune-up... it has had a misfire since I acquired it in 2005, but it was running a bit more rough (and significantly slower) than usual at the time. In mid-2023 I installed all new A/C components and I replaced the entire ignition system, including the distributor, hoping that would clear up the misfire, but it didn't work. From there, I was hoping that a set of new injectors (I was still running the originals from 1994 after countless periods of sitting for months on end), a quick tune-up, and valve cover gaskets would have my kid set up to drive it for a few months in a pinch... but once I cranked it with the new parts, it ran 5x worse than before. I do think the new injectors simply amplified whatever was happening before that, but it's hard to say. I ran a compression test and thought #6 was super low, but that turned out to be a bad test.
It has sat at my shop since, until a couple weeks ago I decided to clean it up and start digging into it again. After an extended thrash session last weekend, I made some electrical progress when I discovered that the RABS module has failed and appears to be shorting to ground. That is currently disconnected until I can get a new module.
As far as the testing I've done...
All six injectors are firing (we did find one that was testing fine on the bench, but not installed, so we replaced that one) correctly.
All six spark plugs are firing correctly.
Timing is set (I can't remember exact advance without the pill, but it was standard- maybe 8-10*?)
Fuel pressure is 32psi (I know that's on the low end of the spectrum, but it still shouldn't run this ridiculously rich)
The (new Motorcraft) ECT is receiving 0.21v on the 5v circuit. There is no resistance on the wires from the sensor connector to the ECM connector.
The ACT is receiving 0.21v on the 5v circuit. There is no resistance on the wires from the sensor connector to the ECM connector.
The TPS is receiving 5.02v on the 5v circuit, but only sends a max of 2.9v back to the ECM at WOT. There is no resistance on the wires from the sensor connector to the ECM connector.
The MAF, when checking the ground into the ECM, is only able to carry 0.21v on that wire (that's with DVM + on battery + and DVM - on the signal return wire to test its ability to ground to ECM) There is no resistance on the wire from the sensor connector to the ECM connector.
The O2 sensors have no resistance on the wires to the ECM, no resistance to the grey/red combined signal wire, and elements pass resistance tests.
I checked the (I see 4) ECM grounds from the connector to the ground locations and all show zero resistance.
I removed, thoroughly cleaned, and re-installed the following harness ground locations:
Left fender (two between the starter solenoid and the ECM)
One at the radiator support near battery
One in the right kick panel
One in the left kick panel
I added 6ga (welding wire) grounds from the block to the cab (firewall), the block to the frame (original location), the frame to the cab (at the radiator support w/ the battery and harness grounds)
I'm not currently showing any sort of grounding issues anywhere, despite that everything I know about EEC-IV is telling me this is most likely a ground issue.
I got to the point I had decided it needed a new ECM, so I ordered one... and it's doing the same thing (not that anyone is surprised.)
I'm frustrated. I'm exhausted. I'm losing shop time because I keep trying to check one more thing. Does ANYONE have ANYTHING else to contribute as a possibility to test? I checked with all my old Ford tech buddies and no one has a breakout box I can borrow to make things easier, either.
My 1994 Ranger STX (currently 4x2, but planning to [finally] SAS it later this year) with 3.0/M5OD started getting super weak a few years ago. I really don't drive it very often, but I really do love this damn thing and refuse to give up on it for sentimental reasons.
I've built Crown Vic station wagons in the past, 5.0HO and T5 swapped them, so I'm familiar with the EEC-IV system, but I'm far from a pro. I have an off road shop, so I'm usually more focused on suspension, tires, armor, etc.
Sorry- anyway... quick backstory: in December 2024 I replaced the fuel injectors on the Ranger and did a full tune-up... it has had a misfire since I acquired it in 2005, but it was running a bit more rough (and significantly slower) than usual at the time. In mid-2023 I installed all new A/C components and I replaced the entire ignition system, including the distributor, hoping that would clear up the misfire, but it didn't work. From there, I was hoping that a set of new injectors (I was still running the originals from 1994 after countless periods of sitting for months on end), a quick tune-up, and valve cover gaskets would have my kid set up to drive it for a few months in a pinch... but once I cranked it with the new parts, it ran 5x worse than before. I do think the new injectors simply amplified whatever was happening before that, but it's hard to say. I ran a compression test and thought #6 was super low, but that turned out to be a bad test.
It has sat at my shop since, until a couple weeks ago I decided to clean it up and start digging into it again. After an extended thrash session last weekend, I made some electrical progress when I discovered that the RABS module has failed and appears to be shorting to ground. That is currently disconnected until I can get a new module.
As far as the testing I've done...
All six injectors are firing (we did find one that was testing fine on the bench, but not installed, so we replaced that one) correctly.
All six spark plugs are firing correctly.
Timing is set (I can't remember exact advance without the pill, but it was standard- maybe 8-10*?)
Fuel pressure is 32psi (I know that's on the low end of the spectrum, but it still shouldn't run this ridiculously rich)
The (new Motorcraft) ECT is receiving 0.21v on the 5v circuit. There is no resistance on the wires from the sensor connector to the ECM connector.
The ACT is receiving 0.21v on the 5v circuit. There is no resistance on the wires from the sensor connector to the ECM connector.
The TPS is receiving 5.02v on the 5v circuit, but only sends a max of 2.9v back to the ECM at WOT. There is no resistance on the wires from the sensor connector to the ECM connector.
The MAF, when checking the ground into the ECM, is only able to carry 0.21v on that wire (that's with DVM + on battery + and DVM - on the signal return wire to test its ability to ground to ECM) There is no resistance on the wire from the sensor connector to the ECM connector.
The O2 sensors have no resistance on the wires to the ECM, no resistance to the grey/red combined signal wire, and elements pass resistance tests.
I checked the (I see 4) ECM grounds from the connector to the ground locations and all show zero resistance.
I removed, thoroughly cleaned, and re-installed the following harness ground locations:
Left fender (two between the starter solenoid and the ECM)
One at the radiator support near battery
One in the right kick panel
One in the left kick panel
I added 6ga (welding wire) grounds from the block to the cab (firewall), the block to the frame (original location), the frame to the cab (at the radiator support w/ the battery and harness grounds)
I'm not currently showing any sort of grounding issues anywhere, despite that everything I know about EEC-IV is telling me this is most likely a ground issue.
I got to the point I had decided it needed a new ECM, so I ordered one... and it's doing the same thing (not that anyone is surprised.)
I'm frustrated. I'm exhausted. I'm losing shop time because I keep trying to check one more thing. Does ANYONE have ANYTHING else to contribute as a possibility to test? I checked with all my old Ford tech buddies and no one has a breakout box I can borrow to make things easier, either.
