2.3L ('83-'97) 96 Ranger 2.3L Constantly Switching from Open Loop to Closed Loop

[ksimp]

Hi All,

My 1996 Ford Ranger with a 2.3L, 5 speed is having issues running. Sometimes it will not idle without holding the pedal down to around 1500 - 2000 rpm. When it does idle, if you push the pedal it will go dead. I hooked up an Autel scan tool, and I noticed it was constantly switching from open loop/drive to closed loop, back to open loop/drive to closed loop, etc. The fuel pressure is good 35 - 40 psi (new fuel pump). MAF, IAC and TPS look good (checked with Autel while engine was, barely, running). I can smell unburnt gas while it is running. Engine is also loping while it is running. Please let me know if there is anything else I need to test.

Thank you very much for your help.

 

[franklin2]

Does your model have a fuel pressure regulator on the fuel rail? And it has a vacuum line going to it? Pull that vacuum line and see if it has fuel in it. I know the pressure is good, but I would still check it to make sure.

 

[ksimp]

Yes, it has a FPR. I replaced it about 4 months ago. I noticed the vacuum line was thin and stressed on the end connected to the FPR. So, I replaced it with a thicker vacuum line. There was no gas in the vacuum line.
Thanks

 

[franklin2]

Check it again to be triple dog sure. I do not trust new parts anymore.

 

[scotts90ranger]

There's several criteria it checks to go into closed loop, one is the signal from the O2 sensor, if it's old or original it would probably be worth changing.

Might be time to do a compression and possibly leak down test to check the general health of the engine, looking at the MAF reading is a reasonable thing to do but these things have a tendency of recessing valves...

 

[ksimp]

Thank you all for your replies.

I pulled the fuel regulator vacuum line to double check for gas leaking from the regulator valve. It was dry.
While working with the truck, I noticed the CEL did not come on when I turned on the key. It used to work. I'd replaced all the bulbs in the gauge cluster with LEDs, and it worked afterward. I back probed a test light to the actuator wire (pin #2 - pink w/ light green) on the PCM connector with the other end on the positive battery connector. The PCM was lighting up the test light as it would the CEL, if the CEL were working.

I've had the engine out for a rebuild, and the wiring harness that is behind the EGR pipe had gotten toasty crusty. I removed the outer cover(s), and some of the wires (some of them run to the PCM connector) were melted. I repaired those wires, but something tells me they may have rubbed through. Looks like I'll be pulling the upper intake again to have a look at those wires. If that's the problem, I'm going to need to find a better way to route the wiring harness after it's repaired.