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Juan Crespo
Juan Crespo, Tech Trainer
Category: Car
Satisfied Customers: 1515
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Ford ranger 4.0L: I have a 1997 Ford Ranger 4.0L, Installed

Customer Question

I have a 1997 Ford Ranger 4.0L, Installed 3 new o2 sensors, new intake gasket set, checked for leaks. Have voltage to o2 heater circuit, but have trouble codes P0135, P0141, P0155, P1132, P1152. Bucks at low speed and 1500 rpm. Black tail pipe and running rich, any suggestions
Submitted: 1 year ago.
Category: Car
Expert:  Juan Crespo replied 1 year ago.
Hi there. welcome to our site. Those codes basically mean that there is a short to power on the sensor heater circuit and that the sensors are not switching. I've seen this kind of issue caused by previous work where wires have gotten pinched or have melted together, usually at the splice near the Octane Bar connector at the back of the engine. Please check there first and let me know what you find. Best Regards.
Customer: replied 1 year ago.
Had problem before any repairs, first replaced o2 sensors. Clean truck has original everything no previous mechanics have worked on truck. I will pull out the trans and o2 sensor harness tomorrow after it cools down and tear the wire harness apart and look for problems. From what I can see now the wiring is in every factory location and not been touched yet. But I will know more when I remove it.
Expert:  Juan Crespo replied 1 year ago.
Great. Please let me know what you find. Best Regards.
Customer: replied 1 year ago.
Pulled harness from engine, transmission and ecm. Went through with fine tooth comb and check each wire, nothing shorted or any other problems I could find. Tested each o2 sensor and they test good. Put everything back together and still same problem. Run ok until comes up to temp and starts running rough and blowing black smoke and get trouble codes. P1131, p1152. I am thinking an ecm issue. I even cut off fords battery cable ends and put new ends on battery cables. Crimp and solder and shrink wrap. Cleaned every ground on vehicles electrical harness. According to my scan tool. O2 voltage 0v. and fuel trim -100% . What do you think ever ran across this before
Expert:  Juan Crespo replied 1 year ago.
Thanks for the update.In my experience, P1132 and P1152 have been caused mostly by bad fuel pressure regulators allowing too much pressure, or in a few cases, by the PCM keeping the injectors open too long.For an accurate diagnosis, you would need to first check fuel pressure (tester available as a loaner from Advance, Autozone, etc.). If pressure regulator OK (fuel pressure 47-56 psi), then you would need a scan tool capable of reading engine data (PID) to check what the injector on-time is and , if excessive, determine why (MAF PID, ECT PID, etc.)Please let me know what you find.
Expert:  Juan Crespo replied 1 year ago.
Hi again. Just checking to see if the information I provided helped you solve your issue. If it did, then kindly accept and rate my answer now. If it didn't, please reply so we can keep working.Best Regards.
Customer: replied 1 year ago.
fuel pressure is 37 psi and 48 with vacuum off regulator. Fixing this issue. If I unplug mass air flow sensor engine smoothes out and no o2 codes. I don't believe that it is mass air flow sensor that is bad, but instead going into a fail safe mode. Got behind on other customers and have not had time to get back to the ranger. If you have any other ideas that might help me let me know.
Expert:  Juan Crespo replied 1 year ago.
Unless you have the returnless fuel supply system, 37 and 48 psi pressures are within specs. Unplugging the MAF sensor doesn't tell us anything related to our issue. What we need to find out is what the engine data is coming in and how the PCM is responding to that data.

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