car still has a cold start problem, and when its warmed up it now has a lope and sounds rich, whats next?

Asked by Jan 07, 2013 at 01:24 PM about the 1999 Ford Crown Victoria 4 Dr STD Sedan

Question type: Maintenance & Repair

we changed the 02 sensor, bank one sensor two. we changed the MAF sensor. we checked for vacuum leaks. we went to O'reileys to read the codes and got four codes prior to replacing the MAF sensor. they were P0136, P0300, P1131, P1151. we are going to O'reileys again to clear and reset the computer then wait for new codes to be read. the 02 sensor helped slightly, as did the MAF sensor

3 Answers

3,460

Downstream oxygen sensors do not effect driveability in any way. The upstream (before the catalytic converters) sensors greatly influence air/fuel ratio, spark timing, etc. Theres a well known issue with Ford MAF sensors that leads to bad oxygen sensors. You already changed the MAF, so dont worry about that. Just remember to give it a shot of MAF sensor cleaner (NOT brake parts cleaner) whenever you change the oil to keep it clean. Now you have to go change the upstream oxygen sensors and that should solve the issue. Remember to not only clear the codes, but also disconnect the battery to reset your fuel trim tables in the computer. Then drive the car for a few days to confirm all issues are resolved.

1 of 1 people found this helpful.
3,460

Also, check your sparks plugs, as having a misfire can foul out plugs fairly quickly.

8,605

You have 2 upstream O2 sensors, and only doing one will confuse the computer. Also, make sure to use the correct ones. There is a calibration code for the car, and that determines which sensors you need.

2 of 2 people found this helpful.

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