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tech1229
tech1229, Auto Service Technician
Category: Car
Satisfied Customers: 5
Experience:  ase certs in auto repair and engine preformance - a/c and heating -brakes-electrical
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98 Ford Explorer Sport: V6..171,000 miles..check engine light..crank

Customer Question

I have a 98 Ford Explorer Sport V6. I have 171,000 miles on it. The check engine light has been on for over a year, it does not perform like it used to but it still responds well, I always am able to crank it right off. code scanner says it is getting error code P0420 - catalyst Efficiency Below threshold (Bank 1) and P0174 - System Too Lean (Bank 2). I cleared the code last year and got my inspection done and it passed the emissions test. I have not taken it for my new inspection yet. Any idea what it could be? bad intake manifold gasket? bad O2 sensor? bad cat converter?
Submitted: 11 years ago.
Category: Car
Expert:  tech1229 replied 11 years ago.
The computer in your vehicle uses an oxygen sensor in front of and behind each converter. The converter processes and reduces exhaust emissions. The computer program knows that there will be a difference in the information being reported from the front O2 sensor and the rear O2 sensor as the converter processes the exhaust emissions. As a converter ages it becomes less efficient. This loss of efficiency is known by the computer because of the information that the O2 sensors mounted before and after the converter report. Just because you have a converter efficiency code doesn’t always mean the converter needs to be replaced. A defective O2 sensor can cause this code to be set by the computer as well. Your technician has to check the O2 sensors to be sure that they are operating correctly and that other related systems are doing their job. If all checks good then a replacement converter is needed.
Customer: replied 11 years ago.
Reply to tech1229's Post: So their is no chance of it being the intake manifold gasket? I know if the cat converter starts to degrade the measurements of the two O2 sensor readings will get closer. Doesn't my vehicle have 4 O2 sensors? Will a Chilton book tell me what the voltages should be where I can measure them myself? I'm not knowledgeable about cars, but if I know what to do, I can get it dont myself.
Expert:  tech1229 replied 11 years ago.
if the trucks surges at idle or have high rpm idle you may have an intake leak, if not ,with that milage i would go with the codes.you can do it yourself check this site, about $198.00. they do reman. cats know.this is a good price. http://www.cheapexhaust.com o2s are about$45.00 here is a good price. https://www.automedicsupply.com there really isnt any way you can test the 02 yourself but with that milage you have, they more than likly are bad or at least weak. let me know if you need further assistance!Otherwise, I hope you have found this answer satsifactory and worth acceptance!

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