Question about Cars & Trucks
We located the mulfunction .its on o2 sensors but I am in doubt because I dont know which o2 sensor is bad downstream or up stream sensor
Oxygen sensors code sometimes produced because of some other problem, blocked exhaust or cat converter, over rice fuel supply or vacume leak in intake manifold giving a real lean mix and so o2 out of range in both casesw
Posted on Dec 10, 2012
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Posted on Jan 02, 2017
SOURCE: Upstream O2 sensor location?
That is the first sensor closest to the engine. The downstream sensor is the one behind the converter.
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Posted on Aug 31, 2008
Upstream, as in ahead of the converter, back toward engine. Start at converter and work your way back, should be on exhaust pipe or even on manifold.
Posted on Jan 11, 2009
the sensors before the catalytic converters are the upstream sensors, the ones after the after the catalytic converters are the down stream sensors, Ford calls them the Catalyst efficiency monitors.
Posted on Apr 26, 2009
In reading what you've already done, I would suggest a Compression Test along with a vacuum gauge hooked up to the intake manifold. It may be that you're burning oil through your exhaust system in the catalytic converter. I've seen this with leaking or inoperative turbo-chargers. Pull all of your spark plugs, marking them as to what cylinder they went in with a Sharpie and if worn, replace them. Check the distributor cap & rotor button for wear or cross-firing. A Haynes Manual for your vehicle is available through most part stores which is truly effective for your DIYer. Bad plug wires can send unburned gases down through both O2 Sensors and the Catalyst. You may also want to check the plug wires and the coil(s). A fast way of checking plug wires is to grab all of them with your hand with the vehicle running and if you get "zapped"...you need spark plug wires. Remember, the codes you pull are just a general starting point as to where to start your diagnostics, not the exact problem itself. The computer doesn't monitor the mechanical aspect of your engine nor the fuel supply. The computer will take this as a given, so don't forget that when testing that it could be a compression problem or fuel problem, but as I first said...an oil leak fouling your exhaust system such as an inoperative EGR valve or oil leak on the exhaust side of the valve train.
I hope this Helps,
Posted on Jul 18, 2010
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