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Crazy Mileage drop, o2 sensor?

NickStorey

Member
Joined
August 19, 2013
Messages
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City, State
London, Ontario
Year, Model & Trim Level
2005 Explorer XLT, 4.6 V8
Hey, Im new to the forum, but I have been having some issues with my X.

Just got her about 3 weeks ago, 4.6 V8 '05. 150kms. I drove down to my hometown (about 1200km roundtrip) and parked for the night, took my parents truck to Detroit, when I returned the next day, and got in it and headed back home, I noticed my mileage went to the ****ter. I can (since then) basically see the needle going down as I drive. I have basically HALVED my mileage.

Some other details if anyone can help, Im getting desperate. As I started on the highway to head home that day my check engine light and gas cap light came on. went to partsource, got her scanned, only returned the fuel cap (which I replaced) and nothing else. had them turn off the light.

Since I have thrown in premium fuel, engine/fuel injector/etc cleaner, and the like, no luck.

basically I can only think from research that its my 02 sensors or spark plugs.

Any suggestions? I am desperate as I said....

Thanks!
 



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Take your foot out of it.
 






Since I have thrown in premium fuel, engine/fuel injector/etc cleaner, and the like, no luck.

basically I can only think from research that its my 02 sensors or spark plugs.

Any suggestions? I am desperate as I said....

Thanks!

Get the "fuel filter" changed for starters, then maybe a tune up. Old fuel filters can get clogged up with gunk which restricts the flow of fuel that goes thru them.
 






Along with taking your foot out of it, start with the fuel filter.
Check your tire pressures!
You should consider forgetting the premium fuel... Use regular octane.
Buy a can of seafoam and read the directions. It's good stuff.
Check and replace that air filter! Don't just blow it out.
Do an oil change to synthetic-use a synthetic filter.
Clean Mass airflow sensor and throttle body. Use only MAF sensor cleaner, or search the forums ( I think someone used vinegar )
Clean your IAC valve.
New motorcraft plugs, new motorcraft wires. Do one at a time so you don't cross the wires.
--- Don't go way too tight into that block when reinstalling plugs. :)
Replace coil pack with screaming demon coil pack-- or a motorcraft one.
Check your drive belt for cracks and wear while your in there.
Check your coolant level and clean your radiator with a hose if it is full of bugs.
Check battery and alternator for proper functionality.

Any questions, post here and also search can be very helpful.
 






Thanks for the speedy replies guys! And alot of good advice here!

So for starters I got a new K&N Air Filter, and cleaned the Air Metre with a special cleaner, I may have to try seafoam, I've heard good things!

Also I've been told to clean the 02 sensors but I don't know where the damn things are, someone said on the intake pipe, and others on exhaust, is this something I can do without hoisting her up?

Most other things I have done or will try out, also I bought new spark plugs just need to install them, is that very diffiult of a task?
Sorry I haven't done alot of work on cars before.

Thanks!
 






Thanks for the speedy replies guys! And alot of good advice here!

So for starters I got a new K&N Air Filter, and cleaned the Air Metre with a special cleaner, I may have to try seafoam, I've heard good things!

Also I've been told to clean the 02 sensors but I don't know where the damn things are,

also I bought new spark plugs just need to install them, is that very diffiult of a task?
Sorry I haven't done alot of work on cars before.

Thanks!

Don't expect to see any great difference in MPG'/KPG's with the K&N air filter, especially the "drop in" one. BY "Air Metre" do you mean "Mass Air Flow Sensor"?

Not positive on this, but I think the O2 sensors are screwed into the cat converters and there maybe 3 of them total in the exhaust piping. Read the Seafoam can label to see if it is suppose to help clean the O2 sensors when you dump the can into the fuel system aka gas tank. Whether it really does or not is anyone's guess.

Your spark plugs are the 'coil over" type for the V-8. Don't over tighten the plugs when installing them, the torque for your spark plugs is 156 inch lbs for the 2005 model V-8. Use die-electric grease with the plugs as well. Use a torque wrench when installing them and you can put a small dab of "anti-seize" compound on the plug threads. The link below should show you how to change out the coil over spark plugs.

http://www.explorerforum.com/forums/showthread.php?t=248208
 






Don't expect to see any great difference in MPG'/KPG's with the K&N air filter, especially the "drop in" one. BY "Air Metre" do you mean "Mass Air Flow Sensor"?

Yea I didnt expect a drop in to make that much of a difference.. unfortunatly.

As for Air Metre, from what I gathered it is the same, I googled the part number on it and thats what it seems to be.

the O2 sensors are screwed into the cat converters and there maybe 3 of them total in the exhaust piping. Read the Seafoam can label to see if it is suppose to help clean the O2 sensors when you dump the can into the fuel system aka gas tank. Whether it really does or not is anyone's guess.

But I have yet to use the Seafoam so I will look into that and get back to you. Does the Seafoam do the same thing cleaning them as it would removing the 02 sensors and using my cleaner and "manually" cleaning them?

That forum also looks like exactly what I need to do the spark plugs, Thanks!
 






Sea foam may clean the o2 sensors. Why not try injecting it into the brake booster line? See instructions on can for procedure. The brake booster line is connected to the master cylinder on the driver side firewall. Be careful removing the line. Make sure to reinstall properly and test brakes before you resume driving. I really don't think your o2 sensors are the issue so long a you are not throwing a code.
 






. Does the Seafoam do the same thing cleaning them as it would removing the 02 sensors and using my cleaner and "manually" cleaning them?

That forum also looks like exactly what I need to do the spark plugs, Thanks!

I would imagine cleaning an O2 sensor by hand would be a more thorough cleaning than just dumping some parts store fuel injector cleaner into the gas tank. I took my Explorer into a Ford dealerships 'Quick Lane" center 2+ years ago for a professional fuel injection cleaning. It cost $89+ tax and they hook up a large bottle of fuel injector cleaner (Brand of cleaner was -"Caster" I think? I'll check later today with the sticker in the engine bay) into the fuel line at the fuel rail and let the vehicle run off of the cleaner in the bottle, when that's done, they pour a can of cleaner into the fuel tank as well to treat the gas in the tank. A much more thorough cleaning. Cleans O2 sensors as well as injectors and fuel lines. Does not clean the "Throttle Body", that is a separate cleaning procedure. I did mine myself.
Better look more into any hand cleaning procedure first, before attempting it yourself. You don't want to damage the 02 sensors and wind up spending more money on new sensors.
No problem on the spark plug link, good luck! :thumbsup:
 






Easier and cheaper to change the fuel filter than the O2 sensors - do that first, and see how it goes. The 02+ explorers have 4 x O2 sensors at roughly $60 each, but only 1 fuel filter at roughly he same price. With 150k km on the clock, it's unlikely the filter has ever been changed, so now is as good a time as any.

For the record, the O2 sensors are in the exhaust - there is one before the first cat, and one after the first cat - repeated on each side for a total of 4. The 3rd cat doesn't actually do too much at all since the first 2 cats (one each side) actually kill off most of the noxious exhaust gasses.
 






First, after installing a K&N filter, you'll probably need to clean your MAFS again, as it is common for a freshly oiled/installed K&N to "bleed" excess oil off, and contaminate the wire on the MAFS. That will definitely effect MPG.

Second, forget trying to clean your O2 sensors. Half the battle is just getting them out, and its not uncommon for them to get damaged in the process. Its fairly easy to bend/tweak the end of the body while wrestling with a stuck on/rusty O2. Further, cleaning isn't really effective. Stop trying to cheap out, and just replace them.

If you're really tight for cash, just replace the 2 IN FRONT/UPSTREAM of the cats. These are the 2 that the ECM uses for controlling the A/F ratio. The rear / after cat o2 have ZERO effect on the operating parameters of the engine.

The ecm does NOT use the data from the rear o2's to determine or control A/F. The ONLY thing the rear O2's do is allow the ecm to monitor the efficiency of the cats. It compares the readings from the front o2's to the data from the rear. As long as there is a big enough difference, the ecm assumes the cats are working. If the readings are too close together, the ecm assumes the cat is not functioning correctly, and sets a code/check engine light. - AKA the infamous "catalyst efficiency" code (Its a P0402, I think). Some misinformed persons will argue till they're blue in the face, that the rear o2 sensor do effect how the computer controls the a/f ratio, but they are flat out wrong. Period.

Also, contrary to what some have posted, an O2 sensor can be worn out/"bad" to the point of having a significant effect on drive-ability and/or MPG, long before they have failed to the point of setting a code/check engine light. So, your o2's could be worn and need replacing, even without a light on. This is where a true "scanner" becomes much more useful then a cheesy simple code reader. You need to watch the actual real time values of the sensors, to see if they are "active" enough, and producing readings that make sense.

As far as your initial problem/question; there are any number of other things that could effect your MPG. Check for exhaust and/or intake leaks. Check all the other engine related sensors, such as ECT, IAT, TPS. Again, these could be returning bad data, while still not setting a check engine light. All can have a huge impact on MPG.
 






First, after installing a K&N filter, you'll probably need to clean your MAFS again, as it is common for a freshly oiled/installed K&N to "bleed" excess oil off, and contaminate the wire on the MAFS. That will definitely effect MPG.

Second, forget trying to clean your O2 sensors. Half the battle is just getting them out, and its not uncommon for them to get damaged in the process. Its fairly easy to bend/tweak the end of the body while wrestling with a stuck on/rusty O2. Further, cleaning isn't really effective. Stop trying to cheap out, and just replace them.

If you're really tight for cash, just replace the 2 IN FRONT/UPSTREAM of the cats. These are the 2 that the ECM uses for controlling the A/F ratio. The rear / after cat o2 have ZERO effect on the operating parameters of the engine.

The ecm does NOT use the data from the rear o2's to determine or control A/F. The ONLY thing the rear O2's do is allow the ecm to monitor the efficiency of the cats. It compares the readings from the front o2's to the data from the rear. As long as there is a big enough difference, the ecm assumes the cats are working. If the readings are too close together, the ecm assumes the cat is not functioning correctly, and sets a code/check engine light. - AKA the infamous "catalyst efficiency" code (Its a P0402, I think). Some misinformed persons will argue till they're blue in the face, that the rear o2 sensor do effect how the computer controls the a/f ratio, but they are flat out wrong. Period.

Also, contrary to what some have posted, an O2 sensor can be worn out/"bad" to the point of having a significant effect on drive-ability and/or MPG, long before they have failed to the point of setting a code/check engine light. So, your o2's could be worn and need replacing, even without a light on. This is where a true "scanner" becomes much more useful then a cheesy simple code reader. You need to watch the actual real time values of the sensors, to see if they are "active" enough, and producing readings that make sense.

As far as your initial problem/question; there are any number of other things that could effect your MPG. Check for exhaust and/or intake leaks. Check all the other engine related sensors, such as ECT, IAT, TPS. Again, these could be returning bad data, while still not setting a check engine light. All can have a huge impact on MPG.

Pretty good advice there^^^^

Rear O2 sensor codes are P420 and P430 (one for bank 1, one for bank 2) - I have recently had these as my cats were blocked/melted.
 






yea you guys make alot of good points, Im going to look into the fuel filter, as well as just replacing the 02 sensors, I only asked about cleaning them because a couple buddys said that would do it, Im not being cheap on not replacing them just didnt know that was the best route to go.

U did reclean the MAFS and I see a bit of an improvement. I will buy aome seafoam and try the master cylinder and let you know how that goes!
 






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