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On another forum I have been told that K & N air filter (the kind you clean with this special stuff instead of change like you do with the paper ones) is bad for my engine. What do you think? I am researching why my sudden loss of mpg.

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I'm not a big fan of K&N because they don't filter as well as a stock filters and I believe their gains are a good bit over rated. It's probably not causing your drop in mileage though if you are using one. You in Texas now? Wonder if there is a good independent Toyota shop near by?

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Yes, Southern Texas. Locals say there is a good mechanic in town and will check him out, I need a little muffler work also. Guess I will have him change out my air filter too. My CEL went on when my odometer rolled over to 100K and 3 mechanics have said not to worry about it, the code says oxygen sensor and I am wondering if I should get a new one, could that cause poor mpg?

I'm not a big fan of K&N because they don't filter as well as a stock filters and I believe their gains are a good bit over rated. It's probably not causing your drop in mileage though if you are using one. You in Texas now? Wonder if there is a good independent Toyota shop near by?

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O2 sensor will kill your mpg as well as cause a miss in the timing. I would replace the O2 sensor. I had a 22re fuel injected motor and used the stock filter and went to the K & N filter. There wasn't a noticable difference. So I would not waste any money on using K & N air filters or change to a header. 100K miles is nothing on these Toyota truck motors. The Japs made good motors and trannys. I would change oil and tranny fluid regularly. 3--4K on oil, and 20-25K on tranny fluid. Use NGK spark plugs which seem to be good too!

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I wouldn't go back to any of the 'mechanics' who told you not to worry about it. I'd say they would more correctly called 'grease monkeys'.

A K&N filter is not going to suddenly cause your fuel economy to drop. Drive it a bit with a new O2 sensor installed and try a quality paper filter if you like. See if it makes any difference. If not, you can swap the K&N back in when it's time.

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Yours may have 2 sensors so be sure they replace the right one and yes it will effect your fuel mileage the light is primarily for emission systems issues but if the emissions are out to lunch the engine is not running properly. Another tip, after market sensors are going to be a good bit cheaper and often made by Bosch (good quality) most parts supply houses will have them.

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Faulty O2 sensor could cause the engine to run rich (inject more fuel than is needed) as the ECU drops back to a default "Limp Home" version of fuel control.

I would start by looking at the O2 Sensor.

After you replace it, reset the ECU (pull the fuse or disconnect the battery for 60 seconds.

ALSO - double check for any coolant consumption. A leaky head gasket could dump antifreeze into a cylinder and the silica in the antifreeze could significantly shorten the life of an O2 sensor.

JOhn Mc

88 Dolphin 4 AUTO

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Agreed. If the mechanic looks the least bit confused about how to test or replace the O2 sensor, I'd either move on or get both replaced for peace of mind. In a properly equipped shop, it's an easy job. Undo connector, unscrew O2 sensor, install new one, reconnect connector. All that might be required is a special socket for an O2 sensor and perhaps a 'hot wrench' (oxy acetylene torch) to remove the old one, though the O2 sensor design might not even require the special socket.

I believe you have a V6 Toyota and they do have 2 O2 sensors, 1 before the catalytic converter, 1 after. This allows the engine computer to compare what the converter is doing.

Bosch and Denso are 2 well known names of suppliers.

http://www.autozone.com/autozone/parts/Bosch-Oxygen-Sensor/1991-Toyota-Pickup-2WD-6-cyl/_/N-itzhhZ9ixrp?counter=3&itemIdentifier=282411_0_5320_2425%2C4539%2C97999

http://www.autozone.com/autozone/parts/Bosch-Oxygen-Sensor/1991-Toyota-Pickup-2WD-6-cyl/_/N-itzhhZ9ixrp?counter=5&itemIdentifier=282414_0_5320_1382%2C4539%2C98000

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Ouch, sounds like I need a new O2 sensor (maybe two?) and a head gasket. I have been using a little antifreeze, I carry a gallon with me and add a little every few months or so, not a whole lot, a gallon lasts like 10K miles. Oil too, a quart every 5-6K miles.

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True story, I put a K&N on my Honda XR250R bike, this is an off road bike so it gets lots of dust. XR250's are air cooled 4 strokes called "bulletproof". I have been through the stock valves and two sets of "Black Diamond" stainless valves until I finally took the advice to toss the K&N. In all cases I used the K&N cleaning kit and filter oil religiously. In every case it was the intake valves that went, the last set sheared off at the valve stem doing $1800 damage. At the end I never could get the jetting right. The whole thing was that the filter was not passing enough air but letting through enough dirt. I had been down in some Mojave desert silt and it set up like concrete in the filter. I went back to a foam filter and have not had any valve recession since.

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Every thing you ever wanted to know about Toyota 02 sensors but were afraid to ask there is a short test at the end.

www.autoshop101.com/forms/h37.pdf (yours is not an OBD2)

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Cool, thanks. Although much of it is over my head. How do you know that mine is not an OBD2? And am I right that this means that mine only has one oxygen sensor?

Every thing you ever wanted to know about Toyota 02 sensors but were afraid to ask there is a short test at the end.

www.autoshop101.com/forms/h37.pdf (yours is not an OBD2)

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CA. had their own ideals on emission standards it is possible yours has 3 sensors but I don't think it does two O2 sensors and one air/fuel sensor. As Derek said OB2 did not come along until 1996 it is far superior then the older systems because it allows real time diagnostics and direct readings instead of blinking lights. A good shop should be able to fix you right up it's not rocket science.

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  • 2 weeks later...

OK my 7 cents opinion on K&N filters. I am presently running them in two vehicles. My Mazda B3000 V6 pickup and our 1990 V6 Toyota motorhome. After about 15000 miles I decided after looking at the out side of the filter in my Mazda ( a cone K&N filter) that it needed a cleaning. Considering what the outside looked like I was expecting the inside to not look so good. But to my surprise when I popped it off and took a look inside it was absolutely clean! I could not raise any residue with my finger or a rag on the inside or on the next component downstream (mas air flow sensor). I have attached some image of that cone filter for you all to see and come to your own conclusions.

As far as increasing horse power and gas mileage that's a mixed bag. I really do think it does both, but not in huge amounts where you are going to feel it in the seat of your pants and that wallet in the back pocket. I also used to run one on my turbo sunrader and it made a huge difference with the extra O2 the turbo wanted.

Anyhow you look at the pics and decide for yourself if it keeps the dirt out. The cone filter really increases engine intake noise to the point when you jump on it my B3000 V6 sounds like a muscle car. If it only performed that way. The filters are not cheap and you have to buy the recharge kit at some point but in my opinion they are OK.

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I’ve always liked the K&N filters. I used them on all my trucks and cars. I have not used one on my 89 Dolphin, but when the new engine is in, it will have one. I use the big cone filters too. I do know that you can oil too often and coat the air-flow sensor with a film of oil and then it will need to be cleaned. (I have a handy ultrasonic degreaser for that :-) In my 95 Tacoma work truck, I noticed a huge throttle response difference and the fuel mileage increased around 25-30 Kilometers more per tank. It sounds way better pulling stumps out too! :)

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Coolant consumption: a gallon every 10,000 miles is probably too much. Most Japanese engines in good condition should consume no coolant. Does this mean your head gasket is bad? Maybe, but not necessarily. You may also have a small leak in the radiator, water pump, heater core or a hose. Pressure testing the cooling system may turn up the leak. Some leaks are too small to pick up or only occur at a certain temperature. Another possbility is a radiator cap that is not holding enough pressure. This may cause boiling in the cooling system and you may lose coolant out of the overflow bottle as steam. A cap is cheap and easy enough to try.

I had disappearing coolant a few years ago on a 95 F150 4.9L six that drove me nuts. It needed coolant every few thousand miles, I could smell coolant but I could never find any leaking. Pressure testing turned up no problems. i was convinced it was a head gasket so I bought block tester from NAPA that checks for oil vapors in the coolant. None present. About 2 years later it finally starting dumping coolant on the ground when warm, but not cold or hot. That was enough to trace it to the radiator and replacing it solved the issue.

As a another example, the 1993 Civic in my signature is eating coolant. Has been for 60,000 miles. In this case it almost has to be the head gasket as I have oil in the coolant but no coolant in the oil.....which is backwards for a gas engine. Typically happens this way on a diesel.

You can try running oil and/or coolant analysis and look for the issue too. I use www.blackstone-labs.com and have for years. It's a good way to get an early warning on potential engine problems and learn if the oil you use is holding up once you have a base line.

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The best filter for your Toy is the oem Toyota filter. In my opinion K&N's do not stop a sufficient percentage of finer particles which will cause accelerated engine wear. Cotton as a membrane filter media is too weak and the openings between fibers in a K&N are far too large anyway. Pleated as in a K&N it is too thin to be effective as an inertial impaction filter. K&N is all about marketing and separating fools from their money.

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K&N filters are oiled we can get away with it in our Toyota's but if you use one on a hot wire MAF system it will kill the sensor. OEM filter hands down do a better job of filtering however the plumbing some times is quite restrictive and that is where K&N makes some gains. I personally will stick with a filter that maybe a bit more restrictive I would rather that then more dirt in my engine.

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Do our Toys have a MAF hot wire system? The Toyota Dealer installed a NAPA Gold air filter, is OEM a brand or a type? Did Toyota do me bad?

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OEM just means Original Equipment, meaning it comes out of a box with 'Toyota' printed on it. I doubt Toyota actually has a factory producing filters. The NAPA Gold they installed will do just fine.

Did they 'do you bad'? Depends how much they charged you for something you could buy at your local NAPA store and how much they charged for the 2 minutes needed to install it.

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Yes, saved the K&N, it looks dirty. They charged me about $50! That's a Dealership for you. They didn't say anything about the filter one way or another. Mostly I wanted to know if they put a poor quality filter. I am thinking the next line of inquiry should be, did the oil from the K&N get on my MAF filter?

I hope you kept the K&N filter so that you can return to using it (if you chose to) if you decide that the 'paper' filter doesn't cure your problems. Did the Dealership happen to make any comment about using the K&N?

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I wasn't sure what year your rig was so I searched a 1992 V-6. The NAPA Gold filter part number is FIL 2333 and has a suggested retail of $16.99. Many NAPA store are independently owned franchises so prices vary. Figure $20 on the filter so $30 for labor from a shop is not bad at all. Most shops have a minimum of a 1/2 hour labor charge and flat rates of $80-105 in Texas. I've only seen one shop (independent) with a flat rate lower than $80 in Texas. I think $50 out the door is a pretty good deal at a dealer. The NAPA Gold is their high line of filter. They have a Silver which is mid line and Pro Select which is the low line. Most of the Gold filters are made by Wix who is regarded as a quality manufacturer. I run Gold oil and air filters in most of my vehicles. They don't fit my TDI VW properly so I run the VW filter. Toyota brand filters are also high quality and can be ordered cheaply at www.1sttoyotaparts.com It may not make sense for just one filter though as shipping is $9.95 minimum.

Assuming your truck has a MAF (Mass Air Flow) sensor it could be fouled by the oil. There are some MAF cleaning sprays in aerosol cans that may clean it up. It's important to use the right cleaner as many can damage the sensor. Someone else will have to discuss where the sensor is and how to remove/test it. Most of my Toyotas have been carbureted so I"m not really qualified to help.

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Yes, saved the K&N, it looks dirty. They charged me about $50! That's a Dealership for you. They didn't say anything about the filter one way or another. Mostly I wanted to know if they put a poor quality filter. I am thinking the next line of inquiry should be, did the oil from the K&N get on my MAF filter?

Cris your's is no problem the hot wire systems are on much newer cars/trucks there is not enough oil in a K&N to bother your Toyota.

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Cris your's is no problem the hot wire systems are on much newer cars/trucks there is not enough oil in a K&N to bother your Toyota.

Does my 1991 have a MAF? If so, what cleaner should I get? Or are you saying that it should be fine?

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Does my 1991 have a MAF? If so, what cleaner should I get? Or are you saying that it should be fine?

Yours does have a air flow meter it's a bit different then a mass air flow sensor (MAF). No there is really no need to clean it.

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i donot know why people are knocking k/n filters-----------been using them on my 2000 gmc truck for 9 years -----1984 goldwing for 17 years----1999 chevy suburban for 4 years---and will not go back to paper filters as long as i am driving ---------just have not got arount to getting one for my 1990 toyota dolphin---but i am going to get one before i go camping again ----everyone has their opinion and i think they are worth the investment troyrobo

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5toyota says s ibelive kand n stock for use on webber 2 barrow carb have on 1978 20 r moter home not on 1988 4wd pu 22re 200oo miles on it

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