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Thread: very poor gasmilage... where should i start?

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    Van Enthusiast joegri's Avatar
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    very poor gasmilage... where should i start?

    hi all let me start by saying my van has sat for many years maybe as many as 10 or so. ive been driving it everyday for 2 months and its comming along nicely now it just needs paint. after doing a gasmilage test my van is getting around 13 or so mpg. the exhaust doesnt have a terrible smell and it seems to have good power. i,m going to the parts store this morning for plugs and air filter but, if that doesnt do it i was wondering what to look for after that? what ever it is it must be corrected to get it over 17 mpg. i do town driving cuz it,s my work van and my customers are all close to me. i know this is a general question so i,m kinda looking for general ideas. thanx for any input.

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    Administrator llamavan's Avatar
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    Re: very poor gasmilage... where should i start?

    5-speed or automatic? And to verify, all the driving you did was in 2WD, you didn't use 4WD ... or did you?

    Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: very poor gasmilage... where should i start?

    Guessing can get VERY expensive.
    Start with checking for codes.
    If the engine is running well and the tailpipe isn't black/sooty and you have no stored codes, then look at things which will affect rolling resistance.
    Brakes dragging is a biggy, as is tire pressure and wheel alignment, bearings and the list goes on.
    Eliminate as many variables as possible before spending money on parts.
    There is no benefit in replacing parts that aren't required, besides you will need that cash for the things it really does need.
    -BB

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    Re: very poor gasmilage... where should i start?

    thanx for the quick responce llama and boot! the van is a 5 speed- it wasnt in 4wd -all brakes are adjusted pefect . and the air pressure is stable n good. i replaced the air filter and was looking for a mouse house in the air tube,that was nice n clean. i did find a that the plugs were not matching and put new ngk in. i dont know how to check the codes? but i have read in the past that alot of vanners do that. i just dont know how. but as i was looking for something that really stuck out the o2 sensor really looked beat!! just 1 rusty nut holding it on and the other completely gone and the gasket looked to be a mess too. i thought i saw somewhere o2 sensors on sale or should i say affordable. anyway i,m gonna bump around and try and find out how to check the codes.if i was a bettin man i,m leaning toward 02 sensor or egr valve? i guess i should update the picture in my avitar cuz she dont look like that anymore!!! thanx for yer input and maybe point me toward code checking.

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    Re: very poor gasmilage... where should i start?

    There is a yellow connector with a black rubber cap on it, located above the intake hose to the air filter assembly, the one you want is the 2 wire plug. Pull the rubber cap and install a jumper wire between the 2 terminals.
    Turn the ign switch on to the run position (do not start) and count the flashes of the check engine light.
    If there are no stored codes it will flash on/off/on/off till the cows come home. If there is a code(s) it will flash out a morse code,
    IIRC it will signal each code 3x before moving on to the next one.

    If the Oxy sensor looks toast, it probably is, sometimes they wont even store a code but still cause problems.
    You still want to check codes first, just to make sure there aren't other issues at play.

    If we are talking about the 88, it should have 2x O2 sensors, one in the front pipe, the other just behind the cat in the over-axle pipe.
    BB

  6. #6
    Administrator llamavan's Avatar
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    Re: very poor gasmilage... where should i start?

    Definitely a new O2 sensor! You may see a 1-2 mpg improvement after that.

    Go here to learn how to pull codes.

    Go here for all the codes.

    It pays to get acquainted with our TVT Library!!!

    Cleaning the throttle body can't hurt and may help.

    A damaged throttle position sensor is something else that can make the van run richer and get crummy gas mileage. The part of the TPS that keys the unit to the throttle itself is plastic, and under continued high heat (at which our vans excel), that plastic discolors and disintegrates, gradually causing greater and greater discrepancies between reality and what it "tells" the ECU. At first it's hard to tell there's a problem (especially with a 4WD van, which is more sluggish accelerating from a full stop to begin with), but there's increasingly poor response to the accelerator and later a discernible loss in power under load. In my experience, it has to be TERRIBLE before the van throws any codes. Many people are finding that their vans' TPS begins to fail in the 100-150K range (Trustyvan's original just started to croak with over 340K, but he's clearly the exception). So if the O2 sensor doesn't help substantially, that's where I'd check next since you've already done the air filter and plugs/wires, and also because it's only a matter of time before it will need to be replaced anyway.

    At least you have a 5-speed; that will help. Under the driving circumstances you outline, "good" fuel economy is relative. My experience is that I get the worst mpg (by far) in 4WD, but also a noticeable drop in mpg if I've had to stop and start more (not even necessarily a lot). So it's good your goal (17mpg+) isn't too high. FWIW, on the open road, my 4WD outdoes my best 2WD (stripped out) van ... not by much, but it does, and that again points up that the fuel economy penalties of 4WD show up in city-driving situation.

    ~ Gwen
    1985 5-speed window cargo van set up for llama haulin'; 345K ("Trustyvan")
    1989 4WD 5-speed DLX; 410K and an odd sense of humor ("Skylervan")

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    Re: very poor gasmilage... where should i start?

    Good advice from the previous posters. I wanted to weigh-in regarding the Oxygen sensor(s). New ones are relatively inexpensive and are well-worth changing-out after every 30K miles or so. They are a too often overlooked tune-up part that can make significant increases to your fuel economy.

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    Re: very poor gasmilage... where should i start?

    thank you so much for posting the "how to" info !!! i,ll have a lil time today to cypher what the heck is going on with my van. good stuff!

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    Re: very poor gasmilage... where should i start?

    that was cool news!! i went ahead and did a code check as described and it appears that all is well with the van. the only flashing that i got was a flash every 3 or so seconds, i believe that means no problem found? but im still gonna replace the o2 sensor. i though i,d post a pic of the ugliest o2 sensor on earth! also just a few pics of my van. Name:  brushcupbuild 027.jpg
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    Re: very poor gasmilage... where should i start?

    The Bosch oxygen sensor site at http://boschautoparts.com/Technical%..._Intervals.pdf has some good information regarding the checking and maintenance of oxygen (e.g., O2) sensors. The following is from the URL above:


    “Slow” PRE-OBII oxygen sensors will cause a drop in fuel economy of 10-15% (costing the average driver about
    $100 per year in extra fuel costs), while also causing excessive exhaust emissions (air pollution). Poor driveability
    (hesitating or surging) may also result in some cases.

    Additional technical and maintenance information on O2 sensors can be read at the following URL:

    http://boschautoparts.com/TechnicalR...Resources.aspx

    As many of you know, the vehicle computer typically reads five (5) or so sensors to calculate the air/fuel ratio. One of the main sensors is the oxygen sensor! The other main sensors are coolant temperature, throttle position, knock sensor, mass air flow (MAF) sensor. The MAF sensor can be easily cleaned using aerosol cleaners made specially for the MAF sensor and throttle body (parts of the air intake). Of course, cleaning the throttle body and the EGR passages should also be on your list of things to check and regularly clean. BG makes a product called K44 that effectively treats EGR and throttle body intakes. It is a powerful cleaner, yet safe for O2 sensors and throttle bodies (which have an internal coating so that carbon-based crud won't stick to its inside surface). For high-mileage engines, it is essential to clean the throttle body's inside surface and the throttle plate (these affect idling / rough idle conditions if dirty). Also, 3M has recently come out with a do-it-yourself kit (available at my local Autozone store for around $35) that has a nifty S-shaped plastic straw that threads inside immediately before your throttle body - 1/4-inch in front of it - to deliver a mist of powerful throttle body/throttle plate cleaner. This method is quite effective for cleaning the throttle body/throttle plate and may be helpful in getting into some of the EGR ports for cleaning them too. However, it is alsways best to remove the throttle body if practical to do so, to perform a very thorough cleaning of the surfaces and passageways of throttle body and EGR internals.

    I have seen 100K+ mileage engines that have had EGR ports totally plugged by carbon deposits (1/4-inch long plugs of hard carbon grit). These could only be cleaned by removing the throttle body and using a large hand-controlled drill bit followed by BG's K44 cleaner solution on a brass gun cleaning brush. the result was an as-new throttle body with unobstructed EGR ports.

    Gas mileage and performance drastically increased as a result of this two-hour maintenance routine.

    Note that I also use a "potassium nano-borate" (e.g. nano-particulate roach powder ) oil additive/friction reducer in my motor oil to yield increased fuel economy. I have seen gains of < 2MPG with this stuff. Read about this technology here:

    http://www.anl.gov/Media_Center/News/2007/ES070803.html

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    Re: very poor gasmilage... where should i start?

    MT has hit the nail, so to speak.
    Lack of codes doesn't mean all is well, just the first the first place to start.
    I failed emissions this summer, replacing the front sensor (which tested fine but was old) earned a pass (and a HUGE reduction in emissions)

    Having already been down the TPS road I wouldn't bother trying to clean anything, get a gasket and new tps, take it apart and follow Tim's guide.

    I had cleaned mine and felt I did a good job but once it was apart, I realized there are a lot of places that you just can't clean without disassembly.
    I also replaced the 2 coolant hoses (fed by the hose of death) while I was in there.

    Inspect and correct everything you see while you have it apart as it will never be easier than right now.

    Van looks great.

    I suspect those roof racks may impact your mileage to some degree.
    BB

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    Re: very poor gasmilage... where should i start?

    well i just got the results back (mileage check) after replacing the plugs and air filter and its up to a whopping 16 mpg! thats better than the 12 or so i was getting earlier this week. i ordered the o2 sensor and wont be here till sat or monday. also spied out the tps video and the how to remove the egr valve. so that will all be done when i have all the parts in hand and some ok weather!!i,m pretty confident that the van will be at peak performance after its all said and done. i was pondering the seafoam trick only cuz this van sat for many years (3 in the junkyard that i bought it from and 7 it sat in the backyard waiting to get it together).after all the new parts are installed i,m gonna take it up on the highway with some high test and go for a long ride... kinda see what that does.and thanx for all the help putting me in the right direction!!

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    Re: very poor gasmilage... where should i start?

    Just the kindof stuff I'm lookin for I want to be able to do this stuffmyself so I dont get stranded in the middle of the desert cause im too cheap to buy a 20dollar partand have a shop put it please postmore things for a new van owner to check/replace

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    Re: very poor gasmilage... where should i start?

    ok vanners just a quick up date . throttle body cleaned- egr valve cleaned- new tps installed and now this evening the o2 sensor installed. the ols o2 was so badly in the system(rusted) that the plan of attack was to cut the old out and just weld a new pipe in. the low fuel light just came on and if my math is correct i,m seeing 21 mpg around the town before the o2 was installed!!!!!! so it will get mo better. i can only say that if yer rigg aint gettin it (poor performance) go ahead n do these simple tricks. i was sooo scat to do this repaid but, with the help of you guys it was so easy. at the moment i,m a happy vanner. just go ahead n do it lots of help here.
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    Re: very poor gasmilage... where should i start?

    oppps my bad math. it,s more like 18 mpg. maybe this weekend i,ll take er up on the highway with some hi test and stretch the old van legs out!

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    Re: very poor gasmilage... where should i start?

    Where can I get a new tps/o2 sensor/egr valve.seems like newones would help to pass smog. Isthat a good place to start if I dont pass?

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    Re: very poor gasmilage... where should i start?

    If available your local Toyota dealer should be able to get them for MSRP. Some of the internet discount sites will save you up to 30% off of MSRP. I'm sure there's other's out there, but a couple of popular ones are www.1stToyotaParts.com and http://www.toyotapartszone.com. Tim

    PS: I wouldn't spend my money on a new EGR unless it tested bad.........then I'd probably find a good used one in the junk yard rather than pay Toyota's price. As for the o2 sensor, a good place to buy is www.sparkplugs.com. They sell different brands there, but if you purchase Denso you will end up with exactly the same thing Toyota would sell you...............but at a significant discount. Toyota's TPS runs about $75 or so, but I tried a Beck Arnley one I found on www.rockauto.com for under $20 (put it in one of my beater vans) and so far it's been doing fine..............although I have to admit I don't trust it or feel as good about it as I would a genuine Toyota TPS. Tim

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