Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Super bad mileage (and failing inspection)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BillyBob, Jul 6, 2001.

  1. BillyBob

    BillyBob 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    557
    Likes Received:
    1
    Location:
    Dumont, NJ
    Okay, before everyone says something like "you got a truck, who cares about mileage" and yadda yadda, I feel my truck is getting way below the "norm" on milage.. in the past week I've spent about $40 in gas (1.59 and 1.69/ gal) and travled a little over 100 miles. I've been tracking the milage since I wanted to make sure it was a good idea to switch from my 87 to my 84 K-5. Anyway, my 87 w/ 33" tires and 3.73s got around 12-15 MPG, which is really good for a truck. My bone stock 84 is getting around 7MPG if it's lucky. What the frick is going on? My friend keeps saying it's the Q-jet and exaust and that it's a carb and it's supposed to eat gas like a pig. But I highly disagree.I mean, the thing is bone stock. I dunno the gearing or anything, but I would think it should get around 9-10, maybe more. Now, the 87 is bone stock except for a body lift, 33s and 3.73s. I know a posted about the torque and all, but this is a more important matter, since I can't keep dishing out $40 a week to feed this thing. I'm gonna try to check the gearing this weekend if possible. My other friend brought up the fact that it has ESC. and that ESC is crap and I should ditch it... is this true? Help! I need to get this problem resolved fast.. I'd rather dump $500 into a smaller carb, an intake and a new dist than keep feeding the thing gas.

    <A target="_blank" HREF=http://billybob87k5.50megs.com>Homepage of Porky & Stinky</A>
    Billybob, the REAL <font color=red>Bionic Redneck</font color=red>
     
  2. Payador

    Payador Newbie

    Joined:
    Jul 6, 2001
    Posts:
    2
    Likes Received:
    0
    Location:
    Ohio
    Re: Super bad mileage

    I can relate! But I have a holly 600, on a 350 Crate Motor and my Blazer gets horrible gas mileage. I was told that a Q-Jet is better for gas mileage due to the fact that is has smaller primaries. I run headers/Flowmasters and 3:73 gears 33" tires. I figure thats why my gas mileage Sux
     
  3. BlazerGuy

    BlazerGuy 3/4 ton status

    Joined:
    Apr 20, 2000
    Posts:
    9,206
    Likes Received:
    0
    Location:
    abcde
    Re: Super bad mileage

    I have a stock 84 and I get 12ish mpg. How long has it been since you performed a through tune-up? Every time my K5 starts eating gas like it's going outta style it's time for a tune-up. Also the carb may need a rebuild.....

    Murphy's Laws on Life:
    "A bird in the hand is worth three Kleenex."
    <A target="_blank" HREF=http://www.K5.rockcrawler.com>http://www.K5.rockcrawler.com</A> *under construction*
     
  4. Pugsley

    Pugsley 1/2 ton status

    Joined:
    Jan 16, 2001
    Posts:
    3,556
    Likes Received:
    0
    Location:
    Tucson, Arizona
    Re: Super bad mileage

    A full tuneup and a carb rebuild should cure your ills. Q-Jets tend to start sucking gas like a crazed Arab when they need a rebuild, so I'd try that first. Also it might help to give the choke a thorough checkup/cleaning.

    <font color=red>Cripplefight!!</font color=red>
    <A target="_blank" HREF=http://pugsley.alloffroad.com>http://pugsley.alloffroad.com</A>
     
  5. BillyBob

    BillyBob 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    557
    Likes Received:
    1
    Location:
    Dumont, NJ
    Re: Super bad mileage

    That's another weird thing.. my choke light used to stay on for a bit.. then I changed the air cleaner, and it doesn't stay on after I turn on the truck. Also, it's starting to become a pain trying to start it in the morning.. But I know that the choke is working b/c the truck is idling high.. sometimes it still is after I get to school in the morning (30 min drive, half highway, half local driving) So I guess it's the Carb then

    <A target="_blank" HREF=http://billybob87k5.50megs.com>Homepage of Porky & Stinky</A>
    Billybob, the REAL <font color=red>Bionic Redneck</font color=red>
     
  6. Fish

    Fish Registered Member

    Joined:
    Jul 5, 2001
    Posts:
    34
    Likes Received:
    0
    Location:
    Michigan
    Re: Super bad mileage

    Is your cat plugged up? I had one that was so bad it would vent exhaust back up through the carb. Just a thought.
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Super bad mileage

    If the choke is staying on after the truck is warm it will do this. It will also idle poor. That Mix control car is also prone to having problems that kill economy. My 79 get's 12 hwy and that's with a TH350. Your truck with the over drive on the hwy should get 14 if it's tuned right, baring lift, gearing tires etc.

    It's not my damn planet monkey boy!
    <A target="_blank" HREF=http://communities.msn.com/OffroadK5s>http://communities.msn.com/OffroadK5s</A>

    Grim-Reaper
     
  8. BillyBob

    BillyBob 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    557
    Likes Received:
    1
    Location:
    Dumont, NJ
    Re: Super bad mileage

    yeah, the truck idles like crap. So, the stuck choke means....? do I need to rebuild it?

    <A target="_blank" HREF=http://billybob87k5.50megs.com>Homepage of Porky & Stinky</A>
    Billybob, the REAL <font color=red>Bionic Redneck</font color=red>
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Re: Super bad mileage

    Might not. Might need cleaning or the choke element may be bad. I would hose it down with carb cleaner and make sure none of the linkages are cruded up.
    With it stone cold fire it up with the air cleaner off and watch the choke and see if it is opening. If it isn't opening then get a Meter or test light and make sure it's getting 12v.
    Now the engine has to be running to get 12v. There is a oil pressure switch in line that controls that. This is so that if you turn the key to on but don't start the engine the choke will not cycle. No 12v then start looking for blown fuse. Trace the wire from the choke back to the oil pressure switch and check to see if there is 12 before the switch. If 12v there then the switch may be bad. That circuit also is where the mix control solonoid get's it's power so again if no powere the solonoid is not leaning out when warm and again more milage problems.
    If you got the 12v then put an index mark on the coke control and loosen the 3 scres that hold it in. give it a 1/4 turn and back a couple times. That element grounds to the housing and I have had one form electrolis and loose the ground. Moving it back and forth should be enough to clean the lip and get the ground back. Then set it back to the index mark and fire it up again and see if it cycles.

    It's not my damn planet monkey boy!
    <A target="_blank" HREF=http://communities.msn.com/OffroadK5s>http://communities.msn.com/OffroadK5s</A>

    Grim-Reaper
     
  10. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    Re: Super bad mileage

    Also if you have been running way rich, all that carbon and unburned gas has probabally ruined your 02 sensor. after you get the carb fixed replace the 02 sensor.

    <font color=orange>GOT HORSEPOWER?</font color=orange>
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Super bad mileage

    Well lets see....'84, no computer controled carb. With your symptoms, probably choke related, if not other things. Check choke out. Should be off in 5 minutes or less. Electric choke pulloff time depends on vintage, vehicle, motor, etc. (as determined by GM)

    Check your gears in the glove box, if the sticker is there. List all the codes that have a first or second letter of "G". (like G80, GU2, etc) If not in the glovebox, check the wheelwells in the engine bay and try to read the tag there, if present.

    Bad mileage is NOT the norm, I am with you. Even 15mpg hits me in the pocket when it comes to 30 gallons @$1.50.

    with my '83, rebuilt Q-jet (by me) new plugs, wires, cap, rotor (all cheap chain store stuff like autolite, lifetime warranty wires, etc) 305 with over 140k on it, 700R4, 208, 3.08 gears (base gears for your '84 I'm pretty sure if your drivetrain is similar to mine) and 31" tires, I would pull down an entirely consistent 17mpg freeway, 10-13 city.

    With a better motor, one with compression lol, I probably would have gotten much better. Some Vortec heads wouldn't hurt either, but with gas prices hurting you, I'm guessing you can't afford to be just blindly dumping money into a problem.

    Choke problems can be a real bear to fix, but just don't go bending stuff..figure out what its doing, then ask here how to fix it, or what to do. There are more people on this board that know what they are doing with q-jets than there are in any one shop in any state I bet : )

    "Rebuild" (glorified gasket set) kit is under $25, and if the primary throttle needs to be bushed, you are looking at most about $40.

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: Super bad mileage

    Base gears in '84 were 2.73s.

    ESC could be the problem. It has the capability to retard the timing 20 degrees, so that could seriously destroy your mileage.

    I 2nd the clogged converter problem. Remove it and replace it or lose it.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Super bad mileage

    Base gears with what combo? I'm betting base gears with 4wd, 305, AC, 700R4 (probably about the most likely combo in '84 as well) were 3.08's, since those are the most common gears from the early 80's, on "standard" (no tow package, etc) K5's. Base gears should vary by engine among other things. Those might have been the "highest" gears offered, but obviously with 3.08's, 3.42's, and 3.73's available, whichever helped the truck meet MPG and emissions requirements would have been used.

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  14. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: Super bad mileage

    I'm not trying to create an arguement here. I'm the one with the '84 here.

    The GU1 code gears in 1984 were 2.73. Under my hood on the left side inner fender it says, "Rear axle -- Standard ratio" and they were 2.73s.

    I have 4.10s now.

    And my truck came from the factory the same as you describe, 4wd, 305, AC, 700R4. And the 700R4 was an option...a TH 350 was still offered in '84.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Super bad mileage

    Nope, no argument. If thats what you had, thats it! : ) Just surprised that my '83 with same setup was 3.08. Just a year difference I guess. Just give you that much better mileage, IF a 305 can push a K5 to 60mph in OD...methinks 3rd would be the typical gear for most driving with that rear axle.

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  16. Jason73K5

    Jason73K5 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    592
    Likes Received:
    0
    Location:
    Fresno, Ca
    Re: Super bad mileage

    Thats not too bad. I once averaged 3 MPG in my K-5 between Texas and California!
     
  17. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: Super bad mileage

    Mine isn't a K5, but I'm pretty sure they're the same.

    I doubt that 2.73 or 3.08 gears give good mileage with ANY size tires or motor. I'd say that 3.42s are probably the best with the stock 235/75R15s or 31x10.50R15s.

    And my friend's 86 K5 also has 3.08s, so does my other friend's '86 K10 shorbox.

    Ratios for '84 were:
    2.73, 3.08, 3.23, 3.42, 3.73, or 4.10. That's for 1/2 ton trucks, but I'm sure that goes for K5s too, same thing.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Super bad mileage

    I can't agree with the mileage thoughts :) I got 17 freeway no problem with mine...even loaded with garbage I got that. City sucked bad (10-13) but like you said, lower gears (3.42's or 3.73's) would help out for a mostly city driver.

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     
  19. BillyBob

    BillyBob 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    557
    Likes Received:
    1
    Location:
    Dumont, NJ
    Re: Super bad mileage

    Okay, so I went to inspection Saturday just so I could get an extention on the time to fix the thing. And, sure enough, I failed. The main problem was Carbon Monoxide. the CO was around 2.97% or something like that. I would have passed if the CO was under 1. something or another. Does this mean the carb is running rich?

    <A target="_blank" HREF=http://billybob87k5.50megs.com>Homepage of Porky & Stinky</A>
    Billybob, the REAL <font color=red>Bionic Redneck</font color=red>
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,980
    Likes Received:
    189
    Location:
    Roy WA
    Re: Super bad mileage

    Can be a rich condition. Was this an idle/dyno test? If so, which did it fail? Alcohol in the gas can work wonders as well : )

    Dorian
    My tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
    No anti-theft measures on your truck? No pity when its stolen
     

Share This Page