Well, new K&R air filter, new sparkplugs, mechanic says no problem with compression or ECS, brakes aren't rubbing, clutch isn't slipping, I'm not burning the tires on starts. Engine starts fine, idles REALLY smoothly, plenty of power. Tires are new, balanced, aligned, properly inflated.
But I'm getting about 16mpg in the city (should be 22). I can almost see the fuel gauge go down as I drive!
Any suggestions? Truck is 1990 2wd, 4-cyl (KA24E), 5-spd manual with alum. canopy.
Lloyd
Last edited by druid : Jan 23rd, 2005 at 07:09 PM.
One thing: There's a "canister" or something at the end of the air inlet that the Totally Useless Hayes manual makes no reference of. There's the air filter, a black pipe, and the pipe goes into this..."thing" where I assume the air comes in. I'm thinking of taking the pipe off this thing and see if the milage improves, but I'd like to know what it is and what it does before I disconnect it.
Anybody know what is is and what it does? It's in the front left of the engine compartment.
One thing: There's a "canister" or something at the end of the air inlet that the Totally Useless Hayes manual makes no reference of. There's the air filter, a black pipe, and the pipe goes into this..."thing" where I assume the air comes in. I'm thinking of taking the pipe off this thing and see if the milage improves, but I'd like to know what it is and what it does before I disconnect it.
Anybody know what is is and what it does? It's in the front left of the engine compartment.
Lloyd
I don't know, but I think it's just a "muffler" for the intake. It keeps all those sucking and other noises quiet.
So, have you changed the fuel filter, PCV, cap & rotor, plug wires, O2, and things of that nature?
What size tires do you have?
__________________
Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd
I don't know, but I think it's just a "muffler" for the intake. It keeps all those sucking and other noises quiet.
So, have you changed the fuel filter, PCV, cap & rotor, plug wires, O2, and things of that nature?
What size tires do you have?
Well, if it's a muffler, it's history!
Wouldn't a dirty fuel filter give me BETTER milage (but poorer performance...)?
The Mechanic assured me the ignition was fine after replacing the plugs. Also, if ignition wires, O2 sensor, etc. were the culprit, wouldn't the engine run poorly? Remember, we're talking a HUGE difference here, not just a few mpg.
Haven't ruled out the O2 sensor, though - I might get enthusiastic and try to figure out the ECS...
Tires are 205/75R14, and speedo seems to be almost exactly right.
Lloyd
Last edited by druid : Jan 23rd, 2005 at 09:25 PM.
That's nearly right at stock MPG quotes from the factory, actually. You know when they test those things for mileage, they run at 50 MPH on a downhill slanted road at or below sea level to get those figures...on a brand-new(though probably broken-in) engine and tranny with synthetic oil in everything....in other words, realistically you might never see better mileage. Nissan trucks never do, from what I've seen. Too heavy, cammed for the wrong power/torque range, and smog-legal all spells low mileage.
__________________
Owner of NPORA, mod for Nissan-Infiniti Forums, NissanForums.com, NissanHelp.com, AllNissans.com and VGPowered Forums
'88 Pathfinder: 6" of lift, 33x13.50 Swamper LTB's, Rancho 9000's, L&P Stage 3 steering system, K&N, Pacesetter headers and 2.5" exhaust, Lock-Right locker, 110A alty and electric fan swap, dual batteries, 700W+ worth of PIAAs, etc.
That "muffler" is called a resonator, jerryp58 is correct! all it does is keep things quiet.. but keep it just in case you need it for emissions testing. I would look at the 02 sensor, do you have a factory cap/rotor on it? sometimes it will arch and burn a hole in a aftermarket cap. or sometimes if the wires are old, it might be grounding out on the valve cover, some thoughts anyway
Wouldn't a dirty fuel filter give me BETTER milage (but poorer performance...)?
I don't think it necessarily would. I may idle rough, but the computer may have to do weird things to compensate for the lean mixture.
The Mechanic assured me the ignition was fine after replacing the plugs. Also, if ignition wires, O2 sensor, etc. were the culprit, wouldn't the engine run poorly? Remember, we're talking a HUGE difference here, not just a few mpg.
Again, it may run poorly, but it may not really be that noticeable. If they've got a lot of time and/or miles on them, it wouldn't hurt to change them (wire, cap & rotor, PCV, filters, etc.).
Haven't ruled out the O2 sensor, though - I might get enthusiastic and try to figure out the ECS...
Tires are 205/75R14, and speedo seems to be almost exactly right.
It's probably silly to ask, but they are radials, right? Correct pressure?
Lloyd
Theoretically, opening up the intake (the K&N should help a bit) and the exhaust (a CAT back system and a properly functioning catalytic converter) should help.
How does it do on the highway?
__________________
Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd
That's nearly right at stock MPG quotes from the factory, actually.
EPA figures for that truck/engine/trans is 22/27 mpg. My Lady has a 240SX with almost the identical engine (Nissan tweaks it to get an extra 20 hp), and same weight. She gets 22-24 in the city. I asked on this forum what others with this truck get, and the consensus was around 24 or so "combined" (4wd was MUCH lower!).
I'm getting 16.
This isn't just a few mpg that could be explained away by incorrect tire pressure, or "EPA figures always exaggerate".
It's also not O2 sensor, wiring, dist cap. etc. If they were THAT bad, the engine would stumble, miss, have no power, hard to start, etc. And it runs fine. Also, we have a mandatory emissions test here called "aircare", and the low figures show there's no raw gas (Hydrocarbons) or improperly-burned gas (CO) in the exhaust. These figures would be WAY higher if there was a problem with ignition or O2 sensor. Anyway, the mechanic checked all these things and they're fine (except for the plugs, which he replaced with NGK)
Haven't had a chance to really get out on the highway for a tankfull and see how it performs there, fuel-wise. Smooth and plenty of power, though...
I had a rude awakening today. When I took my 92 in for what I thought to be universals. I found, on my model anyway, that there are no universals made. The whole drive shaft had to be changed. After doing this my gas mileage went from 23/24 to 28mpgs.
I had a rude awakening today. When I took my 92 in for what I thought to be universals. I found, on my model anyway, that there are no universals made. The whole drive shaft had to be changed. After doing this my gas mileage went from 23/24 to 28mpgs.
Yeah...I've heard you have to replace the entire driveshaft (and there's some other problem too - something about making SURE you have the right length...?). In my case, Mechanic checked the driveshaft/universals and they're fine (along with the tranny and diff fluids)
So - are those figures US MPG? City? Highway? "Combined"?
Well, maybe I wasn't calculating right, or the speedo was off, or it was winter, but NOW, I'm getting about 20 city and 24 "combined". Good enough for me! Thanks for all the help.
Well, maybe I wasn't calculating right, or the speedo was off, or it was winter, but NOW, I'm getting about 20 city and 24 "combined". Good enough for me! Thanks for all the help.
Lloyd
Well, my 89 hardbody is getting about 18 right now, I know it's way off. From what I have read so far a clogged catalytic converter can cause poor fuel economy but still pass emissions....that's the next thing I am checking out after I do a tune-up...
Dang, I'd feel priveleged to get 18 out of any of my vehicles except the Impulse. Try tapping on your cat, if it rattles or makes salt-shaker noises, it may have disintegrated inside and need replacing.
__________________
Owner of NPORA, mod for Nissan-Infiniti Forums, NissanForums.com, NissanHelp.com, AllNissans.com and VGPowered Forums
'88 Pathfinder: 6" of lift, 33x13.50 Swamper LTB's, Rancho 9000's, L&P Stage 3 steering system, K&N, Pacesetter headers and 2.5" exhaust, Lock-Right locker, 110A alty and electric fan swap, dual batteries, 700W+ worth of PIAAs, etc.
Well, maybe I wasn't calculating right, or the speedo was off, or it was winter, but NOW, I'm getting about 20 city and 24 "combined". Good enough for me! Thanks for all the help.
Lloyd
Cool, the cheapest fix yet; a calculator with bigger buttons
__________________
Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd
Dang, I'd feel priveleged to get 18 out of any of my vehicles except the Impulse. Try tapping on your cat, if it rattles or makes salt-shaker noises, it may have disintegrated inside and need replacing.
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