5-6 mpg?!

[capt512]

Hey Everyone,

So I'm getting really bad gas mileage and trying to figure out how "normal" it is or isn't.

So here are the details-

03 300A with 84K on it. Had all original everything but fluids. Didn't pay much attention to mileage when I test drove it for a baseline but here is the current configuration. Less than 250 miles since owning.

New Motorcraft Airfilter (from dealer, marauder filter)
Had worn out vacuum hose going into intake tube, replaced with ford part.
New NGK 7164 Iridium TR55IX plugs
Royal Purple Oil
New Motocraft PCV
MAF Cleaned with MAF cleaner
Lots of oil in intake it appears
First week or so I had the car the passenger upper cat made a very slight noise for 1 second on startup, no longer makes any noise.
Was slow to start 1st week of ownership, now starts right up.
Very slight miss at idle with AC on max (as in very slight, not going to show on any machine)
No codes
Doesn't smell like its running rich etc

Car is driven city only, aproximately 15 miles total a day 5 days a week (to and from work).
AC has been on 75% of the time? for the last 2 tanks. Tank is refilled when it hits half.
Driving style is "sporty", not drag racing or WOT from stops, no burnouts, etc. Driven 40MPH average, 2 hills (nothing HUGE), 2 stoplights.

I am averaging 5-6MPG.... Now in comparison I drove a 01 CVPI prior, and my father has a 00 CVPI. I got about 13-14MPG average in it with 3.27 gears and a tune, similar driving style...maybe harder actually with the 01. Father drives his 00 with 3.55 gears real easy, gets same 13-14MPG.

So thoughts?

MODS - If this should be in shop talk please move...didn't know which it fit better...

[MOTOWN]

well this could be a tuffy! first off that mpg is wayyy far off from the norm! your slight miss could be a coil getting ready for retirement, and/or a bad coil on plug connector

i would check for any other possible vacuum leaks broken/or frayed vauum lines

check your cats to make sure the brick isnt pluged, or about to break loose within the housing

[capt512]

The COPs had never been pulled (original plugs even) when I got it, and had no boot cracks, etc in them. I have a feeling the slight miss is from the NGK plugs? as I sure don't remember it on the drive from OK to MO when I bought it.... No other hoses that looked bad when I checked them, will look again. Do need to change throttle body gasket as it looks to maybe have a tiny leak... No rotten egg smell, or hot floor boards, not marble in a can rattle, etc from cats...any other way to check? Car still runs hard etc.

[slickster]

I think a tuner can tell you the fuel and air ratio to see if it's even. I think a inspection can tell you the air fuel ratio. I think the dealer has a more in debt data obd scan that does not just pick up cel but about how that car is specific. Try the sea foam thing. Get a k&n filter. Replace your fuel filter. Try not to come to a complete stop. Mods that will ad mpg. Electric water pump. Pullys. Hooker max flow mufflers or aero turbine. Make sure the plugs are gap right. Lots of cheap gas can clog a cat maybe it's the inner cone in the cat breaking that you herd

[MOTOWN]

plugs shouldnt cause a miss, unless one was torqued so hard it broke, which i doubt is the case, it sounds like your miss is a coil, or coil on plug connector, thats where i would focus my attention, which would also cause the severe nose dive in mpg you speak of.

[slickster]

+1........

[Bradley G]

I had a misfire that was corrected by replacing two plugs(only).
plugs shouldnt cause a miss, unless one was torqued so hard it broke, which i doubt is the case, it sounds like your miss is a coil, or coil on plug connector, thats where i would focus my attention, which would also cause the severe nose dive in mpg you speak of.

[RacerX]

Injector stuck open/static. Possibly... Check all plugs and see if there's any color difference to each other.

[MOTOWN]

I had a misfire that was corrected by replacing two plugs(only).

well i guess a plug could fail, but ive never had that happen with a new set of plugs, and NGK are some of the best

[MOTOWN]

The COPs had never been pulled (original plugs even) when I got it, and had no boot cracks, etc in them. I have a feeling the slight miss is from the NGK plugs? as I sure don't remember it on the drive from OK to MO when I bought it.... No other hoses that looked bad when I checked them, will look again. Do need to change throttle body gasket as it looks to maybe have a tiny leak... No rotten egg smell, or hot floor boards, not marble in a can rattle, etc from cats...any other way to check? Car still runs hard etc.

just wondering how long have you had these plugs in? i know you said they are new

[capt512]

Not trying to make a focus out of a marauder or expecting crazy good gas mileage. I would be plenty happy with 12MPG or similar. No real inspections here (honk the horn, check the lights....thats pretty much it) to let me know. I may have the dealer run it, but all my experiences with them doing the stress tests, and sensor readings have just been $99 in the trash, as they can't ever find anything or tell me any results really.

Do plan to try the Seafoam thing...may even need to pull intake as well, as one of my other threads showed a massive amount of oil in intake.
Also plan on doing fuel filter very soon. Have run a bottle of techron through it, but no difference.

When I pulled the factory plugs out they were all the same color, no oil on them, actually were in very good shape.

I put the plugs in less than 250 miles ago, did check gap and they were on, also aren't gappable plugs.

[IwantmyMMnow!]

...so I will make my 'suggestion' based on the level of my knowledge...

Maybe a hole in gas tank or leak in fuel line? You said you fill up when it gets to 1/2 tank...maybe let it get below 1/4 tank and see if your MPG is the same? Also, what numbers are you crunching to get your MPG?

"From the mouths of babes..."

[RacerX]

Is the PCM stock or does it have a tune in it?

[MOTOWN]

i still think its a coil, coil on plug connector, if you have a fuel pressure gauge connect it to the fuel rail (drivers side) if you have a bad/stuck injector it wont hold pressure when you shut it off hence stuck injector

also as mentioned if you havent changed the fuel filter do so

[JoeBoomz]

Try cleaning the MAF with a spray cleaner for MAF or electronics contacts. Or the MAF might be bad. This will be easier to try first than any coils or plugs. Do the brakes stink or smell of burning when you come to a stop? One might be stuck...

Mine does about 21MPG on the hwy, and that's with 4:10 gears and some spirited passes.

[capt512]

I will check the gas tank and fuel line as well, though I would think I would see fuel on the ground for the amount of fuel that would have to be leaking...? To get my MPG I take my trip meter (reset at every fill up) and take how many gallons of fuel it takes to refill the tank to fuel, then divide the trip by the gallons to get MPG.

PCM is stock

Motown - Not arguing against the COP theory, just hoping to get some other ideas too. As the only way I know of to fix that is to get a whole new COP set (as having owned many COP platform vehicles previously, hunting one down can be near impossible), as the miss is not near enough to show on anything or for many people to even notice.

I don't have a fuel pressure gauge....I could get one I guess...

[capt512]

Have already tried cleaning MAF with MAF cleaner, no change. Anybody know what the voltage should be on a good MAF? I know one of the CV guys had found a tech article with the voltage for a clean MAF, but it was for 00 and older.

No hot brakes or stinking brakes, emergency brake cable doesn't appear to be stuck on either.

[Got_1]

get an infrared temperature gauge and check your cats to make sure theyre not plugged. measure temps just before cat and after cat. there should be about 100*F difference (hotter on the after side)

you also will want to get your O2's checked out. your car is probably staying in open loop the majority of your short drive each day. If your O2's are old and slow then this will cause horrible fuel mileage.

[EMAS]

Wow that is some really really bad MPG. The worst I've managed is mid 17 and my driving is mainly city type and I drive it pretty hard. Heck even with my old CV with heavy use of the remote start to warm up or cool down the interior and/or other extensive idling the worst I've seen was 16. Do you do extensive amount of idling either to warm up or other times?

A single cyl missing ocassionaly isn't going to cause that bad of MPG. A miss does cause the engine to run rich as that cyl with unburnt fuel also contains a bunch of oxygen which the O2 sensor sees as a lean condition. Even still the worst case secanario should only cause a loss of maybe 30-35% in MPG as that is all the extra fuel the computer can add. With that much extra fuel the engine would be very rough running the cats will likely be glowing red and there will be a strong fuel smell from the exhaust. In any case you should have the check engine light on with a code for the missing cyl, O2 sensors that show up as always lean or an adaptive limit reached code. A single or a couple of injectors that are not closing properly also aren't going to cause that much of a loss of MPG. The only thing that makes much sense is a fuel leak.

I'd recommend a careful inspection of the fuel system for leaks and if nothing is found there you need to have it hooked up to a scan tool with live data capability and have someone that specializes in "no-code" driveablity diagnosis watch what the computer is doing.

[FordNut]

Where do you park? Is somebody stealing your gas?

[burt ragio]

Has there been a gear or torque converter upgrade ?

[capt512]

EMAS - Kinda what I was thinking that what makes me wonder, driveability wise nothing seems bad enough, so it has to be something I'm not seeing....
During deep winter I remote start my cars, but these are with no idling, just drive time.
Don't know why I never get better mpg than that, but we don't. My 01 has the marauder cluster installed, and I even drove it for a week with the tach under 1500RPM at all time (which was very hard to even get up to speed), not coming to a complete stop, etc for ideal MPG to see how good I could get and only got 15MPG. Maybe Kansas City gas is bad or something? I have used multiple different gas stations and have the best luck with phillips.

Fordnut - Strongly doubt gas theft, as at work the car is watched by myself constantly on camera, and at home its parked back behind the hose where its not even visible to anyone but me. And I have the remote fuel door, but no pry marks anywhere.

burt - nope, 2nd owner before me and he said everything is stock...which I would believe. And I haven't done any mods like that. Was gonna do 4.10s in the future...but gotta get this figured out first.

[Blackened300a]

Just to be certain. When you fill up your tank, how many gallons of gas does it take and do you wait for the light to come on or do you run it til its below the "E" ? The gauge on 300A's have been known to show less gas then whats actually left in the tank.

[RacerX]

Just to be certain. When you fill up your tank, how many gallons of gas does it take and do you wait for the light to come on or do you run it til its below the "E" ? The gauge on 300A's have been known to show less gas then whats actually left in the tank.
Damn! Forgot about that one! Mine is one of those 300as that do that! ;)

[capt512]

I don't every wait for the tank to go to E or light to come on so I won't pick up any sediment, I am just taking the amount of gallons used to refill tank and the trip meter to show distance.

[fastblackmerc]

How to calculate fuel economy from the 2004 Marauder owners manual.

Calculating fuel economy
1. Fill the fuel tank completely and record the initial odometer reading
(in kilometers or miles).
2. Each time you fill the tank, record the amount of fuel added (in liters
or gallons).
3. After at least three to five tank fill-ups, fill the fuel tank and record
the current odometer reading.
4. Subtract your initial odometer reading from the current odometer
reading.
5. Follow one of the simple calculations in order to determine fuel
economy:
Calculation 1: Multiply liters used by 100, then divide by total
kilometers traveled.
Calculation 2: Divide total miles traveled by total gallons used.
Keep a record for at least one month and record the type of driving (city
or highway). This will provide an accurate estimate of the vehicle’s fuel
economy under current driving conditions. Additionally, keeping records
during summer and winter will show how temperature impacts fuel
economy. In general, lower temperatures give lower fuel economy.

[RF Overlord]

Something huge is being overlooked. 5-6 MPG is less than a THIRD of the car's EPA rating. Yes, I know those are not hyper-accurate, but come on...a THIRD? For a car to get that kind of atrocious economy, it would have to be running like smashed ass. This isn't going to be a "clean your MAF" or "replace a COP" kind of problem...it's got to be something outside-the-box.

[capt512]

thats pretty much the same way I calculate, just I don't do 3-4 tanks as that would be about 400-500 miles which as little as I drive would be a month and a half worth of driving, kinda hard to gauge whether things worked that way. Its the same system though.