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IamDave0887

97 Sable 3.0 Vulcan Poor Fuel Mileage

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Hello there,

I'm Dave and i'm trying to figure something out on a 97 Mercury Sable with the 3.0 Vulcan engine.

My girlfriend just bought this car in July '12 with ~172,000 miles on it. It currently has ~175,500 for mileage.

She has reported poor mileage in the city(~12-14 mpg), but decent on the highway save for the last highway trip. The mileage was poor if not worse.

When she came out to CT from IL, which is about 1,000 miles her fuel economy was excellent.

The last tank we ran 89 octane fuel, normally we run 87 octane.

The car has been throwing a random P0430 here and there. The odd thing is, sometimes we can go a few weeks with no MIL and no codes, other times it pops up 5 minutes after clearing the code.

I hooked up my scanner today(Innova 3130c) and took a look at the fuel trim percentages in the live data.

STFT [percentage for both Bank 1 and Bank 2 seem to hover around 0.0% going a bit positive or negative randomly, but always returning right around 0.0%.

LTFT percentage for both banks on the other hand goes right up to +18% to +21% upon starting the engine and stays in that range.

If i'm reading this right the PCM is trying to richen the fuel mixture due to a percieved lean condition.

I've done the basics already. New plugs(genuine Motorcraft), wires, fuel filter, air filter, etc. New t-stat and water pump due to bad WP bearing.

I"m unsure if the Cats, O2s, etc are original or not. We have no history on the car.

I"m wondering if the O2s are poisoned, or perhaps they are just dead.

I plan to check fuel psi and check for vacuum leaks as soon as i can find my fuel pressure tester.

The car seems to start and run ok, although the idle seems a bit rough. Every so often it sounds like a cyl will skip once. It's noticeable due to the hole in the muffler that i need to replace.

Any information you folks can provide would be very helpful. We can't keep getting such poor mileage with this car. Hell my '85 K-5 Blazer gets better mileage and that's with a 6.2L turbo diesel. Something isn't right here.

Thanks,

- Dave

Edited by IamDave0887

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Replace the coil pack with a new one, check the idle air control valve and replace if needed, some would say seafoam it, others will say avoid it, do so at your own risk. New PCV valve too, also did you reset the entire car, unplug the battery and pump the brakes, returning 30+ mins later (preferably overnight)

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Hello there,

I'm Dave and i'm trying to figure something out on a 97 Mercury Sable with the 3.0 Vulcan engine.

My girlfriend just bought this car in July '12 with ~172,000 miles on it. It currently has ~175,500 for mileage.

She has reported poor mileage in the city(~12-14 mpg), but decent on the highway save for the last highway trip. The mileage was poor if not worse.

When she came out to CT from IL, which is about 1,000 miles her fuel economy was excellent.

The last tank we ran 89 octane fuel, normally we run 87 octane.

The car has been throwing a random P0430 here and there. The odd thing is, sometimes we can go a few weeks with no MIL and no codes, other times it pops up 5 minutes after clearing the code.

I hooked up my scanner today(Innova 3130c) and took a look at the fuel trim percentages in the live data.

STFT [percentage for both Bank 1 and Bank 2 seem to hover around 0.0% going a bit positive or negative randomly, but always returning right around 0.0%.

LTFT percentage for both banks on the other hand goes right up to +18% to +21% upon starting the engine and stays in that range.

If i'm reading this right the PCM is trying to richen the fuel mixture due to a percieved lean condition.

I've done the basics already. New plugs(genuine Motorcraft), wires, fuel filter, air filter, etc. New t-stat and water pump due to bad WP bearing.

I"m unsure if the Cats, O2s, etc are original or not. We have no history on the car.

I"m wondering if the O2s are poisoned, or perhaps they are just dead.

I plan to check fuel psi and check for vacuum leaks as soon as i can find my fuel pressure tester.

The car seems to start and run ok, although the idle seems a bit rough. Every so often it sounds like a cyl will skip once. It's noticeable due to the hole in the muffler that i need to replace.

Any information you folks can provide would be very helpful. We can't keep getting such poor mileage with this car. Hell my '85 K-5 Blazer gets better mileage and that's with a 6.2L turbo diesel. Something isn't right here.

Thanks,

- Dave

P430 is cat perform below normal. Bank 2.

Needs replaced.

High Long Term Fuel Trim likely low fuel pressure.

Filter change before checking.

Other causes of poor mpg.

1 dragging brakes. At that age, likely guide pins stuck on front discs.

For rears, parking brake cable.

Easy check for dragging.

Park overnight on level with parking brake on.

Start and let it idle for a few seconds, put it in gear, relase the parking brake. It should roll free on level pavement. It if seems to move slow: Re do without the parking brake next night. If it still draggs, look for front caliper pins tight. If it draggs only after the parking brake has been used, look for the cable to be sticking.

-chart-

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P430 is cat perform below normal. Bank 2.

Needs replaced.

High Long Term Fuel Trim likely low fuel pressure.

Filter change before checking.

Other causes of poor mpg.

1 dragging brakes. At that age, likely guide pins stuck on front discs.

For rears, parking brake cable.

Easy check for dragging.

Park overnight on level with parking brake on.

Start and let it idle for a few seconds, put it in gear, relase the parking brake. It should roll free on level pavement. It if seems to move slow: Re do without the parking brake next night. If it still draggs, look for front caliper pins tight. If it draggs only after the parking brake has been used, look for the cable to be sticking.

-chart-

I installed new front and rear pads, rotors, hardware, and rear calipers back in august. Re-lubed front calipers and there was nothing sticking after i was finished.

Parking brake cables were not sticking as they moved freely when i had the old calipers off. I made sure to check that.

Fuel filter is less than 2 months old and doens't even have 2,000 miles on it.

the P0430 seems to be random. It never came on during her drive from IL to CT. Only after that.

Have yet to check for vac leaks, but the constant LTFT being high doesn't make any sense. It should be trying to get as close to 0.0% as possible, not floating between +18 to +21 percent on both banks like it does.

Edited by IamDave0887

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I installed new front and rear pads, rotors, hardware, and rear calipers back in august. Re-lubed front calipers and there was nothing sticking after i was finished.

Parking brake cables were not sticking as they moved freely when i had the old calipers off. I made sure to check that.

Fuel filter is less than 2 months old and doens't even have 2,000 miles on it.

the P0430 seems to be random. It never came on during her drive from IL to CT. Only after that.

Have yet to check for vac leaks, but the constant LTFT being high doesn't make any sense. It should be trying to get as close to 0.0% as possible, not floating between +18 to +21 percent on both banks like it does.

Do not expect to see LT trims to be zero.

Pic of my Lin Cont with 50K miles and it is HAPPY!

One of my Sables runs about the same amount negative and it is happy also.

A vacuum leak will cause a positive at idle but not much under load.

Low fuel pressure will cause high across the range of driving.

I think +30% is the limit and it will set a code for that.

Long term just adjusts for the car's personality to keep short term near the center of it's range.

I would not be surprised to see a bad cat cause a code sometimes and not others.

Usually it takes two events to set a code. So you can have a pending code and not set the light.

If the cat caused excess back pressure, it would be on one bank only and your trims would be different from bank to bank.

However, my long term trims do not agree on any of my 3 cars. There is a personality from side to side that is normal.

Well, normal for mine.

-chart-

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I agree with chart here. Check the fuel pressure. Vacuum leaks usually only pop the fuel trims up at idle. As soon as you give it some gas they go right back down to normal or near normal range.

If it is fuel pressure, you may start seeing a P0300 pop up, or another misfire code. Do you have any problems starting the car (crank for several seconds before it starts)?

Edited by breeves002

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I agree with chart here. Check the fuel pressure. Vacuum leaks usually only pop the fuel trims up at idle. As soon as you give it some gas they go right back down to normal or near normal range.

If it is fuel pressure, you may start seeing a P0300 pop up, or another misfire code. Do you have any problems starting the car (crank for several seconds before it starts)?

The engine seems to start ok, but I haven't worked on any other vulcans other than this one. A few turns and it starts up when dead cold. when warm it starts with i'd say at most 1 full turn of the crankshaft. YOu barely have to touch the key when it's warm and it pops to life.

A check of vacuum pulling vac from the FP regulator vac line shows a steady hold at 17 in of Hg at idle. If i rev it hard it drops to 0 then climbs to ~20-21 then settles back to 17-17.5 and holds there.

The idle doesn't hunt, although i do hear a slight stumble every now and again.

I took carb clean and sprayed each and every vac line, connector, junction, etc and i heard no change in engine RPM. Perhaps i need something a little more potent for the engine to change it's RPM? I took carb cleaner and sprayed a 1/2 second burst directly into a main vac line and the engine RPM did change, it went high then stumbled for a second like it was choking then cleared out.

I don't know where to turn at this point. I have both pre-cat O2 sensors in the boxes ready to go, but i don't know if that will solve a thing or not.

I have to fix the oil pan gasket today. The front of the gasket right under the crank pulley is sticking out, like someone screwed up when they installed it. Amazingly it's not pouring oil out, but i'm going to see if i can just loosen the pan and shove the gasket back in. Found some good size holes in the driver's floor under the pedals yesterday, so i don't really want to dump a ton of money in this car as it's rotting away.

It's too bad, it seems to run very well save for the piss poor mileage.

Going out to test FP and FP regulator operation now.

One thing i just thought of, not sure if it means anything. When running and the engine is cold the air around the car stinks of a really rich running engine.

Anything else it could be?

Edited by IamDave0887

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The engine seems to start ok, but I haven't worked on any other vulcans other than this one. A few turns and it starts up when dead cold. when warm it starts with i'd say at most 1 full turn of the crankshaft. YOu barely have to touch the key when it's warm and it pops to life.

A check of vacuum pulling vac from the FP regulator vac line shows a steady hold at 17 in of Hg at idle. If i rev it hard it drops to 0 then climbs to ~20-21 then settles back to 17-17.5 and holds there.

The idle doesn't hunt, although i do hear a slight stumble every now and again.

I took carb clean and sprayed each and every vac line, connector, junction, etc and i heard no change in engine RPM. Perhaps i need something a little more potent for the engine to change it's RPM? I took carb cleaner and sprayed a 1/2 second burst directly into a main vac line and the engine RPM did change, it went high then stumbled for a second like it was choking then cleared out.

I don't know where to turn at this point. I have both pre-cat O2 sensors in the boxes ready to go, but i don't know if that will solve a thing or not.

I have to fix the oil pan gasket today. The front of the gasket right under the crank pulley is sticking out, like someone screwed up when they installed it. Amazingly it's not pouring oil out, but i'm going to see if i can just loosen the pan and shove the gasket back in. Found some good size holes in the driver's floor under the pedals yesterday, so i don't really want to dump a ton of money in this car as it's rotting away.

It's too bad, it seems to run very well save for the piss poor mileage.

Going out to test FP and FP regulator operation now.

One thing i just thought of, not sure if it means anything. When running and the engine is cold the air around the car stinks of a really rich running engine.

Anything else it could be?

A slow to get started converter could cause this. It is normal for a few seconds after starting to smell raw fuel smell out the exhaust, but only a short time till the converter lights off.

-chart-

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OK i'm back with a few more findings.

Fuel pressure seems good. engine off it jumps right to 40-42 psi and holds there. Starting the engine it sits right around 32-34 psi. A quick rev causes it to jump to 40 psi then drop back to 30-32 psi and hold there under throttle and when dropped back to idle.

I cleaned the MAF sensor with the proper cleaner, installed a new PCV, and changed the B2 S1 O2 sensor(behind the radiator). I haven't changed the B1 S1 sensor yet, but i have it if need be. The LTFT for B1 dropped a point or two down to around +18, and seems to jump towards 0 quicker now than it used to so i'm wondering if the old sensor was lazy. It was original as it said "Ford NTK" on it with a ford part #.

The old O2 sensor was white-ish gray on the sensor end. It looked like a properly burning spark plug would look, so perhaps i'm chasing the wrong thing?

I have a can of Seafoam here. i was debating feeding the main brake booster line with some of it to clean the intake out.

This car always seems to condensate out the exhaust. It doesn't have any smell to it other than regular car exhaust, but it seems excessive to me. Then again i own and am used to diesel engines which don't condensate out the exhaust for very long or unless well below freezing into the teens for temperature. Perhaps my view on this is skewed and what i'm seeing is normal.

EGR works as it should. Applying vacuum causes the engine to stumble at an idle and releasing it causes the engien to return to normal idle.

I did get pending lean codes for both banks when i hooked up my FP tester and held the "pressure release/drain" button in and let some fuel drain into a container.

I"m off to fix the oil pan gasket and change the oil now.

I haven't a clue what could be causing such poor mileage.

Edited by IamDave0887

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I'm thinking plugged converter(s), possibly fouled due to the lazy o2 sensors. The vacuum should be a little higher at idle, around 20 inHg, and the throttle snap should cause it to go up to 24-25 inHg on the return, with quick, smooth transitions.

Clogged muffler can do this also, try disconnencting the front y-pipe and doing the vacuum test. Use a port on the vacuum tree by the brake booster so it doesn't screw with the fuel pressure while testing.

Condensation is normal for all gas burners, the exhaust is generally cooler at exit than a diesel.

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I ran a few more tests the other day, just getting to post about them now.

Replaced PCV and re-installed the front lip of the oil pan gasket and fresh oil and filter. Barely any oil came out of the old filter so i'm guessing it was in bypass mode. the oil was basically pitch black too, so it had been in there for a while.

the LTFTs came down a few points when i fixed the oil pan gasket and replaced the PCV. To fix the gasket i had to drop the starter, so i unhooked the battery. I have yet to replaced the B1S1 O2 just yet. I'm having her drive it for a bit to see if anything that has been done increased the mileage back into the normal range.

How often, if ever, do these engines need their injectors replaced. A friend of mine had a '90 Corsica with the 3.1 V6 that needed injectors every year on the dot after about 300,000 miles but that was because they electrically failed.

With a good throttle snap the vac does go up to 23-24 inHg then drop back down. If i rev it to say 2,000 RPM the engine maintains good vacuum so if the converters are plugged it can't be by much. Plugged converters would cause pressure in the exhaust and cylinders eventually causing it to stall since it can't breathe out.

Edited by IamDave0887

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I ran a few more tests the other day, just getting to post about them now.

Replaced PCV and re-installed the front lip of the oil pan gasket and fresh oil and filter. Barely any oil came out of the old filter so i'm guessing it was in bypass mode. the oil was basically pitch black too, so it had been in there for a while.

the LTFTs came down a few points when i fixed the oil pan gasket and replaced the PCV. To fix the gasket i had to drop the starter, so i unhooked the battery. I have yet to replaced the B1S1 O2 just yet. I'm having her drive it for a bit to see if anything that has been done increased the mileage back into the normal range.

How often, if ever, do these engines need their injectors replaced. A friend of mine had a '90 Corsica with the 3.1 V6 that needed injectors every year on the dot after about 300,000 miles but that was because they electrically failed.

With a good throttle snap the vac does go up to 23-24 inHg then drop back down. If i rev it to say 2,000 RPM the engine maintains good vacuum so if the converters are plugged it can't be by much. Plugged converters would cause pressure in the exhaust and cylinders eventually causing it to stall since it can't breathe out.

Injectors seldom need replacing. I have had 7 Taurus/Sables and 5 Lin Con. Replaced one injector on '88 as it leaked when the engine was shut off. I got a used one at the Pick A Part and all was well. All the Taurus/Sables bought used, all went to my daughters when I got high miles on them. Others might chime in, but very little talk about injectors on posts.

Black oil and little in the filter is bad. If it gets dark quickly again, likely there is compression leaking around the rings.

-chart-

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Injectors seldom need replacing. I have had 7 Taurus/Sables and 5 Lin Con. Replaced one injector on '88 as it leaked when the engine was shut off. I got a used one at the Pick A Part and all was well. All the Taurus/Sables bought used, all went to my daughters when I got high miles on them. Others might chime in, but very little talk about injectors on posts.

Black oil and little in the filter is bad. If it gets dark quickly again, likely there is compression leaking around the rings.

-chart-

I'm going to run a comp test on it at some point, but it starts and runs well. I have a feeling the oil just wasn't changed. The last place she took the car to were a bunch of scumbags. They said the car was fine to drive 1/2 way across the country. The car had beyond rotten brake lines held together with comrpession unions everywhere, that leaked when i touched them, brakes were grinding on the rotors, and god knows what else.

Disgusting that they would put someones life at risk because they are idiots.

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I'm going to run a comp test on it at some point, but it starts and runs well. I have a feeling the oil just wasn't changed. The last place she took the car to were a bunch of scumbags. They said the car was fine to drive 1/2 way across the country. The car had beyond rotten brake lines held together with comrpession unions everywhere, that leaked when i touched them, brakes were grinding on the rotors, and god knows what else.

Disgusting that they would put someones life at risk because they are idiots.

Good case for "do it yourself" or at least, check everything others do to your car.

As to oil filters, they do not drain out easily.

I have a cheap screw driver I sharpened to a point.

I turn the old filter threads up and poke a hole or two in the rubber drain back valve.

Then turn it end for end and poke a hole in the metal.

Then thrun that down in my oil drain pan and leave it there until the next oil change.

It will be very light after a few days.

I have 3 cars and do 10 to 12 changes a year.

All use the same filter which I only use Motorcraft wtih (S) silicone valve.

All use different drain plug sizes so I paint mark the size on my filter wrench.

Also paint the fill Q near the filler on each car.

And paint mark on the inner fender the date and miles.

Old coots do not remember.

-chart-

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Haven't run any further diagnostics on the car in the last few days. She has been driving it back and forth to work since this weekend, which is about 12-13 miles one way.

Might change the B1S1 O2 on Saturday. Perhaps I'll run a comp test on the front cylinders then as well. One plug at a time and just un-hook the power to the coil.

Not sure what else could be causing the problem that hasn't been thought of or addressed.

Anything else you folks can think of that would contribute to such poor mileage?

Once the weather warms up i may drive her car a few days just to see if ia notice anything on a few back/forth trips to work.

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Man I've been having weird fuel economy lately as well. I'm sure I'm calculating it correctly and filling up fully. I got 14mpg one tank, then 16mpg the next, then 18mpg, then 19mpg, then 31mpg, then yesterday, back down to 12mpg! Yikes!!! Not sure why haha!

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Man I've been having weird fuel economy lately as well. I'm sure I'm calculating it correctly and filling up fully. I got 14mpg one tank, then 16mpg the next, then 18mpg, then 19mpg, then 31mpg, then yesterday, back down to 12mpg! Yikes!!! Not sure why haha!

Two things. Maybe your tank is not filling right, maybe your odometer is not working right.

-chart-

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Finally figured out some of the puzzle.

Changed the B2S1 O2 sensor. mileage went up to around 20 mpg with that sensor change.

I have the B1S1 sensor as well, but the old one will not come out. It's a factory sensor, so perhaps it was crossthreaded when installed.

It will turn 1-2 turns then it stops. I dn't want to force it.

A new dilema has popped up though.

This car is reg'd in Illinois, and canont be reg'd in CT due to the severe rocker panel rot, compression unions on various brake lines, and a hole in the driver's side floor pan. The car was like this when she bought it, and Illinois doesn't inspect cars so she reg'd it with no issues then.

It wouldn't pass the out of state vehicle inspection, and i know it.

We are debating parting the car out, or selling the whole thing for parts. It runs so well i'd hate to scrap it, especially since i've given it a full tune up, new WP and t-stat, coolant bottle, new rear struts/springs, etc.

I don't know what to do, as i can't sell it as a useable in state vehicle due to the body rot.

Junkyards wouldn't give much of anything for it as the car are so common i'd think.

Have to figure something out, and fast.

- Dave

Edited by IamDave0887

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Drive it to a state that doesn't have inspections, sell it for $1000 runs/drive. Take amtrack back.

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buy a rust free car and swap the good parts in. then sell the rusted out chassis for scrap

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Found out that my state dropped those inspections about a year and 1/2 ago. News to me.

Went to look at an '81 Mercedes Benz 300SD 5 cyl turbo diesel. Looking for something a bit more fuel efficient, and the 300SD was rated at 32.6 MPG. Lots of miles though. 297K and some change. Body looks pretty darn good. no rot, a few spots of surface rust, and it will need a new front bumper at some point. Current one is a little rotten in a few spots. It was originally a Louisiana car, so no heavy winter use unlike the current Sable.

Edited by IamDave0887

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Found out that my state dropped those inspections about a year and 1/2 ago. News to me.

Went to look at an '81 Mercedes Benz 300SD 5 cyl turbo diesel. Looking for something a bit more fuel efficient, and the 300SD was rated at 32.6 MPG. Lots of miles though. 297K and some change. Body looks pretty darn good. no rot, a few spots of surface rust, and it will need a new front bumper at some point. Current one is a little rotten in a few spots. It was originally a Louisiana car, so no heavy winter use unlike the current Sable.

Too many miles. Even for a diesel. Especially a Mercedes diesel. Finding parts for that thing will be misery.

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My cousin and his wife bought a Mercedes from the early 80's with low miles thinking it would last forever. They moved from Wisconsin to Missouri and they sold it because they realized if it ever broke there was no way of finding parts for it.

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