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Terrible fuel economy but no check engine light

323 Views 11 Replies 6 Participants Last post by  amc49
I recently bought my 2001 Focus Wagon and the seller stated he got about 7-8l/100km. I figured that might be low but was a bit surprised to only get 9.5.

I switched the plugs and cables that were quite old and it got worse at 11. So I rechecked the gap (which I hadn't done) and gapped them only to see it go up to 13. So I brought it to my mechanic who confirmed they were the correct plugs but found the PCB valve broken that they replaced. No change to mileage.

I then worried that I had broken the plugs when gapping, so I picked up and installed a new set and it dropped to 10.5, high, but a lot better than anything after I tossed the old crappy plugs. After a day of driving at -15 in the snow banks, it dropped the 12 and has been hovering around 11.5 ever since.

I used the NKG plugs and cables that were recommended by Lordco, no check engine light and my mechanic didn't find any other issue than the PCV valve and I did explicitly complain about the terrible mileage.

Any recommendation or thoughts? I bought this vehicle only in September and specifically didn't buy an SUV to save on gas! But right now, it used just as much as my old Outback and RAV4.
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Discussion Starter · #2 ·
In MPG, I got 24.7 before the plug exchange and after all the hassle (down to 17) I'm at 20.5 now. Having read a bit on the forum, it seems that most people get around 28-30 although I'm not sure if that's with the wagon
 

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My 2010 had a bad value cover leak ... and 21 mpg.

Replaced the value cover gasket and changed plugs. The read out is now 27 mpg .... and you can feel the difference.

They came pre-gapped at .53 .... and don't forget the anti seize for the aluminum

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Discussion Starter · #4 ·
The first set of plugs were gapped at 0.4 which is why I increased the gap and likely broke the plugs in the process. I didn't check the gap on the second set as I bought them at Lordco and the guy there said it's not necessary. I did use dielectric grease, the plugs stated not to use anti-seize with them.

How did you identify the valve cover leak and is that a DIY job?
 

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She will start to hesitate a little on acceleration when the gaskets let go. The coil area fills with oil. you can pull a coil pack and see if it is full of oil to see if it let go. The last one will usually fill first. Mine had three out of the 4 full. I pull the plug and let the oil go into the cylinder. Makes for quite a smoke show at start up.... you could probably figure a way to suck the oil out to prevent the smoke clouds.

If you see oil on the top ... it is usually a sign it has let go.

Pretty easy fix... bunch of UT videos that are great.


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Discussion Starter · #6 ·
Thanks, I just checked and there are no signs of oil. My pondering continues. Hopefully I get it fixed because otherwise it's such a great vehicle, but it should really be using less fuel than a truck.
 

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It's a 22 year old car that's gone through a few rough Canadian Winters I'd bet. Things just are not going to work like new, bearings are going to be stiff, suspension is going to be sloppy, engine is going to be loose. Friction, resistance, lower power than factory all are going to detract from fuel economy.
20mpg is pretty low. I would say if you can get to 25mpg you should be in a decent running spot (minimal idling to warm up time).

But weigh the cost of parts trying to get better MPG vs just leaving it be. Where is that point where the new parts save money.
 

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She will start to hesitate a little on acceleration when the gaskets let go. The coil area fills with oil. you can pull a coil pack and see if it is full of oil to see if it let go. The last one will usually fill first. Mine had three out of the 4 full. I pull the plug and let the oil go into the cylinder. Makes for quite a smoke show at start up.... you could probably figure a way to suck the oil out to prevent the smoke clouds.

If you see oil on the top ... it is usually a sign it has let go.

Pretty easy fix... bunch of UT videos that are great.


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Soak up with paper towels first. You can bend a connecting rod letting it drain into the cylinder. Not a good idea to let it drain into the engine.
 

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Discussion Starter · #9 ·
It's a Westcoast car, so rough Winters wouldn't be an issue. I'd be pretty happy with 25, as you say it's an old car. What really baffles me is that it went up with the new plugs only to drop after the one week of snow and cold. I definitely don't want to sink too much money into it but the break-even point is not too far at these gas prices.
 

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(If your still looking for some ideas on why you’re getting low fuel mileage) I have a 2001 wagon, i was getting 28-32 mpg (80% commuting miles 20% city miles) and then it just started getting worse out of no where. It slowly started dropping about 2 mpg every month (I drive 150 miles+ a day) . I got lucky a one day the check engine light came on and it was for the high pressure fuel sensor. I reset the check engine light and it never came on again. After researching it I found it can tank your fuel economy and many times you never get a check engine light (sometimes you have other symptoms but I didn’t). Had i bought the car after this i would have just thought it got low mpg. Once i replaced the sensor i was back up to my normal MPG. Might be something worth looking into.
 

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Like said do NOT let the oil run into engine; if it hydrolocks then likely you break or bend a rod when you next crank engine up. And, don't ask me how but you can get rocks in that oil and big enough to bash piston flats up. I airblow those pockets out and some of the trash will knock holes in your face. BTDT.
 
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