Low Gas Mileage

[etz bseder]

My car has been getting only between 13 and 15 miles to the gallon, and I have just been driving it as a normal person would in the city. I used to get much higher with all of my other cars and even a couple mpg higher a couple months ago.

I have a slightly modified exhaust and a cone filter, and a stage 1 ecutune. As far as I know, there are no leaks, and I am out of things to look at/for.

Any ideas what could be causing my very low mileage?

[ShiuludeSVX]

When your running at highway speeds, what are your RPM's?
If your running at over 2500rpm at 60, then you might be stuck in 3rd, with no 4th gear.

When you roll from a start, is the car quick to respond, or is it a bit sluggish?
If your slow to jump, then you may have lost 1st gear, and your dragging 3500 lbs until you get over 25mph.

What are your Cold, and Hot Idle RPM's?
If the hot idle is not coming down to about 700rpm then check the TPS, and MAF. High idle {over 1500} on a cold block is waisting fuel already.

My 2pennies.

Originally Posted by etz bseder

My car has been getting only between 13 and 15 miles to the gallon, and I have just been driving it as a normal person would in the city. I used to get much higher with all of my other cars and even a couple mpg higher a couple months ago.

I have a slightly modified exhaust and a cone filter, and a stage 1 ecutune. As far as I know, there are no leaks, and I am out of things to look at/for.

Any ideas what could be causing my very low mileage?

[ensteele]

Are you using regular or premium gas?

[NikFu S.]

Could just be season/temperature related. Sales stickers state a low of 14 should be expected under certain unstated circumstances.

[ShiuludeSVX]

Originally Posted by NikFu S.

Could just be season/temperature related. Sales stickers state a low of 14 should be expected under certain unstated circumstances.

I'm at the same elevation, and although it is not quite as cold here, the temperatures are being sustained pretty low.

I have noticed a bit of a change in my MPG, but only from 24 to 22mpg under normal driving.

I routinely will get almost 400 miles to a tank that I have only run dry one time. My total miles is about to go over 235000 now.

So, I would have to say there must be something else going on in this case.
Maybe the Octane, but I think it's more mechanical.

[etz bseder]

I deffinately use premium, but i'm in greeley, so who knows if it really is premium. My car doesn't have a high idle but does get close to 700 as a low hot idle. I have checked for codes and i do occasionally get a O2 sensor code, but that's it.

My car is never sluggish and i should have all gears. I just had my tranny rebuilt.

I'm really running out of ideas. I thought our cars were a bit more efficient than this. My car does have a rough start a lot but I have yet to track down what it is of find someone who could.

Any other ideas out there?

[STORMINORMAN]

...dirty fuel injectors, worn spark plugs, winter blend gas.

How many tankfulls? Who did the "ecutune, exhaust, cone filter"? Was it checked with an exhaust "sniffer"?

Cheers!

[etz bseder]

I'm not sure about the exhaust "sniffer" but i did the ecutune and cone filter. which would be the easiest/cheapest to replace out of fuel injectors and spark plugs. this is going on about 4 tankfulls

[STORMINORMAN]

...pull the frontmost (foremost?) (1st?) spark plug on the passenger side pretty easily and take a look at its condition.

The "sniffer" I'm referring to is an exhaust gas analyzer and it should tell you much more about your fuel mixture. I can't tell from this reply screen what year your SVX is: i.e., OBDII or not, OR what your State is: here in Oregon you can drive through the DEQ test station and find out if your car passes the emission tests.

I wouldn't go pulling or replacing fuel injectors without getting a little more info...

Cheers! & Good Luck!

[etz bseder]

Alright thanks.

It's a '92 and we (in CO) do have an emissions test required for registration

How hard is it to take out the spark plug? i've read that ours are hard to do because of the coil packs. I have replaced the ones in my old (RIP) legacy wagon, but it had a distributor

[NikFu S.]

Originally Posted by ShiuludeSVX

I'm at the same elevation, and although it is not quite as cold here, the temperatures are being sustained pretty low.

I have noticed a bit of a change in my MPG, but only from 24 to 22mpg under normal driving.

I routinely will get almost 400 miles to a tank that I have only run dry one time. My total miles is about to go over 235000 now.

So, I would have to say there must be something else going on in this case.
Maybe the Octane, but I think it's more mechanical.

Like I said, unstated ie unspecified conditions. If you are getting more than 20mpg you are doing a lot of long distance tc lock driving. "Normal" city mpg is 17. 14-15 should be expected during the winter.
I'm getting 13 and everything is running pretty tip top.

[dcarrb]

Originally Posted by NikFu S.

If you are getting more than 20mpg you are doing a lot of long distance tc lock driving. "Normal" city mpg is 17. 14-15 should be expected during the winter.

Sounds about right to me. I'm currently getting 17-19 mpg in daily driving (both cars), with the TC locking about the time I get where I'm going, mid-to-high 20s on the road, and I don't run 100% premium fuel. Overall average in the teal since I started keeping records a couple of summers ago is >21 mpg. Little doubt a consistently colder climate would dial those numbers downward.

dcb

[STORMINORMAN]

...on the passenger's side is pretty easy to access.

Remove/loosen the bolt holding the coil pack. GENTLY wiggle the coil pack from the spark plug end. Remove the plug just like any other plug. Inspect. Clean, regap, replace if needed. The hard part about replacing spark plugs is accessing the ones to the rear on both sides, usually removing the airbox and battery + tray gives one a lot more wiggle room. I always put a gob of dielectric on the end of the plug (or the coil pack end) to ease future efforts.

A '92 doesn't have OBDII. Find out if the CO DEQ (?) does their emissions testing for free or not. Changing the program/intake/exhaust can change your mixture. If you can find a shop with a sniffer that isn't charging $75 to hook up (which seems to be in vogue now-a-days) getting the readings may answer your questions (or bring up a couple more )...

I've gotten 28+ mpg AVERAGE on a crosscountry trip before: IMHO 13-14 mpg is pretty low UNLESS you are driving very aggressively almost all the time. We average 20 mpg in town running regular most of the time.

Cheers!

[ShiuludeSVX]

As an aside.

I got my SVX IN Littleton, and drove it the 1000 miles straight to Prescott, Az.
During the trip I got just over 27mpg the whole way down, and used regular unleaded fuel.

Since then I use additives to keep the injectors clean, and to try and pump up the Octane, since you can't get good stuff anywhere, but at the local Airport here.

I have logged EVERY gallon that has gone into this vehicle, and the mpg has never gone below 21.

A very good place to start would be to check the plugs {all of them if you can}.

[etz bseder]

Thanks a bunch. I'll try to check the plugs this weekend. I am going to be in littleton (if anyone would like to help). Hopefully it won't be too cold and snowy for me to be outside for awhile to check them.

Assuming that it is my plugs, are there any recomendations on where to go to get plugs, what plugs to get, or where to get them installed at?