11 miles per gallon!!?

[BerniniCaCO3]

I'll be trying to pull OBD1 codes for the first time myself, soon So following this with some interest.

It'll be hilarious if these newer, gizmo-filled cars were enabled with wi-fi and send you an email at work when your car throws an error code while your son's driving it!
Then follow illustrations of the probable cause in high-res to your inbox, and advertisers can pay to give you annoying, flashing animated quotes to do the repair. "we heard Mr Arnest that you recently had a check engine light, let us fix it for less!"

Goofiness aside, I'll second that hills kill gas mileage; I drove down skyline drive last month and got nothing like the 25mpg I was getting on the flat beltway in baltimore! Nothing at all like it

I am also curious: i was reading up on O2 sensors (I replaced one of them for 'shits and giggles' already, where is the second one however...? The one I changed was right off the driver side exhaust beneath the spark plugs).
I read that they only function at 600F. Now of course, the overall engine temperature is 195F, if the cooling system and thermostat do their jobs! And it takes my car at least 5 minutes to get up to full temperature. But how long does it take for the exhaust only to get to 600F? And can I presume that until it does heat up, the O2 sensor is for all intents and purposes inactive and your fuel economy will be hell?

[91waggin]

1. O2 sensors are located in the left and right side exhaust manifolds.

2. Overall engine temperature is not 195F. "Overall engine temp" is not a meaningful or useful measurement, simply because stuff in the engine is all at different temps. The thermostat opens at 195F, which means that the engine coolant will stay around that temperature. I do not know about the truth of the 600 degree number for oxygen sensors, but what I do know is that after the engine has reached operating temperature, or the engine has been running for 10 minutes, the computer enters "closed loop" mode, meaning that it starts paying attention to all of its sensors (including O2) and fiddling with the fuel mixture on a finer scale.

3. Most of the mixture decisions in Ford's EEC-IV system are made by the Manifold Absolute Pressure sensor, the Engine Coolant Temp sensor, and the Intake Air Temp sensor. Once the computer has entered closed loop mode, it starts paying attention to the oxygen sensors, which it uses only to fine-tune the fuel mixture for best possible performance. On newer cars, the computer pays far more attention to O2 sensors than it does on EEC-IV.

tl;dr version:
The O2 sensors in our cars only fine-tune the mixture. This means that your fuel economy probably won't be shit until the exhaust gets hot, but it won't be as good as it could be.

[HATNINJA]

hey bernie you dont have obdI on your car its EEC-IV. i could be wrong here but i think an obd1 wont pull codes from an EEC-IV im not sure though but i do know that your system is an EEC-IV.

[Lincolnmania]

i live in the mountains and i get about 16 mpg with a HO......check for vacuum leaks

[BerniniCaCO3]

so this guy is not the correct tool?
http://www.autozone.com/autozone/acc...fier=2396_0_0_

[BerniniCaCO3]

I figure if the coolant is 195F, then the cast iron block, which is a nice heat sink, ought to be 195 too. But even that I suppose doesn't mean much

The 10 minute mark means more. If one gets say in the low 20s mpg cruising on the highway, and maybe 18mpg around town (going 30-40mph between stoplights-- not stuck in traffic), what sort of fuel economy, back of the envelope sort of guesstimation, can I expect on that 10minute trip to the 7-eleven for a jug of milk? When the car never has time to warm up properly?

[sly]

that is the same tester I have. If you don't have the book any more I can scan the KOER testing pages for you.

as for the short trip driving... expect 10-14 mpg depending on just how rich the open loop running is.

[gadget73]

so this guy is not the correct tool?
http://www.autozone.com/autozone/acc...fier=2396_0_0_

it will work, but its $30 for exactly the same thing you can do with a piece of wire and maybe a test light. I'm cheap. If I'm spending 30 bucks, I want a digital display, not a light I have to watch. I can get those results for 5 bucks or less. If your car has the amber "check engine" light, you can sit comfortably in the driver's seat and count off the code blinks. If it doesn't, then you'll need to stand outside with a test light and watch it.

http://fordfuelinjection.com/?p=13

[91waggin]

It'll work, but it's a waste of money. You can do a few different cheaper things. If you have a yellow "check engine" light (89-up vehicles), you can do this:

then count flashes of the check engine light.
If not, you can put a 12v test light in place of the jumper wire and count flashes of the test light.

[HATNINJA]

yeah

i live in the mountains and i get about 16 mpg with a HO......check for vacuum leaks

ill check for leaks. the car runs so good though except for me having to raise the idle because it wouldnt run with a/c on in gear. gonna pull codes too. the thing that gets me is i see most people getting the mileage you quoted and im like shit!

[91waggin]

What is the rear end in your car? If I do a tank with all city driving, I'll get 11-12 miles to the gallon. I rarely see what most people in this forum are getting. I have a 3.08 rear end and I think that if I had a shorter rear end I might get better city mileage simply because I don't have to tromp down quite so hard on the gas pedal in order to get moving.

[87gtVIC]

What is the rear end in your car? If I do a tank with all city driving, I'll get 11-12 miles to the gallon. I rarely see what most people in this forum are getting. I have a 3.08 rear end and I think that if I had a shorter rear end I might get better city mileage simply because I don't have to tromp down quite so hard on the gas pedal in order to get moving.

that is what I get around town with my 3.08's.

[BerniniCaCO3]

What is the stock rear differential on a 1990 grand marq wagon? I honestly don't know what I have-- but it's safe to assume the previous owner never swapped anything.

I was also wondering: I have a friend with a 1999 ford ranger that's getting 16mpg mixed. It might have a bad O2 sensor, we just switched it... but fact is it's never going to get more than 19. Any possibilities for a different gear ratio there, to improve fuel economy on the highway? Most of the driving is highway, not city; so I guess re-gear it for less low-end torque, but lower engine rpms at higher speeds if I understand this correctly.

[BerniniCaCO3]

I don't have a check engine light on, but my understanding is that I can pull the codes anyway? I want to find out why it stalled a couple weeks ago.

Well, I already have the actron anyway... and the book, of course. But now that I know I'll pass word to any friends with pre-obdii cars not to spend the money.

[HATNINJA]

thats correct if it has codes stored it dont mean the light has to be on. but the light did come on when the code was stored even if momentarily (sp) this would be called an intermitent code. if the light remains on i call it a hard code.