1999 V6 Bad MPG

austin3749 · Dec 8, 2018

I have a '99 V6 that I purchased a few months ago. I never really cared much about the fuel economy of it or worried about it, but I'm putting in about $20 (7 gallons) to get myself UP TO like 80-100 miles, when in reality I should be getting closer to 160 or 180. I'm gonna be replacing the spark plugs with NGK G-Power, but I wanna note I don't have my cats on my car, it stops about halfway under the car at the...Y-Pipe? I don't believe the exhaust is causing an issue with the MPG, but if you guys think so, that would be nice. I plan to buy a dual exhaust converter kit when I get the money so I can pass inspection in December. Any ideas what else it could be?

wmburns · Dec 8, 2018

If this were my car I wouldn't spend a single un-necessary dime until I KNEW the base motor health is good. Stop. Do not pass go. Go straight to a Compression and leak down test.

Wouldn't hurt to rule out other basic stuff like dragging brakes.

OBTW, I routinely get 21 MPG in the city in my 2000 GT with the 4.6 V8

austin3749 · Dec 8, 2018

wmburns said:
If this were my car I wouldn't spend a single un-necessary dime until I KNEW the basis motor health is good. Stop. Do not pass go. Go straight to a Compression and leak down test.

Wouldn't hurt to rule out other basic stuff like dragging brakes.

OBTW, I routinely get 21 MPG in the city in my 2000 GT with the 4.6 V8

Well, regardless I should get spark plugs, fuel filter, etc anyways considering it's hitting 120k soon and it apparently hasnt had a tune up since around 80k, serpentine belts, etc are supposedly dry-cracked so...I'm slowly doing everything about MPG at this point. I don't believe it's dragging brakes, especially since my E-Brake doesn't work, *supposedly* since WD-40 got sprayed on it so the cable is probably loose. The thing's honestly cheap AF, I got it for $800 and had to fix the broken clutch for $600.

wmburns · Dec 9, 2018

Here's some information on something that could prove very useful in your quest to get this car "road ready". Good luck.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

austin3749 · Dec 9, 2018

wmburns said:
Here's some information on something that could prove very useful in your quest to get this car "road ready". Good luck.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

Thanks man. And also, after I got the car, I noticed it had a check engine light. I haven't gotten it checked out yet, but I assume it's because I have no O2 sensors for my cats which aren't existent on my car. I'm going to get it checked ASAP, and rather than make my car look and sound all nice, I'm gonna try to get it into working order from the previous stupidity that have owned it. Any other ideas that it might be besides the O2 sensors? I know it's a longshot to ask, but I'm wondering if there may be anything that's obvious to you and not to me.

wmburns · Dec 9, 2018

Don't guess. TEST!

Learning how to use an ODB2 scanner to actively trouble shoot a car will change how you think about trouble shooting forever.

Resist the urge to repair by "parts changing" unless there are no other options.

austin3749 · Dec 9, 2018

wmburns said:
Don't guess. TEST!

Learning how to use an ODB2 scanner to actively trouble shoot a car will change how you think about trouble shooting forever.

Resist the urge to repair by "parts changing" unless there are no other options.

Alright, sounds good. Thanks for the advice, I'll definitely look into it.

austin3749 · Dec 9, 2018

wmburns said:
Don't guess. TEST!

Learning how to use an ODB2 scanner to actively trouble shoot a car will change how you think about trouble shooting forever.

Resist the urge to repair by "parts changing" unless there are no other options.

Do you by any chance know where I can find a spreadsheet for new edges that contains all the information? Was looking around but seems to be trial-and-error for configurations, and I can't find a single place for mustangs older than 2010. It arrives Tuesday, so I hope by then I can find out any information that would help me make some configurations, but if not that's oh well.

wmburns · Dec 10, 2018

The list of available PID's is different for every model year and "application". Suggest that if you want a list of PID's to attach the ODB2 scanner and print the list of available PID's that come up.

Using the term "configurations" has me worried that you understand what an ODB2 scanner can and can't do. An ODB2 scanner is NOT a tuner. You can't use it to made "configuration" changes to your car.

There is limited "two way" activation available. For example:

activate cooling fan
activate EVAP purge bay test
KOEO tests
PATS (with enhanced software license).

The ODB2 scanner will give easy access to PID values. It's up to you to understand HOW to use effectively this information. Years of technical training can go into how this is done. Think of an ODB2 scanner as a diagnostic tool such as an X-ray. Some problems are easy to spot (major broken bones). Others not so.

austin3749 · Dec 10, 2018

wmburns said:
Don't guess. TEST!

Learning how to use an ODB2 scanner to actively trouble shoot a car will change how you think about trouble shooting forever.

Resist the urge to repair by "parts changing" unless there are no other options.

Hey, so quick question. If my ODB2 scanner notifies me that there's an O2 sensor, and let's say that my fuel is running too rich due to no cat converters, would I be able to disable my O2 sensors through ODB2 so it would be running at a normal air-to-fuel ratio? I know you're the expert here and I'm just a wanna-be 'stang modder, but I'm interested in whether that's possible.

austin3749 · Dec 10, 2018

wmburns said:
The list of available PID's is different for every model year and "application". Suggest that if you want a list of PID's to attach the ODB2 scanner and print the list of available PID's that come up.

Using the term "configurations" has me worried that you understand what an ODB2 scanner can and can't do. An ODB2 scanner is NOT a tuner. You can't use it to made "configuration" changes to your car.

There is limited "two way" activation available. For example:

activate cooling fan

activate EVAP purge bay test

KOEO tests

PATS (with enhanced software license).

The ODB2 scanner will give easy access to PID values. It's up to you to understand HOW to use effectively this information. Years of technical training can go into how this is done. Think of an ODB2 scanner as a diagnostic tool such as an X-ray. Some problems are easy to spot (major broken bones). Others not so.

Okay, thank you.

wmburns · Dec 10, 2018

austin3749 said:
Hey, so quick question. If my ODB2 scanner notifies me that there's an O2 sensor, and let's say that my fuel is running too rich due to no cat converters, would I be able to disable my O2 sensors through ODB2 so it would be running at a normal air-to-fuel ratio? .

Again. An ODB2 scanner is NOT a tuner. It allows for the MONITORING of operational data.

OBTW, in a modern car a missing cat would never cause the Air/fuel ratio to be off. For a 2004 or older Ford, the rear O2 sensors are used only to monitor the cats. Therefore a bad rear O2 sensor would not cause a driveability issue.

An ODB2 scanner would allow one graph operational data such as:

MAF air flow.
RPM's
Long term fuel trims (LTFT).
O2 switches.
fuel pressure
misfire data via ODB2 mode 6 data
and 1,000's more.

By comparing PID's to other PID's or by comparing to known good known good values it is possible to figure out what's wrong.

I recently fixed my Mustang with a bad O2 sensor (no DTC code being thrown). My scanner told me that the O2 sensor on one side NEVER switched even when forced rich. The O2 sensor on the other side was switching rich/lean normally This was causing the PCM to add fuel to one side only producing a misfire. This allowed me to replace the O2 sensors with the virtually certain knowledge the repair would solve the complaint.

Note2: it's unreasonable to expect to get software capable of "tuning" a car for the cost of a $35 USB adapter with "free" software.

austin3749 · Dec 10, 2018

wmburns said:
Again. An ODB2 scanner is NOT a tuner. It allows for the MONITORING of operational data.

OBTW, in a modern car a missing cat would never cause the Air/fuel ratio to be off. For a 2004 or older Ford, the rear O2 sensors are used only to monitor the cats. Therefore a bad rear O2 sensor would not cause a driveability issue.

An ODB2 scanner would allow one graph operational data such as:

MAF air flow.

RPM's

Long term fuel trims (LTFT).

O2 switches.

fuel pressure

misfire data via ODB2 mode 6 data

and 1,000's more.

By comparing PID's to other PID's or by comparing to known good known good values it is possible to figure out what's wrong.

I recently fixed my Mustang with a bad O2 sensor (no DTC code being thrown). My scanner told me that the O2 sensor on one side NEVER switched even when forced rich. The O2 sensor on the other side was switching rich/lean normally This was causing the PCM to add fuel to one side only producing a misfire. This allowed me to replace the O2 sensors with the virtually certain knowledge the repair would solve the complaint.

Note2: it's unreasonable to expect to get software capable of "tuning" a car for the cost of a $35 USB adapter with "free" software.

Yeah my bad, was just reading up on some things that weren't exactly the most accurate. Apologies for my ignorance, I'm not really mechanically that great, even though I would like to be. I suppose I'll see what happens tomorrow when I go ahead and check it out. I'll post something tomorrow afterschool on what it is.

1999 V6 Bad MPG

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