993 bad gas mileage

[CLB 993]

Hello All,

I'm a newbie here with a 1997 993 C2 that's getting 11 MPG in the city. The car seems to run fine with the exception of a recent P1411 CEL. I cleared the code and got some live data at idle and fully warmed up from my OBDII Reader for you guys to look at. As I don't know what the values mean and am not sure what the values should be, could any of you give me any thoughts as to what might look incorrect and what avenue to pursue in solving the rich condition?

In English Units:

Live Data

Numbers of DTCs 0

Fuel system 1 statusCL

Fuel System 2 statusCL

Calculated Load Value(%)1.2

Engine Coolant Temperature(¡£F)280

Short Term Fuel Trim -Bank 1(%)-0.8

Long Term Fuel Trim - Bank 1(%)-1.6

Short Term Fuel Trim -Bank 2(%)0.0

Long Term Fuel Trim - Bank 2(%)-0.8

Engine RPM(rpm) 771

Vehicle Speed Sensor(mph)0

Ignition Timing Advanece for #1 Cylinder(¡£)4.0

Intake Air Temperature(¡£F)95

Air Flow Rate from Mass Air Flow Sensor(lb/s)0.01

Absolute Throttle Position(%)0.0

Commanded Secondary Air StatusOFF

Location of Oxygen SensorsB1S12--B2S12--

Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.740

Short Term Fuel Trim Bank 1-Sensor 1(%)-1.6

Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.455

Short Term Fuel Trim Bank 1-Sensor 2(%)N/A

Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.690

Short Term Fuel Trim Bank 2-Sensor 1(%)-0.8

Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.625

Short Term Fuel Trim Bank 2-Sensor 2(%)99.2

Or in Metric:

Live Data

Numbers of DTCs 0

Fuel system 1 statusCL

Fuel System 2 statusCL

Calculated Load Value(%)1.2

Engine Coolant Temperature(¡£C)141

Short Term Fuel Trim -Bank 1(%)-0.8

Long Term Fuel Trim - Bank 1(%)-1.6

Short Term Fuel Trim -Bank 2(%)-1.6

Long Term Fuel Trim - Bank 2(%)-0.8

Engine RPM(rpm) 844

Vehicle Speed Sensor(km/h)0

Ignition Timing Advanece for #1 Cylinder(¡£)4.0

Intake Air Temperature(¡£C)35

Air Flow Rate from Mass Air Flow Sensor(g/s)5.69

Absolute Throttle Position(%)0.0

Commanded Secondary Air StatusOFF

Location of Oxygen SensorsB1S12--B2S12--

Oxygen Sensor Output Voltage Bank 1-Sensor 1(V)0.250

Short Term Fuel Trim Bank 1-Sensor 1(%)3.1

Oxygen Sensor Output Voltage Bank 1-Sensor 2(V)0.580

Short Term Fuel Trim Bank 1-Sensor 2(%)N/A

Oxygen Sensor Output Voltage Bank 2-Sensor 1(V)0.735

Short Term Fuel Trim Bank 2-Sensor 1(%)-1.6

Oxygen Sensor Output Voltage Bank 2-Sensor 2(V)0.615

Short Term Fuel Trim Bank 2-Sensor 2(%)99.2

----------------------

Thanks,

Craig

[White987S]

Depending how strong your right calf muscle is, that's not aweful city MPG's. What's your highway MGP's? Post this question on Rennlist too. Ton's of 993 activity overthere.

The P1411 code is most likely related to your SAI system. You need to research this more. Common concern on the 96-98 993's.

Edited May 9, 2014 by White987S

[CLB 993]

Thanks for the reply White987S. That's the deal...I'm driving very moderately to see if I can get better gas mileage. Also to clarify, that is more of a combined route back and forth to work...some rural and some urban. My other daily driver (2011 F150 V8 5.0) gets about 17 MPG on the same route. I haven't taken the 993 out on the highway for any stretch to see what HWY MPG's are like.

Does anything on the OBDII Scanner printout jump out at you?

I'll try this on Rennlist also...

Craig

[CLB 993]

Well here's an update. If any of you are like me...I like to hear what the "fix" turned out to be.

After not getting much feedback about the values from the OBD reader, I just started doing some common sense investigation.

My car runs fine. I don't have any black soot around the rear of my car. I don't smell fuel when it's idling in the garage or when I park it in the garage after a good 30 minute drive. It's not running rich at all.

I thought it must be something else. I started measuring on a mapping program the exact distance I travel to and from work and started checking my trip meter and odometer to see if they match the distances. They don't! My odometer/trip meter have an intermittent error. I noticed this morning several miles into my commute that the trip meter/odometer didn't move from when I left home. I just barely touched the trip reset push pin and it started working again. But on the commute home there were times where it did not log the mileage again.

I knew it was running really well so, no worries...just drive it like it is!

[binger]

Two common issues with the 993. Your P1411 common Secondary air injection fault code on cylinders 4-6. The passages get blocked from coking buildup. Your speedometer is another common issue where the small gear inside deteriorates over time and breaks. Sometimes it will be intermittent but will fail soon. We use

North Hollywood Speedometer for that fix. Hope this helps.

http://nhspeedometer.com/911/service_restorations/1.htm

[CLB 993]

Thanks Binger. Right on about the odometer. Yesterday it did not clock any mileage for a few miles and then on its own it started clocking mileage. At this point it is intermittent but I too suspect it will fail soon. At least the speedo works.

[binger]

If your up to it there is a DIY for the fix.

Part ->>>>> http://www.odometergears.com/products/Porsche/911-993+94-98/72

[CLB 993]

So, now it's a question of what tooth count gear I have. I guess I'll have to take it apart and see which it is before I can order the gears.