New member with questions

[zcarguy]

I'm new to the Mustang scene but not new to cars in general so please feel free to use technical jargon.
I did search but didn't find the exact answers I'm looking for so please forgive me if these have been asked a thousand times.

I just bought a 93 5.0 LX convertible with only 65K miles and have a few questions about how these cars normally behave.

The car is totally stock (as far as I can tell) except for dual 2 1/2" exhaust with turbo mufflers. The CATS have been removed.

1. I took a relatively long highway trip weekend before last. The ambient air temp in the area I traveled through was around 106 degrees. The temp gauge in the car started out reading right in the middle but once I got on the highway steadily climbed to the 3/4 mark and stayed there regardless of what I did. I ran the A/C for a while and it didn't seem to affect the operating temp of the engine. Is this normal for these cars? I thought it seemed a bit hot.

2. The speedometer/odometer seems to read around 10%-15% low. Again is this normal error for these cars or has someone replaced the rear gears with a lower ratio. Is the ring gear stamped with it's ratio or do I need to count driveshaft revs to determine the ratio. I'd rather not open the diff housing but if it's stamped I'd know exactly what the ratio is and get a chance to change the fluid.

3. I seem to be getting about 15 MPG around town, is this low? I have an AOD so I understand the MPG will be lower than a manual but it seems a bit low. I ran the KOEO and KOER tests and got all 1s and ran the cylinder test and got a 9 so all tests passed. Will the codes show a bad O2 sensor or could the sensor(s) be bad and not throw a code.

Thanks in advance for any answers advice you guys give and I have to say this is one of the better car sites I've visited. Not a lot of flaming and arguing about stupid things.

ZcarGuy

 

[HISSIN50]

1. Every gauge seems to read differently. I'd get a real gauge so you know what is really going on.

When running hotter at speed (if you actually are), making sure the air dam is present helps. Otherwise it can be a heat rejection issue under load. A real gauge is needed for diagnostics.

2. the DS to wheel rotation method works pretty well. Then check the speedo gear you have and compare it to the charts (like D&D has - I havent memorized the gears as some have).

3. Some guys get better milage than others. I get about the same as you do around town. The EEC IV isnt real precise with sensory monitoring (in terms of finding skewed input or miscalibrated sensors). You can check HEGO function with a DMM (check for switching frequency and amplitude from 0.1 to 0.9 volts).

The same is true of the ECT and ACT sensors. Unless the sensor totally takes a lick, it might read within absolute parameters, but be totally out of calibration. You can ohm them out with the Chart Jrichker posts (or check the graph in Probst).

Congrats on the new ride and welcome to the site!


Good luck.

 

[poneypower89]

Also, if your gears have in fact been changed... then ur speedo/odo will be off.. and therefore so will ur reading on the gas mileage.

So, make sure your rear has the proper gear.. then worry about the gas mileage aftwards. Cool?