Gas Question

[matty]

hey everyone was qurious of something on my 89 im getting about 160 miles per tank.good or bad?just did wires plugs valve cover gaskets etc,etc its just i thought my 91 was about 240 a tank but cant remember need new motor for that one.

 

[JoesSHO]

O2 sensors are probably junk... Exact symptom

 

[mclarida]

O2 sensors are probably junk... Exact symptom

Plus-The 93 octane burns slower and has a better timing curve=more power and better mileage. Not a huge diff. but there is a diff.
M

 

[seraphiem]

When I brought my first SHO home I was getting about 8 - 10 mpg which sounds about the same as your 160 miles to tank.

Find out what your mpg figure is then you can draw comparsions with others on the forum here.

Things to check that caused this really bad mileage on my car.

#1 Dead O2 sensors.

Just replace them. 30 mins of work and $100 in parts will net you a great return.

#2 Stuck rear brakes. Due to seized sliding caliper pins and/or collapsed rear brake lines.

After a drive check your rear rotors by putting your hands near them. If there really hot there stuck. Or stop your car on an incline and see if it rolls.

I had stuck rear caliper pins which require pulling them out, cleaning them and a new application of grease. Or you can buy a kit with new pins.

I also had collapsed rear brake lines. Stepping on the brakes gets pressurized fluid to the caliper but the hose wouldn't allow a return of the fluid. New brake hoses are cheap but have a good torch and a flare wrench as those fittings will not want to come off.

#3 Engine Coolant Temperature Sensor ECT

This starts reading incorrectly over time and may mistakenly read lower temperatures. This results in your car running richer and sucking down more gas.

 

[matty]

thanks

thanks all that spoke ill go and check all those things

 

[Storm-Chaser]

matty
Don't go changing the oxygen sensors just because you're getting bad gas mileage. There are a number of things that can result in poor mileage, and your simply changing the plugs and wires with no resulting change in mileage is a good example of this.

If it is the oxygen sensors, they will be throwing codes that will be stored in the PCM's memory. Have you pulled codes? Have you done a "tail-pipe" check (ie. look at the color of the inner surface of the exhaust pipe)? Black indicates a rich-running condition. What color were the plugs? They too will tell you how the engine is running.

For what you've already spent on the plugs and wires, you could have had a low-level diagnostic scan run, which would have told you if the plug wires were bad, or one or more plugs are not firing properly.


Some "other" problems that can result in reduced mileage:

1. Is the gas guage working correctly? If it's reading incorrectly and your not doing actual mileage checks (miles driven divided by gallons used), you may be filling-up thinking the tank is empty, when it's actually at a half-tank.
   
   
2. Is the odometer reading correctly? If not, you may be driving more miles than you think.
   
   
3. Are you running stock tires (215-60 R16), or aftermarket low-profile rims and tires? Changing to non-stock profiles will affect overall gas mileage, as well as odometer mileage. How much is dependent upon how large the difference is in tire diameters.
   
   
4. How often are you checking tire pressure? Seemingly small drops in tire pressure will have an affect on mileage.
   
   
5. How does the car idle? Malfunctioning IACs and MAFs both can affect mileage, if they're affecting idle speed or incorrectly reporting air-volume entering the engine - which affects the oxygen sensors ability to properly adjust air/fuel ratios.
   
   
6. How is the car [engine] running? You may have clogged catalytic converters which will absolutely **** your mileage.
   
   
7. In addition to dragging brakes, what is the mechanical condition of the car? Wheel bearings, alignment, and clutch are some items that will affect mileage. Just as a dragging brake will decrease mileage, so will a badly worn/loose wheel bearings, as they increase rolling-resistance. A slipping clutch means you're not getting all the power to the wheels.

And these do not take into account your driving habits.

• Have you recently modded the motor modded in any way?
  
  
• Is the driving primarily in-city or highway-only driving?
  
  
• How often and how much do you have your foot-in-it?
  
  
• Have you been leave the car idling with a A/C running?

So, check the SHO over real well and look for other problems like running hotter-than-normal, how it idles, etc. Pull the codes and see what shows-up, then start there first.