Big drop in mileage

[southtj]

Since mid July my CEL has been coming on occasionally. It would only stay on for a few driving cycles then stay off for awhile. During this time my mileage dropped about 1 mpg to about 14.5. This has occurred for the last 4-5 fill ups. The code I got is P0122 for the throttle position sensor.

My last fill up I decided to put in 93 octane just for the fun of it. The CEL never came on that tank full and also didn't have the hesitation that sometimes occurred when the light was on. When I filled up again and checked the mileage for that tank it was 9 mpg. :shock:

So, is the TPS causing problems even though the light isn't on or does my Jeep just not like the high octane?

If it is the TPS do you think it will have to be replaced?

 

[phall92139]

The Throttle Position Sensor is simple to change, did mine when I got the same diagnostic code as you. This is a pretty common failure. I found one at RockAuto.com. for between $30-$43 depending on which brand/model you choose.

93 Octane is not required in your Jeep and will provide no other benefit other than more profit for the Oil Companies. Fuel-injected engines like in our Jeep are designed to burn 87 Octane. Running a higher octane can send unburned fuel into the emissions system. According to this article, WHAT OCTANE RATING OF GASOLINE SHOULD I USE (What Octane Rating of Gasoline Should I Use?), it can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly.

I don't know how to account for such a drastic mileage drop. I didn't experience this as a result of the bad TPS and don't know if the higher octane gas could cause it either. Hopefully someone else will jump in here with a better answer.

 

[SteelHeadz]

I'm with Phill. The TPS should affect more so of the throttle response or stumbles. The drastic drop on fuel economy could be something else. I would just start with the basics such as tune-up, t.body clean and fuel injection cleaning.

 

[phall92139]

Sorry, can't help myself...just a quick hihack...

Confucious says: Don't eat the snow where the huskies go!

http://www.youtube.com/v/CmVvgo1wxh...lor1=0x2b405b&color2=0x6b8ab6"></param><param

 

[southtj]

I'm with Phill. The TPS should affect more so of the throttle response or stumbles. The drastic drop on fuel economy could be something else. I would just start with the basics such as tune-up, t.body clean and fuel injection cleaning.

I guess I'll give it another tank and see what happens then start with the cleaning etc.

 

[sndz03]

I am having the exact same problem with my in-line 6 - 2003 TJ - original owner - since May after a full spark plug and stock air filter replacement ; ( My fuel mileage had been consistent @ between 14.5 - 16 until then. Now it is all over the mpg map, in the mid 9 mpg and sometimes low 15 mpg ( which gets me real excited! ) nothing consistent...I have cleaned the throttle body but not the injectors, that will be next. Any other suggestions? I need to get this fixed, especially with the higher fuel prices. thx...sandy

 

[southtj]

Hey Sandy, welcome to Jeepz! Mine actually turned out to be a problem between the seat and the steering wheel. I had changed the battery during that tank and it had changed my trip odometer so the mileage was off. Now I'm back consistently 14-15.

What type of driving to you do? City/Hwy?

 

[JPNinPA]

Some may already know, but you have to be sure you go from full tank to empty every time to be sure you clocking the MPG correctly. I got measurement all over the place when I first would fill it go a day 60 mi and refill go another day 80 mi refill go 3 days 140 mi... the numbers were all over.

Other than this SNDZ03 the plugs you put in. What type, what did you gap them to and have you pulled them since to see what they look like?

 

[SteelHeadz]

It would be a miracle if i ever get 10mpg or better on my CJ. 8-9 mpg tops.
Thanks Phil, lol.