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SCPOC/Probe GT Member
Joined
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71 Posts
Discussion Starter #1
I only get about 23 mpg highway, and 21 city. For a 5-speed I
think that's pretty shitty. 3 years ago I could get 28
highway.
I don't get any codes, but my plugs, wires and O2 sensors
are 3 years old. But I don't really think that's a big deal.
If there's no codes, the sensors are fine, right? I do run more
negative camber and toe-out than most people, but not enough to destroy the tires or anything. Also the front brakes do rub a little if you take the wheel and turn it with your hands, because they are warped a little. But I can't
see all that taking away 5 mpg, do you? What do you think, I'm no engine ace. What are the most common causes.
 

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Probe GT Member
Joined
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23 Posts
One hypothesis:

As the O2 sensors age, the voltage output drops off ever so slightly. Not enought to light a code, mind you, but enough to make the mixture appear more lean than it actually is. The ECU compensates by enriching the mixture. You lose HP and MPG by running extra rich.

I think this exists on my own Probe; the HP is down, the A/F ratio is extremely rich past 3000 rpm or so, and the MPG stays around 20. New plugs, new wires, new cap, check & reset timing has no effect on (my) milage. But I'm not ready to change the O2's yet.

Good Luck
 

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SCPOC/Probe GT Member
Joined
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71 Posts
Discussion Starter #3
Yeah, I used to be able to get 425 miles on a long trip, now I can only get 350. New wires didn't change this. I do suspect I'm running rich though, because at my last emissions test it was discovered that my hydrocarbon reading was almost over the limit.
 

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Probe GT Member
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135 Posts
i use to get good mileige to!
and i have new highflow cat - new 02's - new air filter[cone] - basically everything that causes problems with gas miliege,

i got bad camber,? does this cause bad gas miliege?
 

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SCPOC/Probe GT Member
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71 Posts
Discussion Starter #5
maybe.....although I think bad toe would be more of a drag than bad camber....but I don't really know.
 

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Probe SE driver
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99 Posts
Maybe you guys just need to try cleaning your O2's with some carb/choke cleaner.
 

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Probe GT Member
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11 Posts
Another theory

It could also be that you have been getting some bad gasoline. Also, in some areas, they use different blends of gasoline depending upon the season. I dunno. But I tell you what, 23mpg is what I get with my ATX and I'm thrilled.
 

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SCPOC/Probe GT Member
Joined
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71 Posts
Discussion Starter #8
I use the same brand, Chevron Premium, as much as possible. And I've decarboned my engine a couple times. Still I can never achieve the 400-425 miles I used to be able to get 3 years ago.
 

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Probe GT Member
Joined
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23 Posts
PSE driver said:
Maybe you guys just need to try cleaning your O2's with some carb/choke cleaner.
Have you had good luck with this?

I had considered doing just that. I have heard that some cleaners are better than others, and some flat out damage the sensors.

Perhaps you could go into more detail, yes?
 

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Probe GT Member
Joined
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11 Posts
Read the Label :)

Go to your local auto parts store and check out the carb cleaners. The ones that are o2 sensor safe will say as much on the can.
 

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"oh, you were racing?"
Joined
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118 Posts
I've also heard of cleaning them with a propane torch. I guess it removes all the carbon build up from the sensor. Never tried it though.

On a side note. I used to get 32mph highway in my PGT. Since it's been back from the shop(and the timing has been corrected) I have lost at least 1mpg. But I also have a bad CKPS, and I think that it's giving me problems. :shrug:
 
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