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Gas Milage w/ PI head swap

991 views 10 replies 7 participants last post by  krazy3o4 
#1 ·
I'm trying to see what other people that have done the complete PI swap (Heads/Cams/Intake) are getting.

I have done the full PI swap(Heads/Cams/Intake)
Marauder T/C
'02 GT MAF w/ air tube
3.27 posi rear
Rebuilt Trans (300miles now on it)
Performance Lonnie Tune
- 180* t-stat
- 12C plugs


I don't think my gas milage is very good.

I'm having a miss problem that I posted about in another thread. [That might have something to do with this.]
I already replaced the fuel filter, air filter is brand new, PCV valve is new, new plugs.

Car has 113,000 on it but only 300miles since PI swap and tune.
No codes.
Ran like a beast with great gas milage before all of this.
 
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#2 ·
My previous setup was identical to yours (except 3.55 gears) and I got 25 mpg on the highway.
 
#4 ·
well first of all, fix your miss....no sense in speculating about your crappy gas mileage until you fix it

with that setup you should be getting anywhere from 14-20 mpg city, and at least 25-27 mpg hwy....once everything is up to par

you could easily be off by a tooth on a cam sprocket and be out of time on the chains....done a compression check?
 
#7 ·
Same here, my gas mileage is not impressive either after the performance tune no matter how much I baby it. Stock tune gets me about 1~2MPG more so far in the city. Highway seems to do about the same to 1MPG more with the tune, haven't had it much on the highway to confirm, buts its definately not 25+ like some people are getting. Performance tune gave a bit more midrange power and fixed the shift points, otherwise it ain't doing for me either.
 
#8 · (Edited)
For the miss ....


Im guessing you need new sparkplug wires if you didnt change em yet .
 
#9 ·
I'd think O2 sensors actually, they do get worn out and if they are the factory ones they are almost 10 years old. I've never had wires give me any difference fuel economy wise.
 
#10 ·
So it was the wires ?
 
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