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Still getting HORRIBLE fuel mileage please help me

99GPGTP said:
Stock pcm back in. Drove 12 miles so far. Wot both stft and ltft go to 0.0
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I would drive it for a couple days before you reach any conclusions. They say it typically takes 20-30 minutes for them to learn, bit you have to consider all the different cells in the table. I've drove for a week and still had cells that weren't touched. Of course you will get a good idea in your situation sooner, I'm just saying for best results you gotta be patient.
 


99GPGTP said:
22-24 was actually combined city /hwy. Straight city was 19-22 depending on how i drove. Currently at idle my
ltft is -8 to -13 fluctuating little
Stft is -1 to 4 fluctuating little
Ect 204*
Map 6.4psi
Tp.45volts
Maf frequency 2691hz.
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In both of my GTPs my combined mileage was about 22 mpgs 16-19 city and 26-30 on the highway. That was even with a few bolt ons and a heavy right foot mod.
 


i to get on interstate and drive with cruise on at 75-80mph and always got 28-30mpg. the best ever was 32 but that was with a bottle of nos octane booster. now i cant get but 19.8 is my best. thats calculated from filling up and driving 125 miles on interstate and filing up again and diving miles by amount it took to fill up.

is it possible that the computer cant adjust for the extra fuel the fuel pump is supplying. i have tried comparing my fuel pressure to my co workers 2000 gtp and mine is 10psi higher when i rev it compared to hers.
 
Drove car for another 10 miles then let sit for 5 min off. Drove 10 more and repeated. Car now at idle has stft 0.
Ltft -11 at idle

While at half throttle on accel its stft 0 ltdt -9

Wot 0 stft
-7 ltft
 
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sounds like a stock tune now. they run em rich like that.

seems like your engine dont like the zzp tune much.

leave the stock pcm in for a few days. keep a eye on the trims, as they maybe still learning. see if they change further during the week.
 
can you explain this then?

2 months ago i had the car exactly the way it in right now. stock fpr, stock computer and all other mods. was driving back and forth to my g/f's house at that time 52 miles away. car still got best of 19.8mpg running cruise control 90% of the time and half that trip at 70 mph. the other half at 60mph cruise set
 
your car hates the tune. all zzp does is set a PE tune, its called power enrichment. you play with that file and it changes the trims big time, not always for the best.

i read a locals regal here, its a 98 like mine, so i took his pe file aka a zzp 1.0 tune, and my car hated it. trims went + at wot and it had a few degrees of kr.

so i made my own pe file took 5 adjustments to get it where the engine was happy. i pretty much ending up was scaling back the zzp settings 1/2 way back to stock number. then adjusted the injectors to fine tune the trims. so far so good.
 


I did a test when i had the adj fpr and i lowered the fp till i got 0.0 on both trims. Ended up at like 42psi at idle but car didn't like it that low.
 
you want it to be a little rich like -5. to -3 when driving, for idle even is good for the ltft. this way when you mash the gas it dont lean out on you.
 


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