Thread: gas mileage is turrible. can anybody help with clues?

0 knock retard. scanned a couple times to make sure. never given an issue yet. i did quite a bit of research before i took the chance on it. there were several people on here running 3.4 without headers or plog. there was also a grand prix website other than this that laid out the modding steps and on their 3.4 setup only the ubend delete was necessary. i wonder, with some people having trouble on the 3.4 setup if they have other issues with the car, like they aren't running the right plugs or something. that might be too simple but i ran it once with stock grade plugs and it was worse than the 3.8 and i thought it was going to screw up. the 104s were in some mod requirement lists i came across but i had never changed plugs before by myself so i hoped to not have to. but it turned out to be easier than i thought. i didn't think you could reach them from the top but you can.

It had more to do with the tolerances that GM has, iirc zzp noticed that on some cars the head gaskets hung over into the combustion chamber and that little bit of gasket caused the car to have kr. Some cars flow better from the factory than others do as well again do to GMs tolerances.
On my black car I had headers, ported blower, 104s, and open cone intake on a 3.5 and I still had kr.

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To be honest Zzp tunes dump fuel so that could be an issue

Yup dump fuel to kill kr.

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i drove the car for a couple months before i swapped pulleys and changed the pcm. fuel mileage dropped a bit as zzp said it would. but it has gone WAY down even from that point in the last month or so.

i have history on the setup. it got better than 13 mpg even when i drove it hard prior to this issue. but as i posted above changing the plugs helped get back to the normal performance. in the next few days i hope to clean the MAF and i've come across some posters suggesting cleaning the throttle body so i'll pull that off and look at it as well.

does anyone know off hand what size the torx head is for the MAF sensor? i gotta buy one for that.

thanks for all your help everyone

Originally Posted by Fivefingerdeathpunch

Maf sensor just has 2 screws holding it in place, they are torx style bits.

Not meaning to nitpick, but he'll need security torx, rather than regular torx bits, if he decides to do this. Failing that, he can always redneck it and cut some slots in the screws.

Originally Posted by GTP131

Not meaning to nitpick, but he'll need security torx, rather than regular torx bits, if he decides to do this. Failing that, he can always redneck it and cut some slots in the screws.

do you know what size?

Originally Posted by Jeff Murray

Do you get any knock with that setup? Seems like most people have more exhaust mods to support a 3.4 pulley. Not trying to criticize, just curious. I know every motor reacts differently to mods. Sounds like new plugs was a good call.

Originally Posted by Shiftingshaddow

0 knock retard. scanned a couple times to make sure. never given an issue yet. i did quite a bit of research before i took the chance on it. there were several people on here running 3.4 without headers or plog. there was also a grand prix website other than this that laid out the modding steps and on their 3.4 setup only the ubend delete was necessary. i wonder, with some people having trouble on the 3.4 setup if they have other issues with the car, like they aren't running the right plugs or something. that might be too simple but i ran it once with stock grade plugs and it was worse than the 3.8 and i thought it was going to screw up. the 104s were in some mod requirement lists i came across but i had never changed plugs before by myself so i hoped to not have to. but it turned out to be easier than i thought. i didn't think you could reach them from the top but you can.

My wife pulled up the computer and saw my reply to your post about knock retard and she says to me "Did you mean to call that guy a retard?" Funny. So she got a lil lesson.

people have literally been offended by the "knock retard" line before. one guys like i didnt come here to be called names lol

Yeah why you got to be calling people retards.

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Originally Posted by Slick2500

Yeah why you got to be calling people retards.
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It causes me a lot of problems. I just can't help it. But its more sensitive than calling people mongoloids.

Originally Posted by thekidinbuff

I do believe it is a T20 security bit

hey thanks. hopefully i can buy just the one at the parts store.

On a similar note my wife's GP was averaging pretty tuuuuurrrrrrrrrible fuel economy as well. Here were my findings:

FPR leaking...big surprise. Gained 2.1 mpg
O2 sensor was built by people with very little hands...aka cheap Chinese crap. Denso O2 gained me another 1.2 mpg
KR through the roof...amazing on a L36...but it happened. Replaced front knock sensor and amazingly it went away Gained me yet another 1.7 mpg
Spark plugs...previous owner "lets put some new cheapo Autolites in there"...WRONG. Put AC Delco iridiums back in and gained another 1.9 mpg

So, we started averaging 24 mpg highway and it's currently up to 31.9 mpg. Amazing what dumb little things will do.

Originally Posted by Sven The Sexman

On a similar note my wife's GP was averaging pretty tuuuuurrrrrrrrrible fuel economy as well. Here were my findings:

FPR leaking...big surprise. Gained 2.1 mpg
O2 sensor was built by people with very little hands...aka cheap Chinese crap. Denso O2 gained me another 1.2 mpg
KR through the roof...amazing on a L36...but it happened. Replaced front knock sensor and amazingly it went away Gained me yet another 1.7 mpg
Spark plugs...previous owner "lets put some new cheapo Autolites in there"...WRONG. Put AC Delco iridiums back in and gained another 1.9 mpg

So, we started averaging 24 mpg highway and it's currently up to 31.9 mpg. Amazing what dumb little things will do.

Man, dats turrrriiible.
i have thought about replacing 02 sensor as well. There are some things i'm learning along the way. You see, I thought when the car starts running like crap, getting really awful gas mileage, there would be some engine code to indicate that something is wrong and one might get some clues. this is proving to not be the case, however, and it can be sort of a witch hunt.

Originally Posted by thekidinbuff

I went to Advanced and for some reason they sold the non security bit ones separately but not the security bits. You have to buy them as a set.. at least at my store you have to. I ended up using pliers to unscrew mine lol

i didn't find any at all at advance. i was thinking of hitting an oreilly. walmart didn't have any sets even. ace might. but if it comes off with a pliers i'll just try that.

Originally Posted by HighOctaneRacing

Burn the ZZP PCM...

i still have the stock one. but i have no way to tune it, i don't know anyone that can tune it, and i think i shouldn't spend money tuning a basic setup like that. if i dragged it ever, i would want to go deeper on mods to where it would require a custom tune.

now, if i had a way to tune it myself and i could learn a lot doing so it would be worth it to me to try.

your in KS, go see reptile. hes your local tuner.

Originally Posted by Scottydoggs

your in KS, go see reptile. hes your local tuner.

how much monopoly money will he take?

hes still selling caned tunes, you'll have to pm for his in car tunes price.

this guy. http://www.grandprixforums.net/threa...s-98-02-GT-GTP