3800 Horrible Gas Mileage #2

[Mikes1998GTP]

I can only wish that I was getting gas mileage of 18MPG like "frankenstinesy" posted earlier on this forum. As you can see from the picture, this is terrible!! I've yet to hear back from Charles at DHP about doing a PCM flash for me at MOD day, will anyone else at the Mod day be able to do flashing for a 1998 GTP? That AFC 2.0 sounds good, I'd love to fine tune mine to get mileage like that. I have an Intense 180F thermostat, but it doesn't seem to be doing its job. I've recently replaced the plugs as we found those were bad, the plug wires are fine, I'm thinking either PCM or new fuel filter next... any suggestions beyond that?

Thanks in advance... --Mike

Click to read more...

 

[Fish]

You sure you have a 180 thermo?? Mine barely gets over the second line sitting in traffic.

 

[Mikes1998GTP]

Originally posted by Fish@May 16 2005, 03:28 AM
You sure you have a 180 thermo?? Mine barely gets over the second line sitting in traffic.

[snapback]83958[/snapback]​

YEAH, THE PIZZAGTP INSTALLED IT FOR ME!!

 

[xierxior]

your guage is off or that's a 195 tstat

 

[SaturdaysGS]

He has a stock pcm so stock pcm fan turn on times.. Looks about right to me when your standing still.

 

[xierxior]

oops missed the stock pcm part he should have a pcm with 180 degree tstat fan times anyways..

 

[SaturdaysGS]

yeah, and then maybe he would have kept up with me

Mike, it may be time for a new o2 sensor..

 

[xierxior]

*takes deep breath* heres what I had to replace to get my mileage up

delco o2 sensor
delco tps sensor (was bad and causing really bad mileage 10mpg)
delco wires
delco plugs (iridium).. shitty don't buy them they knock like mofo's
pcv valve
FWI (I have a 97 they had REALLY shitty airboxes)
cleaned throttle body out (IAC passage was a little clogged)
ran seafoam through the motor and saw tons of crap come out the exhaust I'm sure all that carbon was blocking air and possibly causing KR

there you have it 97 GTP /w 5 degrees of KR :lolsign: and 106k gets 20mpg city and anywhere between 24/30 on the highway depending on speed 70mph seems to be a sweet spot


I get about 20 if I keep my right foot off the pedal 15'ish if I romp on it

 

[SaturdaysGS]

quick off topic question, what did you do with the seafoam, run it thru a vac line? im thinking of getting the gm top end engine stuff (same as seafoam I think) aswell as having my fuel injectors cleaned at some shop, then an oil/filter change. edit also did you take off the throttle body?

 

[jk99gtp]

Originally posted by SaturdaysGS@May 17 2005, 12:41 AM
quick off topic question, what did you do with the seafoam, run it thru a vac line? im thinking of getting the gm top end engine stuff (same as seafoam I think) aswell as having my fuel injectors cleaned at some shop, then an oil/filter change. edit also did you take off the throttle body?

[snapback]84100[/snapback]​

http://www.clubgp.com/cgi-asp/mods.asp?modid=69

 

[SaturdaysGS]

Originally posted by jk99gtp@May 17 2005, 12:48 AM
http://www.clubgp.com/cgi-asp/mods.asp?modid=69

[snapback]84101[/snapback]​

sweet, just what I was looking for, thanks!

 

[jk99gtp]

Getting 12mpg must stink. Currently my headers are leaking in 3 different areas and I still am seeing over 20mpg (60% city , 40% hwy)

I heart my Powrtuner :lolsign:

Like Nick said, replace your o2 sensor first. If its worn with mileage it will definitely kill your gas mileage..

Good luck..

 

[SaturdaysGS]

Originally posted by jk99gtp@May 17 2005, 12:53 AM
Getting 12mpg must stink. Currently my headers are leaking in 3 different areas and I still am seeing over 20mpg (60% city , 40% hwy)

I heart my Powrtuner  :lolsign:

I gotta get me one of those :lolsign:

 

[jk99gtp]

Originally posted by SaturdaysGS@May 17 2005, 01:06 AM
I gotta get me one of those  :lolsign:

[snapback]84111[/snapback]​

Let me tell you, next to the intercooler its probably the best mod I've ever purchased for my car.

Frying PCM's suck tho :lolsign:

 

[xierxior]

dude you're going to look like hoolio cruising around with a big ass cloud of white smoke behind you :lolsign: I was romping on it cruising down foster and everyone at the light was like red car flying like a missle with a big cloud of white smoke behind it :lolsign: