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Absolutely awful gas mileage 98 GTP

Q

Quickbird144

New member
Picked up my GTP a few days ago. Has 170k miles on it. Overall runs great. No CEL, doesn't run weird, etc. The car had sat at a dealership since August 2015 before I got it and Carfax showed registration stopped late 2014. I'm thinking it has been out of commission for some time. I've put some photos of my MPG, the range, and where the fuel gauge sits. It's terrible. I'm sure it is in need of a decent tuneup, can anyone point me in the right direction to bring this up? Any help would be greatly appreciated.



 


How far do you drive a day?

If that's 1/4 tank and under 80 miles or something, then yeah you might be really wanting that tune up.

Clean the throttle body and MAF sensor and new spark plugs for starters, then see where you are at.
 
#1 the DIC is inaccurate. I wouldn't trust it to save my life.
#2 fuel mileage can change drastically with lots of idling. If you drive a lot in the city, your mileage will suck. If you drive a lot of hills, your mileage will suck.

Lastly, make sure you are running premium.
 
looks just like mine lol all local driving nets me 14 to 16 if i light foot it. it dips to 10's if im beating on it local.
 
Tune up. Not a cheap tune up. Air filter. Plugs. Wires. Oxygen sensors. Oil change.

If all else fails. Winter gas
 
I don't drive with a heavy foot at all. I just got out Friday and do a mix of city and highway. I barely ever hit the boost. Everything is bone stock. Should I add a fuel filter to that list as well? Would replacing the MAF do me any good? Not getting a check engine light on it.
 


Don't change the MAF, just buy MAF cleaner and give it a good cleaning. Fuel filter would probably help a good amount too. I changed mine and mine had 125000 miles and it made a huge difference.
 
the most drastic fueling affecting tuneup item is the upstream O2 sensor., its the primary device used to determine a/f ratio, they skew as they get older and no longer switch at stoichiometric. if your sensor has over 50k on it, then yes its likely that its skewed and not reading properly.

the O2 sensor is one of the "trusted" sensors, which means the pcm assumes its perfect, even when it isnt, the vehicle would have to be equipped with a wideband or another NB sensor for the pcm to have any diagnostic functions for the upstream O2....so they just assume its perfect

dont buy bosch, get denso/NGK/delphi/ac delco
 
You may just need to reset that. My GTP stays at 21.5 in moderate traffic and actually gets about 20.4 and I floor it once or twice each hour of usage. If you're not having an obvious poor running problem reset the DIC in that mode (hold button until it resets) before you go throwing parts at it. The DIC is giving you a long-winded average that may not include much driving but might include lots of time static, idling.
 
idrivejunk said:
You may just need to reset that. My GTP stays at 21.5 in moderate traffic and actually gets about 20.4 and I floor it once or twice each hour of usage. If you're not having an obvious poor running problem reset the DIC in that mode (hold button until it resets) before you go throwing parts at it. The DIC is giving you a long-winded average that may not include much driving but might include lots of time static, idling.
Click to expand...

I will get that mileage with straight driving, but as soon as I come to a stop, it starts drastically dropping.
 
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