I'm getting poor gas mileage and have tried most everything I can think of. Any suggestions?

20

Asked by May 20, 2015 at 06:44 AM about the 2002 Pontiac Grand Am SE

Question type: Maintenance & Repair

I've replaced my plugs, wires, air filter,  MAP
sensor, and PCV valve and am still getting
poor gas mileage. Any suggestions
recommend?

13 Answers

95,095

Could be your injectors, put a can of SeaFoam in the fuel tank and run it for about 20 miles using all kinds of driving, ie stop and go, highway speeds, slow take offs , fast take offs, then fill it up and start your mileage tests.

1 of 1 people found this helpful.
242,115

What is your MPG and how are you calculating it. How does the car run otherwise?

2 of 2 people found this helpful.
67,445

A common problem is the transmission not shifting into overdrive and then the torque converter clutch is supposed to lock in. If you have a tachometer, at cruising speed, the tach should be around 1500 RPMs. My '00 Grand Prix GT has lost overdrive and torque converter clutch lock in. At around 60 MPH the tach is around 3000 RPMs which kills gas mileage! HTH. -Jim

20

Can't hurt to try the seafoam, also. I'll try anything that's cheap.

20

I've just been doing a rough estimate with gallons per fill up and miles on my trip odometer. But, it seems sometimes I'm getting around 15mpg, with an average of 15 miles Highway daily. It idles rough at start up, sometimes. But, once I'm driving, it runs fine. Also, I'm going to check out the tachometer on my way to work and see what it's running at.

2 of 2 people found this helpful.
67,445

Ok, good. Pay attention to how the transmission is shifting as well. The tach will tell the tale but you should notice the shifting up through 4th gear (overdrive). Then a few seconds later the torque converter clutch should lock in. You should notice a sharp drop on the tach when that happens. HTH. -Jim

242,115

Rough idle can be from a vacuum leak to a misfire. Try cleaning the throtlte body. Is the Check Engine light on?

20

No check engine light currently. But, on the freeway today, it was running around 3000rpm at 60mph then dropped to between 2000 and 2300 at 70mph.

95,095

It did finally shift into high, but it looks like the lockup never occurred hard to say at this point, but you could be looking at a transmission problem, have the system scanned, it should show if it is a tranny problem, solenoids or control processor.

67,445

I agree. My '08 Grand Marquis runs at about 1200 RPMs at 60-70 MPH. Your numbers seem high. Looks like a tranny problem. HTH. -Jim

These are only 4 gear trannys that why they run so high.

At 55 mph my tach runs a smooth 1500 and im getting great gas milage! But also i don t have a heavy foot either!

I have a 2004 GA and it shifts so smooth you have to watch the tach and it will tell you when you go through your gears and when it shifts into overdrive you ll see your rpm on your tach drop around 1500 rpms at 55 or 60 mph! Im getting around 21 mpg! I guess i just lucked out when i bought it last week

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