My car is only getting 11 to 14 mpg. I have already replaced coilds, spark plugs, air filter, fuel filter and the it didn't seem to improve at all. Any suggestions?

325

Asked by Feb 08, 2016 at 12:37 PM about the 2001 Pontiac Grand Prix GT

Question type: Maintenance & Repair

19 Answers

330

How many miles on the vehicle? Use a gage and check proper fuel pressure. Also, see if fuel pressure will hold for a bit with everything off. Can you check for applicable trouble codes, if there are any? Some of the national brand auto stores will check codes for free, if there are any.

Best Answer
325

The car has 190,000 and not long ago the car was getting 26mpg. Then it started to decrease more and more. Then the alternator went out and caused a load of problems. It cause the car to hesitate when shifting from 1st to 2nd and now I think the 2nd hear is starting to go. I know my fuel is still origianl but the car doesnt have any lack of power or anything

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60,565

The oxygen sensor or the mass air sensor may be bad. If the engine is getting the wrong fuel/air mixture then fuel economy suffers. When was the last time you did a tuneup and filter change?

325

As far as I know the car hasn't ever had a tune up. A air filter or a fuel change? Is there a way to see if the fuel is getting into the oil or something?

330

Do you have super charger or turbo on this? Those engines don't usually last long. You can smell of your crankcase oil dipstick, if it smells like gas, either the oil and filter hasn't been changed in a long time or you got fuel getting into the crankcase. I agree with Full, a tune-up might do wonders? I don't think I've ever seen a vehicle with that many miles that got 26 miles to the gallon, but, I haven't seen everything.

325

It's completely stock but when I changed the plugs I notice that cylinder s 3,4,5, the plugs had alot of white powder like stuff in them. I don't know if thats normal or not but last time I changed my oil the oil had a strong gas smell to it

330

It may depend on how long you go between oil changes? Your fuel pressure regulator could be leaking, or a fuel injector. Sometimes a coolant temp sensor may cause it to burn more gas?

325

I go every 5,000 miles between oil changes

330

I usually go with whatever the manufacturer recommends. I try to change mine about every three months. I'm retired, I won't put many miles on mine in three months, probably less then 3000 miles. Like FOR said, 02 sensors are part of a tune-up. A fuel pressure gage should tell you if there is a fuel pressure leak.

325

Could the catalytic converter be plug? It's still the oringal one.

330

Usually if exhaust is clogged it will cause vehicle to bog down.

325

It this helps any sometimes when it gets cold and the car shits for a while it starts for a second or 2 and then dies then starts up just fine. Sometimes it starts up and bogs down to 400rpms then picks up

60,565

Change the air, oil and fuel filters.

325

The air filter is a brand new k&n filter

60,565

Gas in the oil indicates a leaking fuel injector which would explain the drop in MPG. I would check that out and change the gas contaminated oil before you damage the engine. K&N filters are great but be sure and oil it.

60,565

If the cat is plugged the engine power would not be good.

325

Whats the easiest way to test the injector's?

325

How much does a tune up usually cost for these cars?

325

I found out the reason for the bad gas milage being so bad. And usually put marathon in it but last time I put shell in it the car got 17mpg. I usually go with mrathon cause usually its cheaper but now I'm just gonna stick with shell gas.

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