Help!! Very bad MPG 15-17 MPG!!

[solkjare]

My MPG is really bad. I got average around 15-17 MGP!!!! I got my P5 auto tranny 3 months ago. It had 64900 Miles on it. It has been running very good. No CEL. I put less than a thousand miles in 3 months mixing in city and highway (70:30) as i said i only got between 15-17 MPG. What i did is I changed air filter, check tire pressure, add fuel injection cleaner and reset the ECU. No luck, nothing improve. What should I do? Help Please!!!

 

[Tasty]

Spark plugs would be MY next thing to replace if I were you. Just go for OEM style NGK plugs, there is NO POINT to expensive "performance" type plugs. That is horrifying mileage though. Check the plugs. Where did you buy the car? Individual? Dealer?

 

[solkjare]

Thanks for quick reply!! I bought it from the dealer in chicago, It is an 2002 model. It came with 3000 miles warranty, everything works fine, the car run very smooth except horrible MPG. I will replace spark plugs asap. Anything else? I should do?

 

[16902]

You do know that after you reset the ECU that the car will run rich for a period before it has recalibrated, right? That will cause horrible mileage.

 

[solkjare]

Do you know how long for the running rich period?

 

[16902]

Do you know how long for the running rich period?

It will kinda depend on how much driving you have done since you reset it. If you drive a lot, it may only take a few days. If a lesser amount, probably about a week or so.

 

[smo0f]

up to 200 miles on avg

 

[solkjare]

Thanks , I have put ~ 220 miles after I reset the ECU. I am waiting for the next tank. Hopefully, I will get better, MPG

 

[16902]

Yeah, if you are still doing that bad, then I don't know what it could be.

 

[smo0f]

if you still have warranty, take it back to them. you're supposed to be running around 32 city, 24 hwy. 15-17 is unacceptable. could be spark plugs, o2 sensors, catalytic converter, or vacuum leak(s). just take it to them and tell them you don't want it back until it's fixed

 

[solkjare]

My warranty will be expired on the end of this month. It will take about 2 hrs driving to the dealer. So that's my problem. I am trying to do from minor thing that i can do myself. If there was problems with O2 sensors or catalytic converter, the CEL should be on right? I don't get any code.

 

[smo0f]

no idea man.

 

[solkjare]

thanks anyway.

 

[16902]

you can try spark plugs and wires but i don't see why that would cause such mileage. try cleaning the EGR valve......maybe. still, it sounds to me like the ecu still needs to finish recalibrating. i know everytime i did that, i would get under 200 miles on a tank. ouch!!

 

[solkjare]

yeah I got just above 200 miles on a tanks. and I think I am gonna be broke if the mileage still be this awful. I will post again when I change the plugs

 

[pasadena_commut]

yeah I got just above 200 miles on a tanks. and I think I am gonna be broke if the mileage still be this awful. I will post again when I change the plugs

That's really cruddy mileage. Either the motor isn't working very well or it is and the power is being frittered away somewhere else as drag.

Other things to check:

1. Cylinder compression
2. All motor related sensors (MAF in particular)
3. (Partial) Blockage in exhaust
4. (Partial) Blockage in intake
5. Dragging brake
6. Transmission fluids
7. Alignment (as in, one wheel way, way, way crooked)

I agree with an earlier poster though - take it back. You could screw around with this a long time, at this point it's the dealer's problem. If it is an inexpensive fix, he'll do it. If it isn't, do you really want the car?

 

[Crazy D]

I have this problem.. .no cel; but I found that my first cat is shot and is killing everything

 

[pasadena_commut]

I have this problem.. .no cel; but I found that my first cat is shot and is killing everything

In what way is your first cat "shot"? I've had bad catalytic converters before (not on this car thankfully) and the only symptom is that it fails the smog test. Is yours clogged or something?

 

[solkjare]

I have this problem.. .no cel; but I found that my first cat is shot and is killing everything

What did you do then? How can I know if my cat is also shot? How bad your MPG?

 

[solkjare]

That's really cruddy mileage. Either the motor isn't working very well or it is and the power is being frittered away somewhere else as drag.

Other things to check:

1. Cylinder compression
2. All motor related sensors (MAF in particular)
3. (Partial) Blockage in exhaust
4. (Partial) Blockage in intake
5. Dragging brake
6. Transmission fluids
7. Alignment (as in, one wheel way, way, way crooked)

I agree with an earlier poster though - take it back. You could screw around with this a long time, at this point it's the dealer's problem. If it is an inexpensive fix, he'll do it. If it isn't, do you really want the car?

Thanks for your suggestion. I love this car and I wanna keep it. I 'll let my mechanic check it first because he is closed to my house. If it is an expensive fix, I will have to drive 2 hours to the dealer then.