only 14mpg, why?

[midohiomoparsource]

1993 Lebaron GTC convertible 3.0 auto.
Wifes car, and she can only get about 150 miles on a tank of gas!!
Car has new plugs, wires, cap, rotor, air filter, all stock units.
It doesn't have ANY codes, I already checked that.
Shows no signs of raw fuel coming out exhaust, and plugs just looked old when I replaced them.
Overdrive is working, you can hear/feel it shift, and see it on the tach.
This is her daily driver, and with gas almost $2.50 or so a gallon, we need to get it right.
Any thoughts?

Matt

[shadow88]

Could be a lazy 02 sensor, exhaust leak pinning the fuel trim rich, incorrect ignition timing, stuck open thermostat causing it to never reach closed loop, only driven on short drives, there's a number of things to check.

[turbovanman²]

^^^what he said. Is the tailpipe soot black?

I would say that due to the worn plugs and the usual 3.0L oil burning, :eyebrows: the ox sensor has probably taken a dump. I would disconnect the battery, replace it with an NTK or OE unit and see what happens. Also as stated, make sure the engine is reaching 195 deg.

[midohiomoparsource]

The plugs were just old. They showed normal wear.
The strange thing about the exhaust, it has the dual tips off the muffler, but the normal cold moisture burning it only comes out one of the two tips, thought that was wierd. Anyhow, nothing unusual coming out the exhaust that I can tell.
Car does not get driven hard, it is my wifes and she is normally easy on cars.
Uses NO oil either.
We just put new tune up. It still has a very slight miss, thought maybe fuel filter, so I got one to put in it, figure it can't hurt lol.

I will check codes again and see what happens.

Matt

[midohiomoparsource]

Just went out and checked and I do get codes 12 and 17.
I know 12 is the battery thing, so not worried about that, but what is 17? I am going to do some searching to see if I can find it next.

Also, on the tailpipe, there is black soot on the one tip, but nothing on the other. Thought that was strange, so I started it and covered the one with soot with my hand, and nothing came out the other tip. Is it just decorative or could it be plugged? Also, sometimes after car has sat for awhile, like overnight, you can smell gas fumes. Car has NO leaks that I can find, but it smells like pure gas. Coming from the rear of the car, near tires.

Matt

[3nglenn]

Code 17 is engine staying cold too long... Check out http://minimopar.knizefamily.net/fault/code17.html

[midohiomoparsource]

Yeah, it says temp sensor is bad.
Is this 3.0 specific or will one out of a 2.2/2.5 work?

Matt

[3nglenn]

I suppose you could try it (swapping coolent sensors, I think they're interchangable) as long as the plugs are the same. I don't know too much about 3.0's. How about getting a new 195* thermostat? Whats the temperature gauge in the car read after running 10-15 minutes. Keep us posted. :nod: G.P.

[looneytuner]

Fuel smell. Gas line at tank or filter. The less you drive the worse the mileage. It seems like every car in Detroit has a new gas tank also. Where did it come from??

[Whorse]

Simon changed the cat and O2 on my VNT and I gained about 10mpg, so I'd seriously check it if I were you.

[turbovanman²]

Car staying cold to long is a thermostat. A bad coolant sensor will set different codes. I would change the ox sensor and thermostat, clear memory and drive, :nod:

Yes, 2.2/2.5 coolant sensor is the same.

[Turbodave]

Also, on the tailpipe, there is black soot on the one tip, but nothing on the other. Thought that was strange, so I started it and covered the one with soot with my hand, and nothing came out the other tip. Is it just decorative or could it be plugged?

On the 3.0l cars the dual tip mufflers have one tip that's just there for show.

[midohiomoparsource]

Thats what I thought, I guess I could have just looked lol.
Thanks,
Matt

[midohiomoparsource]

Ok, I got to drive the car tonight for about 11 miles, and the temp guage never moved off C. So, I will be putting a new temp sensor in this week.
Also, even after the tune up, the car still runs a little rough sometimes.

Matt

[eyeball]

Ok, I got to drive the car tonight for about 11 miles, and the temp guage never moved off C. So, I will be putting a new temp sensor in this week.
Also, even after the tune up, the car still runs a little rough sometimes.

Matt

As if turbovanman's explanation wasn't enough, you have just verified that it is indeed the thermostat causing your problems. Code 17 tells you that the ECM is seeing the coolant temp too low for too long and you have just witnessed the temp gauge is not reaching operating temp. The ECM reads coolant temp from the ECT and the gauge reads temp from a single wire sender. They are separate sensors/senders. Please do as
turbovanman, 3nglenn, and shadow88 have all suggested and replace your thermostat.

[jckrieger]

It never hurts to check the fuel pressure regulator, I've seen them stick and cause the fuel pump to max out (around 98psi) or the diaphragm will rupture and leak gas throughout the fuel lines. I'm not sure having a stuck thermostat will make you lose 10mpg, as I've driven with a broken thermostat for months and noticed only a slight decrease in mileage.

[midohiomoparsource]

I can see the coolant temp sensor being a problem. If car is running cold, or so it is reading, it will use more fuel, like a choke system on a carb. car.
I will be looking into it Monday.

Fuel smell is coming from passenger side, and it isnt all the time. I have a new filter for it that will get put on Monday as well.

The t-stat I may change, the car has great heat, so not sure on that one yet. I can change it anyhow, doesn't cost much lol.

Thanks all who have replied and helped.

Matt

[Domino]

It never hurts to check the fuel pressure regulator, I've seen them stick and cause the fuel pump to max out (around 98psi) or the diaphragm will rupture and leak gas throughout the fuel lines.

i just found out that the vacuum line to my FPR wasn't even hooked up...hope connecting it helps my mpg go up from a 11.3 average.