Fuel Mileage?

[eightshot627]

[SIZE=medium]2002 TB, 4.2L, 3.73, 4x4, 170K[/SIZE]

[SIZE=medium]Over the last year my fuel mileage has gone down from 19.5 mpg to 16 mpg. I have replaced the plugs AC/Delco Iridium, changed the O2 sensor also AC/Delco, thermostat and the fan clutch. New factory size tires and fresh alignment and my mileage is still at 16 mpg. No check engine light only the occasional service airbag display. [/SIZE]

[SIZE=medium]What to check next to help with mileage?[/SIZE]

[SIZE=medium]Thanks,[/SIZE]
[SIZE=medium]Walt[/SIZE]

 

[HARDTRAILZ]

Same driving conditions and habits? Same routes?

 

[eightshot627]

All the same.

 

[Playsinsnow]

Winter gas is at the pump now here. I take a slight hit in winter mpg's because of it. You didn't mention tire psi. Cold mornings will lower psi and mileage. What are they set at COLD?

Clean the throttle body/plate too. There is a how-to here.

 

[eightshot627]

37 psi cold. This is the same psi i have alway run them. I've been watching the mileage go down over a few months. Two different sets of tires. I bought the O2 senor in January finally gave up and paid someone to get the O2 sensor out in June. I cleaned the throttle body at 150k. I'll do it again over the weekend.

Thanks,
Walt

 

[808_LS_EXT]

I'm still getting 10mpg after replacing more parts than you did....
(and I got a more-efficient 2wd)
I'd be BRAGGING if I were getting 16!!

Subscribed to this thread... waiting for the "cure".

 

[Royalwapiti]

You joined the club!

I pulled a trailer with ATV over 3000 miles and hit an average of 12 mpg. I get home and while still using premium fuel 91 octane I am getting 13mpg for city and highway driving.

Same recent maintenance; plugs, coil paks, O2 sensor, PCM Tune.

There's something about these 4.2L that gets garbled and destroys the fuel mileage.

 

[D3vious]

21 mpg for me, must be I got one of the "good" ones

 

[HARDTRAILZ]

I average between 15 and 16 w 35s and lots of extra unaerodynamic weight.

 

[eightshot627]

Wow 12mpg that would only inspired me to sell to or give it away. I bought it because my friend's 06 gets 22mpg. The best I saw was 19.5. My wife's Tahoe gets 18 and has way more power and comfort.

The tire pressure was at 32psi so I bumped it up to 37 psi and cleaned the throttle plate. After a couple of fill ups I will report back.

Thanks,
Walt

 

[Harpo]

There's something about these 4.2L that gets garbled and destroys the fuel mileage.

That's true.

There must be something that's get f...ed up somehow. There is no logical explanation to why some get 21_22 mpg and others only 10-12 mpg, in the same kind of truck.
Me for instance, I got 19 mpg combined when I bought my truck. That lasted for two years until my thermostat was stuck partly open.
I changed that and all would be well again I thought. Fat chance, I never seen that mileage again after that.

Instead I got about 17 mpg and dropping ever since, I'm now down to 14.6 mpg combined. That's no fun with gasprices around $7/ gal.

I do my best to figure out what's happened, I'm changing out sensor and parts from my spare engine one by one to see if there is anything that makes any substantial difference in mpg, but nothing yet.
Hope I find anything good soon because I don't know how long I can afford this mileage.


You may think it's better to change engines but that's my last option . As this is the family's only vehicle it would have to be done in one evening/ night at my friend's shop, it's doable but not something I lookin forward to so it would be my
absolutely last option. It would probably be very nice since it is a Saab 2005 engine with only 5800 km on it not even broken in or dirty.

 

[Mounce]

That's true.

There must be something that's get f...ed up somehow. There is no logical explanation to why some get 21_22 mpg and others only 10-12 mpg, in the same kind of truck.
Me for instance, I got 19 mpg combined when I bought my truck. That lasted for two years until my thermostat was stuck partly open.
I changed that and all would be well again I thought. Fat chance, I never seen that mileage again after that.

Instead I got about 17 mpg and dropping ever since, I'm now down to 14.6 mpg combined. That's no fun with gasprices around $7/ gal.

I do my best to figure out what's happened, I'm changing out sensor and parts from my spare engine one by one to see if there is anything that makes any substantial difference in mpg, but nothing yet.
Hope I find anything good soon because I don't know how long I can afford this mileage.

Partially clogged cat from the bad thermostat maybe? How long was the thermostat bad before you changed it?

Edit- btw, $7/gal is crazy! It's dipping below $3 in my area.

 

[Harpo]

I think I drove around for two weekends before I got a chance to change it.
But that's 3 years ago now, and my most reason problem is that the cat is most probably falling apart inside so I don't think that was it. It was not any other signs for a clogged cat at that time.
$7/ gal IS crazy, we talking Europe/ Sweden here, this summer it was $7.90/ gal and I was doing 12mpg with my caravan behind :-((

 

[Mounce]

Dang man, it's expensive to drive over there!

 

[808_LS_EXT]

this summer it was $7.90/ gal

reading that tore a hole in my back pocket....

 

[Harpo]

Yeah
I just cope with it because I only use it for weekends, if I had to take it to work I would be bankrupted.
I have five kids and I refuse to drive a wv bus or some other boring car. I had a Chrysler T&C before this and that darned thing just fell apart all the time.
There is not alot of nice sevenseaters to choose from unfortunately.
I love my TB Ext.

 

[Denali n DOO]

I've seen 24.3 mpg on the dic on a 1 hour drive to my trailer. And that's a 5.3L

lol, my buddy just pulled a travel trailer to Newfoundland in his ford f150 5.4L and his average was 6.03 mpg....ha ha ha ha ha, I still can't stop laughing at that number

 

[Mounce]

that's horrible mileage!

 

[808_LS_EXT]

lol, my buddy just pulled a travel trailer to Newfoundland in his ford f150 5.4L and his average was 6.03 mpg....ha ha ha ha ha, I still can't stop laughing at that number

Ouch, how far to Newfoundland?
Mighta been cheaper to fly there and buy a travel trailer...

 

[DAlastDON]

Do your precats in at the end of the exhaust manifold sound like they have something rattling inside them? If it has gotten that far then back pressure could suck the particles into the engine.