Dropping MPG

Are you using the same flavor of gas? Might the fuel blend have changed?

If you were using real gas and switched to some kind of alcohol blend that's going to drop your mileage.

Jeff DeWitt

snipped-for-privacy@ns.sympatico.ca wrote:

With the 4 liter in a WJ you should be averaging overall between 18 and 20 mpg if you are a conservative driver.

Are you figuring your mileage with a pencil and paper or the EVIC?

I believe that the gas blend is changed in the winter for cold climates. I guess it could be possible that the winter blends are arriving already. Might be worth an ask at the gas station, but they may not know unless you talk to someone at a higher level than cashier.

Chris

Other comments on measuring techniques and alky gas are good for some of the change but if it seems to be outside temp sensitive, I'd check the thermostat and engine temp. If the thermostat does not allow engine temp to get over the computer minimum (around 140 degress depending on the sensor and engine/year), the computer keeps it in open loop (and very rich) mode. You temp guage should be reading around 200F or 210F within

3 to 5 minutes of a cold start and low sppeds at say 40F outside.

I've had similar issues with other vehicles at this time of year or whenever the morn> Hi all, after purchasing the '04 GC I posted about a few weeks back, I

O2 sensor can do this, but it's more likely in warmer weahter. Does your area switch to "winter blends"?

FWIW, this is what I use to track milage and other stuff.

instructions not included. :)

I get that kind of mileage drop when I have to use an alcohol mix in the gas.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Not a real detailed log, unless I'm driving on buisness. I use excel to keep track of milage and maintenance.

Thanks for the input folks, here is some more info. Yes my area does switch to a 'winter' blend but not for another month or so. No I do not use an alcohol blend of fuel ( E85 is just WRONG!! ). The brand and grade of fuel are the same. I calculate my MPG manually and compare that figure with the on-board smarts, the difference is less than 0.1 MPG so that doesn't account for an 8 MPG drop .

The engine temp when hot is 140 C or about 195 F, I wouldn't think that this is too cold but I could be wrong. It is at temp after 4 or 5 minutes.

The only other thing I did was to change the plugs, the NGKs I took out appeared to be running OKish ( #6 seemed a bit rich) but the gap was over .060 ! . I have checked all electrical plugs and connectors just in case I accidentally disconnected something but all were OK.

Kevin

What kind of plugs did you put back in? Some Jeep engines won't run on bosch plugs....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

I've had tires lose pressure with sudden temp changes. That usually shows up as a gas hog, especially if I'm loaded up in the rear. A vacuum leak can also make a big difference.

OK, engine vacuum is 16 in/hg at idle in gear, I checked the brakes for sticking calipers, all OK there, I tend to run my tires at 40 psi year-round. I did however use Bosch Plus 4 plugs when I replaced the NGKs. I have used Bosch plugs in Honda, Ford BB and SB engines, Chev L6, Toyota L4, VW L4, Audi V8 and BB Dodge engines with no problems.

I would find it strange that the Bosch would not work in my 4.0L but stranger things have been known to happen.

Any recomendations on plugs for a 4.0L ? Or plugs to avoid ?

Kevin

I use Champion plugs in both my Jeeps and get about 23 mpg in the CJ7 on the highway loaded or empty and over 24 in the Cherokee, when loaded for camping, on the highway.

If the NGK were working well, I would go with them also.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Kevin,

I run with the regular Bosch Platinum plugs (#4203) in my 4 liter and put the regular 4230s in Mark's 4.7 liter and they run flawlessly.

Some people prefer copper plugs, in that case I use the Bosch Super # 7562s

I started with the Bosch Supers about 30 years ago and the regular Platinums about 20 years ago and I've never had any reason to change back to Champions (or any other brand) Everyone has their personal preference though.

I've considered getting the +4s next time, are you saying the mileage dropped just after changing plugs?

Bosch guarantees the plugs to run superior to other brands and will refund your money

You might possibly have leaking or sticky injectors It wouldn't hurt to clean the fuel system and injectors. Pat Goss on Motor Week recommends adding a can of cleaner to a full tank of gasoline and running that tank as low as you dare, refilling with just gasoline and running that tank as low as you dare, then adding the cleaner to a second tank and running that tank as low as you dare. Brands I have used and recommend include SeaFoam, BG44k, Berryman B12 Chemtool, and Techron Cleaner (not the Cleaner with Techron)

Throttle Body Cleaning: All this requires is a can of sensor safe spray cleaner and an old toothbrush.

What vacuum reading do you get in Neutral or Park? Your 16 inches is just a tad low, recheck the idle in park and also check for a vacuum leak.

I found out early on that once the pump stops my MJ will hold just short of 4 more gallons if I trickle it in until the filler hose is full - but only if it's on a level surface. I keep my mileage figures using a boxcar average of the last 4 tanks which gives me a much better trend indicator..