You should also consider the fact that there may be more than one problem.
Most of the possibilities have been covered in previous emails but dont fall
into the trap of thinking that just because you fixed one thing and the
problem did not go away that it was not contributing to your poor gas
mileage. Most the things that have been mentioned - just as replacing
spark plugs, O2 sensor, etc could be contributing. Since they are relatively
low cost items if you have been doing a lot of towing with the truck it might
be a good time to replace them anyway. You should also look at things such
as how the wheel bearings are adjusted (if they are loose if might contribute),
transmission, water pump (bearings seizing?) , brakes dragging, etc. Also
has the load you have been towing changed recently?. I used to work in a
dealer and one of the traps the mechanics would fall into was thinking just
because they replaced on bad part that they had gotten the problem. These
were the types of cases where the car would come back two weeks later
with a really irate customer because he thought the problem had been
taken care of. You should bear this in mind when trying to track down this
problem, if you have replaced the spark plugs and the problem still exists
dont replace them again - move onto something else. It might cost you more
money but at 3-4 miles to the gallon the cost of most of the parts is not
going to add up too badly if you compare it to the gas you are wasting.
Especially not at the prices now.
Good luck
At 01:28 PM 5/18/2001, Alan Pozner wrote:
>Dragging brakes ?
>
>
>----- Original Message -----
>From: "James A. Crider" <autojim@worldnet.att.net>
>To: <autox@autox.team.net>
>Sent: Thursday, May 17, 2001 9:20 PM
>Subject: Re: Tow Truck Question
>
>
> > My friend Pat Washburn asked:
> >
> > >Subject: 1998 Chev 3500 Dually w/ 454 engine..
> > >
> > >Problem: Absolute sucky fuel use. I don't mean "well you gotta big
> > >engine, of course it's going to suck" kind of mileage. I mean like 3 to
>4
> > >miles per gallon. Empty. Not towing.
> > >
> > >Tried: Dealer and independent repair shop evaluation. (One shop even
>had
> > >a brand new, supposedly very high tech Snap-On digital engine anylizer.
>No
> > >information from them other than "Well, the compression is good.")
>Result
> > >is that all OBDII readings are within spec. Engine has around 49,000
> > >highway miles. We put on a new fuel regulator, no help. (Thought there
>was
> > >a TSB.)
> >
> > Check the O2 sensors -- I gotta think something is latched lean, which
> > causes the ECU to run the engine way rich. Running that rich will lead to
> > really high EGTs, too, which will kill the cats, too (by melting the
>insides).
> >
> > >It runs great. No one can seem to figure out why this is. Can anyone
> > >relate any common experiences?? Any suggested areas to look at? Thanks
> > >gang!
> >
> > Are the plugs okay? Something like this, the plugs should be nearly
> > dripping wet with fuel fouling. Vapor cannister purge system is another
> > possibility. But nearly all of these should twig something in OBD-II. Is
> > the crankcase full of gas? Air filter clogged? Exhaust plugged?
> >
> > Check for fuel leaks, stuck injectors, the neighbor kid with the 2nd-gen
> > Camaro (you know the one: mullet haircut, the car has air shocks and
> > extended spring shackles, and the rear tires stick out of the wheelwells
> > about 3") that, despite $2/gallon premium in the area, has enough cash for
> > a new set of chrome exhaust tips for his 2" pipes, the driver who seems to
> > like running 4WD Low Range all the time or mats the gas pedal and
>regulates
> > his speed with the brakes, a driving regime that consists entirely of
> > highway speeds uphill and into the wind, and that same neighbor kid saving
> > gas by hooking his Camaro to the back bumper on the morning commute...
> >
> > Jim Crider
> > autojim@att.net
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