Well, wouldn't have thought it necessary with one of these new fangled high
tech engines, but. . . Time to read the plugs.
On a deserted highway, after the engine is warmed, while cruising at your
normal speeds, reach down and turn the ignition key off. Do not lift your
foot first. Also, would be sure not to turn the key to the "lock"
position, or remove the key, as this would complicate getting to the side
of the road safely. (grin) If you are unclear why I inserted the (grin),
do NOT perform this test. . . No, I joke too much. On a modern car this
test can kill you, if you lock the steering wheel and lose brake power.
So, not risk free. . .
We do the test this way because when you are driving into the driveway, you
are accelerating and decelerating, and the fuel mix is changing, and the
plugs are therefore changing, and thus any other method would tarnish the
results.
Then unscrew one of your spark plugs. Typically, I recommend only removing
plugs from a cold head, but sometimes you can't be picky.
It should be a nice, light brown (down by the sparky part). White
(unlikely) and you are running too lean. Black (more likely), and your
engine is running too rich.
I would personally only check one plug. They'll be hot (bring gloves), and
cars will be whizzing by, and the first cop that passes will not like you
working on your truck by the side of the road, and one cylinder will not
3mpg make.
Now, this method isn't near as good as sticking an emissions sniffer up the
tail pipe. But it will tell you TODAY, FOR FREE if your truck is running
rich. If rich, you may be dumping too much fuel into the cylinder, or
maybe too much backpressure. Though backpressure seems would be more a
performance problem than a fuel problem. If nut brown, your engine is
running nicely, and this is either "normal" (ha!) or you're losing fuel
elsewhere.
Chris Eckles
White M Roadster
Pink & White 1960 Metropolitan Convertible
>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.)
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!
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