<DIV id=post_message_37125 q6X3S="0" C16nS="6">My 92 LeSabre was consistently getting over 30mpg on highway, even as much as 34 one time. Speeds between 60 and 70 mph. Three weeks ago, took 550 mile trip and when we got to destination noticed that engine was running very rough, missing, etc. Went to mechanic shop, replaced coil pack, and all was well. On return trip, gas mileage was down to 26mpg, but I was driving 70 to 80 mph so I chalked it off to leadfoot.

Yesterday it registered 20mpg, most of it on highway. Any ideas what could be going on here?Engine light was not lit and engine runs smooth and feels strong.

There is one thing wrong: cruise control cuts out or acts goofy sometimes. Could there be a vacuum problem that causes both these problems?</DIV><! / message ><! edit note >

more than likley when the coil pack went it eather fouled a plug...
or burnt up a plug wire.

replace both. when you replace anything inside of the ignition system.

;)

plugs and wires need to be replaced.

Thanks, TrippleT. The mechanic who changed the coils said two of the wires weren''t getting all the juice they should and that I should replace the wires. That would explain it. I''ll also doplugs as you suggest. Will report backwhen job is done.

I have owned this car for a year and never replaced plugs or wires. Examination of plugs revealed worn electrodes and very large gap. A couple werewhite on ceramic, all the rest were dark. There was no tan anywhere. Wires were cheap replacements. I replaced all with new AC plugs, gapped to .060and Belden premium wires.


Don''t have any idea yet on gas mileage but will report back when known.

sweet man, sounds like that might have been your culprit.
hope it helped.

if not i would look into your 02 censers, not always do they set off the check motor light.

but usually they do..

they should be replaced every 8000 miles. (in my opinion)
just because of the normal extreme heat and weather they have
to go threw.


there cheep and if you have the tool. they take like 3 min to replace..

this would also make your car run rich.
(why your plug was white)

Not sure i want the car to run rich. Just want it to run right. As I was changing the rear plugs I got a good look at the o2 sensor and it actually look pretty good on the outside. I do have the tool and will wait until I can check the gas mileage again before I mess with the sensor. Will get back atcha in a few days, as it doesn''t take long to go thru a tank of gas in my family. Thanks for all your help. Mike

another thing to concider would be dirty fuel system, a GOOD fuel system cleaner could also help.

good idea. I use Lucas fuel treatment a lot. if the mileage is not as good as before i''ll get some of that in the gas.

sounds good man. look forward to hearing the results.

i seriously think it was your plugs and wires

it sure was the plugs and wires. drove from our home to Nashville today and back and averaged 30mpg. that''s back to normal for this car. i installedone of those Tornado things in the air intake a couple months agoand it added at least 2mpg. one time i got 34 on a short trip. longer trips average 30mpg consistently. thanks for all your help. mike