97 sl2 drop in mpg

my 97 sl2 has ran great and I just hit the 160k miles. I use to get

27mpg in the city and 35 to 37mpg on the hiway but recently something has changed. My mpg is now about 24-25mpg on the hiway and 20 in the city. Pu new plugs in as normal (twice a year) but that didn't seem to mke a difference. Over the last 2 years the car has had new plugs, new cts, new air filter, changed oil every 3months, new tires and struts all around, upper motor mount and the sensor that is up front by the air intake. ( it is actually the same one as the cts ). and finally the forward o2 sensor. So where should I start looking to find out why the drop in mpg's. I did notice that when I changed wires that 3 terminals were very corroded on the same coil ( or whatever they are called) which a cleaned and buffed off then put conductive grease on them but noticed that they had corroded up again after about a year. The other set is nice and clean and always has been so. Is that a coil problem with that pair or just something that happens. I really guessing at this time so please point me in the right direction. Phil
Reply to
p_vouers
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sorry I meant 2 terminals ( actually 1 and 2 on the coil)

Reply to
p_vouers

YOu did not say where you live but MPG can drop a good bit in winter in some areas due to temps and alchol in fule whigh lowers BTU content and there for MPG. You might check the ECS because if it is bad and keeping engine rich, MPG will suffer.

----------------- TheSnoMan.com

Reply to
SnoMan

Thanks snowman.. yes I live in wisconsin but other years it didn't drop that much and this has been a very warm winter. Is the ecs the same as thecoolant temperature sensor.. oh I also might say that I had the engine thermostat replaced (saturn) but that seemed to make it worse but the engine does warm up faster now and maintains a better temp in the winter.

Reply to
p_vouers

Yes it is the same and if it has never been replaced (ECS) you should consider it because if it is bad and telling PCM that engine is cooler than it is, it will run mixture richer. ALso on the alchol thing. Not sure if it applies to WI but oil companies stopped using MTBE in fuel about a year ago and replaced it with alchol which lowers BTU content of fuel.

----------------- TheSnoMan.com

Reply to
SnoMan

The very first thing should be to read the stored codes. They may tell you the answer without having to replace any parts that aren't to blame. Autozone and other parts stores do it for no charge.

Lane [ lane (at) evilplastic.com ]

Reply to
Lane

it has never thrown a code and my codereader never showed anything.

first thing should be to read the stored codes. They may tell you

messagenews: snipped-for-privacy@j27g2000cwj.googlegroups.com...

Reply to
p_vouers

Havent followed the thread but a real scantool would be a good thing to hook up to pull some actual sensor values. Some things like a ECT sensor could be out of range and the ECM probably wouldnt know it...

Reply to
BläBlä

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