MPG drop

[jianelli]

Hey, my '00 9-5 LPT Sedan with 170K on the clock seems to be losing MPG... I have not changed the plugs for about 50K and was going to do that this week, but I was also reading that the fuel pump and or CAT Converter could also be partly responsible... I change the oil every 4-5K with full synthetic and use injector cleaner then too.... any advise? My thoughts are to do the least expensive things first....
Thanks in advance... John

[Steve440]

How about the air filter?

Steve

[Audax]

Plugs are well past the service interval so change them and make sure you use the correct spec NGK spark plugs *only* (NGK BCPR-6ESII) and replace the air filter if it hasn't been done recently. If the car hasn't been serviced properly there's no point looking for other problems before those basic items are checked.

Also, where in the world are you and what kind of journeys are you doing? It's not uncommon as we get towards winter that the mpg will drop as the car takes longer to warm up, it may well have a lazy thermostat or coolant temp sensor which will drop the mpg quite a bit, especially in winter.

[jianelli]

Thanks...
I am in Maine. I did do the air filter this summer, 3-4 months ago. The thermostat seems ok by the movement of the temperature gauge. I did recently change to an all season Cooper tire, will put on the snows in a week or two... Anything else besides the plugs to look for?
Cheers,
John

[Audax]

Even though the gauge looks good the stat can still be slow, given the price of the stats it might be something worth changing it anyway. Looks like it can get pretty cold in Maine so that might not help. The other thing to look at might be the tyre pressures. Even if they get a bit low then it seems to affect mpg quite dramatically.

If it's not those things then it could be a faulty lambda sensor but it usually makes sense to try the cheaper servicing items first. If you do try replacing a lambda sensor then it really makes sense to get the genuine Bosch item as many of the aftermarket sensors are rubbish.

[nine-fiver]

Change the thermostat.
Seriously, it is a 30min job and can change the whole car's engine management data inputs. It did to me and you don't need to put in more coolant. Just top up with water.
One of the easiest jobs on a 9-5 ever.

[jianelli]

So I put in the overdue plugs and noticed a back tire nearly flat... Sometimes I am such an idiot... I put on the snow tires (different wheels) and noticed a large puddle of oil coming out of the Left Rear shock... I ordered the parts (one for each side). Is this a difficult job? Do I need any special spring compreser? Is there any link to a procedure? I could not find one with a quick search...
Thanks,
John

[phoenix]

You will need a spring compressor to change the shock, yes. And ideally you should do both sides to keep the car stable.

Procedure is fairly simple: get the car in the air, remove the wheel

Remove bottom two bolts on shock housing

Undo but do not remove top two bolts on shock housing

Remove bottom shock mount bolt then drop shock assembly down

Now the difficult part- you need to undo the shock mounting bolt. I used a spare 1/2" drive socket and ground flats on it so I could get a spanner on it whilst feeding a 1/4" socket through the centre.

More info here:

http://www.thesaabsite.com/95/FAQ--suspension-category--spring-and-shock-replacement-%28rear%29.html

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