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Discussion Starter · #1 · (Edited)
Lately, my 96 900S has been getting crap for economy on the highway.

At 70, it barely does 26MPG, 65 right around 28.

This seems to have happened recently. Before, I would get almost 35MPG at 65MPH.

I just did plugs (they had 60K miles on them), replaced the old NGK's with Bosch Plat. +4's.

I was also talking to a SAAB tech who said that he has seen some thermostats that open too soon. The temp gauge would still show right, he said, but the engine would be too cool.

So, I replaced the T-stat with the highest temp I could find (195F).

So far, it still seems to be consuming fuel at a higher than usual rate.

Could it just be winter gas? (Do they even use winter gas in South Carolina?)

More info about engine:
The engine was rebuilt at 110K miles, now has 170K miles.
Head shaved to SAAB max spec.
Oil is Mobil1 0w40, changed religiouly.
Fuel is BP premium. Sometimes I add in Lucas Fuel System treatment (awesome stuff).

The only thing I can think it would be:

Coolant temp sensor, MAF sensor, or front O2 sensor. All of those were not replaced when I built the engine.

There are no DTCs in the ECU.

All help is appreciated.

[EDIT]

Now that I have had time to shower now that I have gotten off work, I realize now that the fuel economy dropped to the current mileage after I repaired my PCV system.

The large diameter hose going to the "valve" was incorrect and the grommet in the valve cover had broken off. This was causing an odor.

After replacing the parts, the odor was, of course, gone, but fuel economy was notably lower.

Should I just induce a leak in the intake after the MAF to bring my economy back up? :cheesy:
 

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KLowD9x said:
The large diameter hose going to the "valve" was incorrect and the grommet in the valve cover had broken off. This was causing an odor.

After replacing the parts, the odor was, of course, gone, but fuel economy was notably lower.

Should I just induce a leak in the intake after the MAF to bring my economy back up? :cheesy:
Now that's a new one for me. Are you saying that the larger diameter hose going to the valve cover caused you to have a "vacuum-low" condition that positively affected gas mileage? How would that work? (seriously, not trying to be a smart-*****)
 

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Frank_Drebin said:
How would that work? (seriously, not trying to be a smart-*****)
Something was making the engine run rich. Prime suspect on an older 900S would be the MAF (cleaning instructions for that are here somewhere) The leak made more air go into the intake at vacuum, making it run leaner. Leak fixed: engine back to running a tad rich.

It might be as simple as resetting the ecu. I don't know just how adaptation works on the "S" model with the Bosch Motronic ecu, but the turbo models with the Trionic ignition need a reset under some conditions.
 

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On stop and go with idling and mixed driving I'm getting 25 mpg (give or take).
Consistent speed driving over 30 mpg and as much as 32 mpg.

My car is a 97' 900S 2.3 n/a auto with 142.5K.

I'm not sure if that is typical or not.

jmcg
 

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banolte said:
according to the sid on my turbo, i am only getting 18 mpg. my na 900 gets 28 mpg. is that normal?
We average 27.5 city driving and 30+ Highway. When my turbo started blowing oil into the intake recently I noticed a drop to 24.5.
 

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banolte said:
according to the sid on my turbo, i am only getting 18 mpg. my na 900 gets 28 mpg. is that normal?
No. Not unless the turbo spends most of its time in stop and go traffic.
 

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I dont know why some are expecting their saabs to be 40mpg cars...

I just looked at my window sticker from the dealer ('95 900s 2.3l n/a) - mpg expected -

16-18 city / 24-26 hwy
 
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