850 Turbo Gas Consumption < 14 mpg

mc2prod · Post by **mc2prod** » 02 Jan 2011, 12:09

Hi all.

I have search the forums for some solutions to my stock 1996 850r (Turbo) wagon's gas guzzling problems. I wanted to see if there is any other ideas of how to improve gas mileage.

Note: Please post only if you have had this issue previously and resolved it. Its not helpful to post how great your 850's gas mileage is. I have seen this is other posts on this issue. I have not seen where someone has had this problem and come back and said it is resolved.

To try and resolve this issue, I have already done:

1. New spark plugs, distributor cap, and wires (Old spark plugs did not give an indication of burning excessive fuel or oil)
2. New Mass Air Flow Sensor (MAF)
3. Transmission TCU from an NA (mild improvement)
4. Swapped out fuel rail, injectors, and fuel pressure regulator
5. New Fuel Filter
6. Cleaned Throttle body
7. Dialed down the turbo by adjusting the wastegate (6 full turns - much improved on the highway: from 16 mpg to 21mpg)

I put in a rebuilt turbo that has plenty of boost. Obviously that might be a problem.

Please any help from those 850 turbo owners that have had this issue and resolved it or know someone who had the issue and resolved it, please post!!! If I cant resolve this issue, I am going to sell the wagon.

smiles855r · Post by **smiles855r** » 11 Jan 2011, 17:48

Had a similar problem right after purchasing my 96 855R a year ago and found that the fresh air vacuum line had come unconnected from the nipple just under the MAF sensor. Hope that helps

Post by **jblackburn** » 11 Jan 2011, 23:53

Before you go about throwing any more parts at it, absolutely look for cracked or missing vacuum line connections - that would be where I'd suggest you'd start. The brake booster hose might also need to be replaced - mine is beginning to visibly crack.

Does the exhaust smell rich? Do you have any O2 sensor codes? If you eliminate everything else (vacuum lines, turbo air leaks, etc.) it might be time to spring for a new O2 sensor. My gas mileage was taking a slow decline at around 160,000 miles, and after I had eliminated most other causes, I took a gamble and put in a new front O2 sensor - back to high 20's mpg figures.

The rear O2 does not really do anything but monitor the catalytic converter, so if you don't have any codes for it, leave it be.

If you turned down the turbo that much, do you have any power at all anymore? I left the nut too loose on mine after making an adjustment to it and it backed itself way off, and the car just felt like a pig to drive.