'96 850 Turbo running rich, poor gas mileage

Post by **MadeInJapan** » 01 Jan 2008, 14:15

In the U.S. the GLT doesn't have a turbo until '97 (if my memory serves me right).

Post by **JRL** » 01 Jan 2008, 14:48

farupp wrote:I just noticed that MadeInJapan, in a post to lynetteyross on Dec. 31 about her '96 850 GLT, said: "About mileage- these cars differ considerably depending on how well tuned up they are and what kind of driving you do. Don't expect much more than 17 in the city but you could get up to the high 20's and even 30 on the highway if things are right with the car."

So maybe the 15 mpg is not out of line for around town driving. What are other getting as an average mpg for 850 turbos and non-turbos, especially around town?

Maybe I should do a poll.

Thanks for any input.

15-16 MPG is about right for around town driving with a Volvo turbo automatic, the NA naturally should get more mileage.
The highway mileage in a turbo automatic should range from 22-23 to 25 ish depengin on your foot.
Manuals get a heck of a lot better mileage

farupp · Post by **farupp** » 01 Jan 2008, 18:16

My son also drives our 850 turbo back an forth to school and puts in about $20 a week in gas. The computer says 15 mpg average, and an actual check I did by filling the tank confirms that is correct.

My Suburban gets about 17 mpg local, and 21 highway.

Thanks for the info.

Post by **MadeInJapan** » 01 Jan 2008, 18:32

If he wants to get better mileage and save gas, tell him to try driving for a week with the trip computer showing "instant mpg" and watch it as he drives. He'll find that there are many times he doesn't have to boost with the turbo and can let up on his right foot. I did this for awhile and was amazed....but after about a week I said, screw it and just went back to enjoying my car. Btw, my gas mileage is much less in the colder, winter months than during summer.

farupp · Post by **farupp** » 01 Jan 2008, 19:50

All true, MIJ.

Thanks.

farupp · Post by **farupp** » 30 Jan 2008, 07:56

I think I have located why my '96 turbo was running rich and getting poor gas mileage. Last weekend I replaced the front oxygen sensor, even though there wern't any DTC codes to indicate it was faulty.

When I removed the old one I also removed the extension cable that added about eight inches to the total connector cable length. I noticed that the pins in the extension cable connectors were slightly corroded. Instead of messing around with trying to clean the pins and reinstalling the old sensor. I just eliminated the extension and connected the new oxygen sensor cable to the original connector in the wiring harness. It was a little more difficult to connect, but this change (new sensor, taking out the extension) made a huge difference.

No more black exhaust when I first start the car! Gas mileage around town has gone up from 13 to 15 mpg to 20 and 21. On a short trip on the highway combined with some local driving I averaged 24 mpg. All highway driving should be even higher.

I even saw a momentary 99.9 mpg down hill at 55 mph. I think that is a high as the computer will register.

Question, I was told the extension cable on the front O2 sensor was added as a recall by Volvo. Mine is a Volvo cable. What was the purpose of adding the extension?

phoenix_iii · Post by **phoenix_iii** » 30 Jan 2008, 14:55

eh... they usually do not add parts like that without a reason... wire going near any exhaust/turbo/hot parts?

p3

farupp · Post by **farupp** » 31 Jan 2008, 05:02

No, the wire does not go near the exhaust downpipe. It does go over the steering shaft but adding the extension just made it flop around more, therefore more likely to get caught on something.

I think I've seen the extension wire mentioned on this forum before, but have not seen an explanation of why it is needed.

Maybe MIJ, Ozark Lee, or other regular contributor has an explanation.

All I know is my car now runs like it should so I'm not going to put the extension back on unless there is a really good reason to use it.

farupp · Post by **farupp** » 31 Jan 2008, 11:28

I checked on Bay 13 of the Volvospeed forum. This is what it had to say about replacing the front oxygen sensor and the extension harness (http://volvospeed.com/Repair/o2sensor1.php) :

"The new sensor has an added wiring harness/connector. This extra section of wiring is to help keep reference wires from clogging up with various engine deposits over time. When you get the new sensor make sure you have the extra wiring harness (it should be connected)."

I'm not sure how the wires clogging up with engine deposits over time would occur. All the wires (four) are protected inside an outer covering. The connectors on my extra wiring harness were corroded. From what I could see, all the extra harness did was add length and two more connectors (to go bad).

I replaced the front sensor and did not use the extra harness; everything works great. But, will I have a problem in the future, and if so, why?

Post by **Ozark Lee** » 01 Feb 2008, 15:43

Frank,

I found the reference to the TSB (NHTSA-2250010) but I can only get summary information by shelling out $45.00 to the National Highway Transportation Safety Administration or subscribing to Alldata.

Alldata was the biggest waste of money I ever spent on my daughters Porsche and I don't know if it is any better for Volvo models.

...Lee