posted by
someone claiming to be sevenvolvos
on
Wed Nov 28 11:38 CST 2007 [ RELATED]
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Group:
I am in need of informed opinions as to the possible causes of poor mileage.
I am convinced that my '98 S90 is running too rich.
Current mileage in suburbia with some 60 mile RTs on urban interstates and a few state highways is about 16 mpg on regular. Maybe a few 5 mile round trips as well.
Not cold in N Jersey with 40+ days.
One indication is that at a start, the engine seems to run rough even before the air pump starts. After warm up the engine is smooth again.
What are the possible things I could change, one at a time, to see any improvement?
Knock sensor? I can get one fron e-bay.
Coolant temp sensor? Don't know where it is located. Not the one that goes to the gauge.
AMM? Can get one off e-bay.
What else is there?
Consideration should be given to the difficulty of changing.
Items from e-bay can be re-sold at a later date if there is no apparent change.
Who can help?
-- S' V'
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Autozone will lend you an OBDII code reader to get and clear the codes that may or may not point to the cause of your problem. This you can do for free, but I'm not sure, the dealer may be able to glean more detailed information with thier proprietary equipment.
If nothing else, it would be good to clear any old stored codes, then drive the car to narrow them to the only codes causing your current problem.
Have you checked out the 700/900 FAQ for more info? Also, try http://caunter.ca/volvo960/ for more general information on the 960/S90/V90.
-Will
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850 / Mini
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posted by
someone claiming to be sevenvolvos
on
Thu Nov 29 08:42 CST 2007 [ RELATED]
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Will:
There are no codes stored, according to my local independent who has a very capable system.
I will look into the link you posted.
Thanks,
S'V'
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Hi, Why don`t you just take it to a Volvo garage to check the codes and fit the part that is causing the problem. Here in GB the petrol is at least twice your price and over a 6 week period of messing around with odd jobber garages decided to bite the bullet and went to Volvo. It had cost a fortune but the bill at Volvo was nothing compared to the rest. My problem was the o2 sensors and at 12mpg and rough running. I know this forum is more for DIY but when an expensive difficult to point out situation arises why not just get it over and done with and save money and inconvenience. The manufactures say between 60 and 100,000 miles is the good life of the o2 sensor. Mine were replaced at 99,000 it was the only single item that put my mpg back to 30mpg (2.5 European Model) Regards Keith
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posted by
someone claiming to be sevenvolvos
on
Thu Nov 29 08:47 CST 2007 [ RELATED]
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Keith:
Your info is good.
I am afraid the dealer will charge way too much.
My problem is not as severe as yours was, but I do have 120K miles..
I can have one o2 sensor replaced, and if that does not change anything I have a good spare for when one is bad. Or I put it in the other location.
Which one do you think has the most influence?
-- S'V' whose old '91 240 would be getting 20 mpg under these same conditions.
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Hi, The first o2 sensor has the most influence. Before my 960 went heavy on the fuel i was still only doing 20 mpg (with a 2.5!!!) After the sensors replacement 30 mpg To me that says if you have 120,000 on the clock of your Volvo, you are 20,000 over the maximum mileage that the sensors are any good for which is quoted by most manufacturers. So whatever you do unless you change them first regardless of non-codes you are winning a losing battle with your consumption. Don`t put second hand ones in, buy new ones and you will get what you paid for and don`t forget they will last about another 1000,000 miles! Regards Keith
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A vacuum leak would make the engine run rich, it is counterintuitive but what happens is the computer reacts to unmeasured air and richens the mixture.
I would check all vacuum connections, look especially at any rubber elbows, a missing hose that sort of thing. You definately are on the right track though, a bad temp sensor, a bad t stat, intake manifold leak, a tired 02 sensor. Some bad coils causing a miss, a bad amm as you mention. It might be worth having it hooked up to a dealer's scan tool, there would be clues on what to chase down for possible solutions. If it truley is running rich, the catalytic convertor could possibly be damaged over the long term.
Have you pulled a spark plug, are the black, before replacing parts some detective work needs to be done?
DanR '94 964 333,000 miles (99,000 on the new engine)
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DanR
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posted by
someone claiming to be sevenvolvos
on
Thu Nov 29 08:59 CST 2007 [ RELATED]
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Dan:
Good advice.
Plugs were replaced about 20K miles ago and indie shop said they looked good.
T'stat replaced 10K miles ago because the temp gauge did not get up to half way.
Indie shop showed me the failed unit and why it failed.
On the vacuum thing, last spring I pulled the hose off the fuel pressure regulator and it made no difference in mileage or performance. Big surprise! This is around suburbia and some interstate. High vacuum should lower the pressure and low vacuum should have raised it. Pulling the hose set the vacuum to zero. I would have changed it out but the indie mechanic suggested waiting. My car uses the expensive one.
All vacuum lines were checked at the time and found to be OK.
Maybe I will try the FPR replacement.
-- S'V'
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What DanR said (mostly).
The key is, you said it runs rough right from the start then runs fine when it's warm but the mileage is not so good. On cold start it's in open loop, the o2 sensors are still heating up so the the ECM runs your engine on a predetermined map based on coolant temp, air intake temp., etc... The ECM is not interactively adjusting your mixture and spark until all the sensors are online. That means, it is highly unlikely it is caused by an 02 sensor. Since your not showing any codes, that means that the problem isn't so bad that the ECM can't adjust. A scan tool should show you if your running rich in bank 1 or bank 2 or both. If the temp sensor (the one that feeds the ECM) has been replaced and is known good, I would bet it is a vacuum leak. These engines are known for them and EVERY single rubber item on that engine must be checked, carefully. You could have a intake manifold leak between cyls 1 & 2 like many of us have had.
DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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posted by
someone claiming to be sevenvolvos
on
Thu Nov 29 12:24 CST 2007 [ RELATED]
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Dan:
Ok, scratch the O2 sensor, maybe.
I am still unsure if it is a bit out of spec. Certainly not failed.
The temp sensor that communicates with the ECM has not been replaced.
I'm not sure where it is, but the local indie shop is very good on Volvos.
I will look into the possible intake leak and go through the hoses again.
Thanks,
-- S'V'
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Haven't been around for awhile but I wanted to jump in here also--As stated above-vacuum leaks will cause havoc with fuel metering--check and double check each vac hose--the little rubber boots on the plastic lines can look ok but still alow air by--check each line-not hard to do as a diy. The vacuum tree that all the lines come from has a rubber 0 ring I found a few years back-- It's held into the intake by a 10mm bolt. I just unpluged the sucker and used some sensor safe form a gasket and gluged her back in--no more leaks after that. The red intake gasket is crap--look between the intake and the head--if the gaskets red--change it out with the newer green gasket-you'll be glad you did--if you change the 02 sensor change the one before the cat--the one after doesn't do anything for fuel consumption. Another problem with these cars as the mileage builds on them is the thermostat that is located in the airfilter housing--that stat can go out and the only air that comes through the engine is hot air from under the hood--bad on mileage and the engine also--means that the cool air from out side the car isn't reaching the engine-most of everyone here has bypassed theirs. And lastly hello everybody-still miss my 960
Poolman
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posted by
someone claiming to be sevenvolvos
on
Thu Nov 29 12:37 CST 2007 [ RELATED]
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Poolman:
I will go thru the hoses carefully.
I will also check the color of the intake gasket.
My S90 has a very late manufacture date so maybe it has the good one.
Good advice on the T'stat in the airbox. I checked it several years ago and it was working. As I recall they fail in hot air condition.
Seems like that would improve my mileage.
I will check it again.
This poor mileage condition did not come on suddenly. It has existed for several years. Gas prices have stimulated my interest. It is possible that there is no problem with the car except it being a gas hog, compared with a 240. I have a very light foot.
-- S'V'
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"It is possible that there is no problem with the car except it being a gas hog, compared with a 240. I have a very light foot."
I too have a light foot and have repeatedly got in the high 29's with this car. Amazing for it's size, weight and performance.
DEWFPO
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1998 S90 077,400 and 1995 964 154,100
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posted by
someone claiming to be sevenvolvos
on
Fri Nov 30 11:52 CST 2007 [ RELATED]
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Dewfpo:
Your message and similar reports from others have caused me to open this thread.
My best was several years ago, mild weather, no A/C, 360 miles RT on interstate with no slowdowns, 70 mph max, and I got 23 mpg. The old 240 would have gotten 28+ on that trip.
I should mention that I use regular, but use premium when towing my trailer.
The difference cannot be that much with a light foot.
-- S' V'
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I did a study on which fuel to use over a 4 month period, the end result was the cars increased fuel mileage came to within pennies of paying for the higher octane. Low octane fuel decreased mileage, high octane increased it, they were nearly identical in total costs for miles driven. My driving consists of mostly urban, suburban driving, much bumper to bumper, lots of idling.
The only thing that might come into play with some people is that in extreme cold weather, the lower octane might be the better fuel for cold starts.
DanR '94 964 333,000 miles (99,000 on the new engine)
--
DanR
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posted by
someone claiming to be sevenvolvos
on
Sun Dec 2 07:37 CST 2007 [ RELATED]
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Dan:
What sort of mileage did you get on regular and on premium?
I have noticed that as gas prices go up, the differenial between regular and premium remains about the same. About 20 cents a gallon or about 7%.
If I got 7% better mileage, say 19 to 20.5 mpg or so it would be a wash.
Since I only have cold at 20F today I do not have extreme cold, and no cold start problems, that is not an issue.
I use premium while towing my trailer, only 1000 pounds but tall with wind resistance, I get 17 to 19 MPG. Always 300+ mile trips, some 3000 miles. Usually only in the better weather.
BTW, my S60 2.4T with IPD ECU upgrade, consistently gets better mileage in the same conditions as the S90.
-- S' V'
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He rally need to use High test gas in that ride.
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Ihad tried to operate my 960 on a lesser grade of gass and every time I tried the car wouldn't run well-I could tell the diff. With my son taking over-he tried to use a lesser gread of fuel and had the same out come. Check all those lines again and try the 91 octane for a few tanks-the knock sensors in your car can and will retard the timing and that'll mess with fuel mieage. Try it on a long trip-not to just kock around town.
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