'99 Olds Intrigue w/awful MPG need help!

Hello group.

I've a 1999 Olds intrigue (3.5l/94K) that's been getting awful fuel economy for some time now and nothing seems to help. For the first year or so I owned it, it consistantly got 19-20mpg in all city driving. For the last 1.5 or so years it has dropped to 14-16mpg, usually closer to

  1. As soon as I noticed the huge difference at the pump, I started having work done but nothing's changed. Thus far I've had new platinum plugs put in, a 0 fuel system cleaning, tires rotated and balanced and I've run some chevron techron thru it. I also get regular oil changes w/mobil1 and just had the tranny fluid changed. I check tire pressure often and drive pretty conservatively.

People have suggested the next thing I should try is replacing the oxygen sensor, but both mechanics I've asked about it seem to think it would be a waste, and that without a check engine light it's probably working okay.

So really I don't know what to do, but this problem is driving me nuts! I gotta think that something is going very wrong, but not knowing autos very well, or being a DIYer I have to rely on the mechanics. Is there some kind of diagnostic machine that can find the problem?

Aside from the awful mileage problem, it's been a pretty good car. I'm just getting so frustrated with this that I'm thinking of trading it in. Thanks in advance for any suggestions!

Reply to
gw1894
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There is a recall on some of them because the heater hose hits the O2 sensor hard enough that it can even puncture the heater hose. This might also do bad things for the O2 sensor or it's connections.

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Some engines run like crap on platinum plugs also....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Well, if you *will* drive a car with an enormous engine and fuel-wasting automatic transmission... Maybe when fuel in the US starts to be taxed at the same rate as in the UK, there'll be the same incentive as over here to buy a more efficient car.

Reply to
Martin Underwood

I would have thought that a mechanic could hook up their diagnostic machine while the car was running and tell if there is a problem that would cause the vehicle to run rich.

Reply to
marks542004

"Martin Underwood" wrote in news:458c233a$0$8723$ snipped-for-privacy@ptn-nntp-reader02.plus.net:

the old 'ugly american' diagnosis......hmmm, doesnt really address the problem of mpg falling but i dont imagine that was what you wanted to do anyway.

Reply to
KjunRaven

When you have to pay our pump prices, you'll see that driving a vehicle that does as little as 14 mpg (17.5 miles/UK gallon) is going to be VERY expensive.

UK prices are currently about 88 pence/litre for petrol (gasoline) and 90 pence/litre for diesel. There are about 3.6 litres/US gallon, and the exchange rate is currently about $1.96 = £1, so that gives prices of $6.21 and $6.35 respectively.

For the record, my car has averaged 50 miles/UK gallon (40 miles/US gallon) over the seven years I've had it - that's for a 2-litre diesel.

Maybe one day the US will learn to curb its profligate waste of fuel.

Reply to
Martin Underwood

Now that gas prices have leveled off, Ford Excursions with V10s and the like are popular again. I drive an 06 Honda Accord I 4 -- which is just fine for me with plenty of power and decent mileage around 30mpg mixed. But, most people love their big SUVs even though they get around 10-14 mpg -- with just one person in them going to work. The U.S. has a huge challenge in coming up with a decent energy policy that will reduce the need for huge imports of foreign oil. I very doubt that any polititian will want to take that on.

Reply to
tww

It seems you have the fuel system sorted if that has been cleaned, the plugs would assume the electrics are running perfectly. What about the vacuum system? I'm not familiar with the model, being down in australia, but i do believe a vacuum leak can result in spark not being advanced enough, which could be throwing the fuel management system haywire. Are you noticing any loss of performance? If it takes more gas to accelerate the car than usual the problem may be as simple as sticking brakes or clogged air filter. Speaking of which, the air intake sensor may be playing up, making the ECU compensate for what it thinks is a huge quantity of air coming into the engine by adding more fuel. I'm not a mechanic, and i dont claim to be familiar with your problem, but at least this advice may help in some way shape or form. Case and point, stop using this group to argue which country has better choice in vehicles, it hardly fixes the problem at hand Hope these suggestions help

Reply to
Josh

If I was going to just guess at what the problem could be I would start with a MAP sensor. I have seen them fail several times and cause this problem but no be far enough out of spec to set a code.

Steve B.

Reply to
Steve B.

The simplest thing I can think of is to have the compression checked at each cylinder, and make sure air cleaner isnt restricted. Low compression do to worn rings or valves would cost you power and fuel economy.

Pete

snipped-for-privacy@hotmail.com wrote:

Reply to
conan

A) 3.5 liters is hardly "enormous" B) Automatic transmissions have been more efficient than manuals since the early 90s when they became computer controlled so that all fuel wasted during shifts is no longer wasted, and torque convertors are locked in all gears. C) Here's a nickel. Buy a clue.

Reply to
Steve

So vote your over-taxing government out. That's where all your fuel cost comes from, not from the fuel itself. Hell, 50% of *our* fuel cost is nothing but tax, and its still more sane than yours!

Reply to
Steve

Oxy sensors will get sluggish in their response and start cutting into fuel economy before they get bad enough to trip the OBD and set the light. But I'd have it put on a diagnostic scope and checked for other things, too. Temperature sensors (coolant temp and inlet air temp, for example) out of whack can result in the wrong fuel curve being used by the computer. A MAF sensor out of whack can waste fuel. A vacuum leak can waste fuel. An EGR system not working right can waste fuel. A bad knock sensor can erroneously cause the computer to run with the timing retarded all the time. Etc.

Reply to
Steve

Having learned to drive in a car with about 1/5 the displacement, I have to say that's enormous by the standards of much of the world.

People keep telling me this, but I am still not sure that I buy it. I'll admit that modern automatics are a lot more efficient than they used to be, but by they same token they take a lot more energy to make in the first place as well.

--scott

Reply to
Scott Dorsey

Owning one 3.5L car and two 7.2L cars makes me think otherwise ;-) Granted, 7.2 Liters *is* enormous and impractical for a modern vehicle... but MY what a lot of fun in old cars! Yeah, some small modern engines equal or exceed the peak power ouput, but instantaneous torque in any quantity you want just can't be duplicated without displacement.

Well, its hard to get a fair comparison anymore since so few cars are still offered with manual transmissions these days. But in cases where the same car/engine combo is offered with both, there's often a mileage advantage for the auto, particularly in city stop-and-go driving.

I'm not sure I follow- why do they take more energy to manufacture? An automatic is actually a very simple machine (mechanically speaking) with no more moving parts than a manual (and potential for much greater longevity, since the gears are in constant mesh, there are no hard metal-to-metal clashes during shifts, and the friction materials operate in a lubricant bath instead of the stone-age dry clutch of a manual transmission.

Reply to
Steve

Just wanted to say thanks for all the suggestions. I'm not too knowledgeable about the cars, but I'd have thought diagnostics could be done to find the problem as well. I've taken notes and will be calling around to hopefully find someone who can fix the problem. Don't know why the last 3 shops (including a GM dealer who suggested my tank was filling to diff. levels w/ diff. pump nozzles, despite the fact I calculate MPG after each fill up) haven't been able to address it.

To the UK guy; obviously I'm not happy with the poor fuel economy. This is my first car with any power. My two previous cars were an '82 Sentra and a '90 Dodge shadow, both of which did much better with the gas. However, I live in a hilly area and part of the reason I wanted a V6 is so's I'd be able to go up them. MPG was a consideration when I bought the car in spring of '04 and 19/27 was pretty good for a 6cyl. in my price range. As it happens I do support conservation, take the bus to work and have put less than 10K miles on the olds in the last 2.5 years. When it's time to buy my next car, I'll probably look for a 4 cyl. with some balls.

Thanks again y'all and have a happy new year!

Reply to
gw1894

For the "record", I also own an Intrigue with the 3.5. I get mid 20's MPG in mix of stop and go, errands/short trips, and some highway. On a road trip after I got the car out of state last spring, I got 33mpg highway one tank, 32 mpg the next, and 29+ the next (decreasing speed enforcement as I went south and then AC needed to be used in south accounting for change).

If you compare this vehicle with "economy like compacts" such as Chevy Cobalt (24/32), Ford Focus (27/34), Mazda 3 (25/31) or many other similar vehicles, their MPG is not much different. Granted, city milage will be the biggest difference, but if you really look hard at the numbers you can see that in many cases, there is not a MPG based reality to buying a smaller car.

My Intrigue has tons of power in reserve, doesn't downshift at all on hills. The automatic is incredible, it really shifts great and has converted me from a manual lover. No longer is an automatic a power hogging slush box. My car also has tons of features like stability control, heated seats, dual zone climate, etc etc and while its bigger than a Mazda 3, it gets about the same MPG. Heck, I had a '88 Shadow that wouldn't get over 27mpg no matter how you drove it (turbo /

5speed) and it was tiny in comparison.

While I support cars that get good MPG for the sake of the diminishing resources and environmental impact, with the current mix of vehicles in the US, many mid/large cars can get the same MPG as smaller ones.

Scott

ps. I even used to own a Ford Tempo Diesel 5 speed, and that would get

44mpg average, but what a POS car!
Reply to
scott

We just got a 99 Intrigue 3.5 V6 as well. the mileage has been 18-19 MPG and that seems low compared to my 97 grand voyager (its in the shop) it has a v6 3.3 but is much bigger and gets around 22-23 MPG on average in the same driving conditions. I am not satisfied with the MPG on the intrigue. I will be checking back to see if you come up with a fix.

Just my two cents as well, I owned a 93 saturn sl2 5 speed that got great gas mileage (around 33-35 MPG) before I had kids. I loved the car, but it didn't have enough room for us and what we had to carry with us. Sometimes the smaller cars are just not feasible for a family. I don't think any of us are looking to deplete resources, we are looking to keep our families safe and comfortable while in the car.

Reply to
3kbugs

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