Cadillac Owners Forum banner

1 - 20 of 42 Posts

·
Registered
2006 STS V8 1SF RWD
Joined
·
6,478 Posts
Discussion Starter #1
I've noticed over the last 2 weeks that I've been getting really terrible gas mileage in my '95 STS, and I'm talking bad, like a little over 200 miles on a full tank! I ran the diagnostics and it spit out P056 as the only current code and that's the trans. speed sensor, which in my mind would have nothing to do with gas mileage. I think it may be my catalytic converter though, my car bogs down at dead stop acceleration, and stutters a bit during hard accel at any speed, it also emits that stinky exhaust smell when she's givin "the nuts"....could this be my problem, or could it be something else? Any input would be greatly appreciated because it's getting to be kind of expensive to drive my car and I love driving this thing so I have to get this fixed and soon.....

Curtis
 

·
Registered
1989 Sedan DeVille is now just a fond memory ....
Joined
·
10,429 Posts
Always start with the basics first;

1. Has anything happened or changed two weeks ago or has this been gradual and that's jsut when you started noticing?

2. When was the last time it had a tune up? New plugs, clean the throttle body/EGR tubes, air filter?

3. All vacuum lines in good shape, no leaks?

4. Sometimes catalytic converters get clogged but that is usually very rare, happens when they break up and stop/slow the flow.
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
Catalytic converters emit a rotten egg smell sometimes when they are crapped out. Check your ignition system components like plugs,wires and also check your egr. Throttle body clean up is easy and should be one of the first things done.

Just like Kev said.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
I believe a rich fuel condition will cause a rotten egg smell. Check the FPR, a common cause of poor fuel milage.
 

·
Registered
2006 STS V8 1SF RWD
Joined
·
6,478 Posts
Discussion Starter #5
well since i got the car it's always ran a little rough, but it really hasn't been all that noticeable until as of late. my gas mileage wasn't too bad, around 15/22, which is acceptable. my fuel pump went out about 2 months ago so i replaced that along with the filter, change the oil when the car tells me to do so, but now something is really wrong with it...as to the the rich fuel comment i was told once that my exhaust kinda smelled like maybe the engine was running a little rich. well ill take a look at some things and get back to all of you...

curtis
 

·
Registered
1996 Cadillac STS
Joined
·
85 Posts
i have a 1996 sts and im geting 260M for 3/4 tank this is bad as whelli asume i just got the car im not relly whell aquainted with the car yet it just seamses bad to me but is it?
 

·
Registered
2006 STS V8 1SF RWD
Joined
·
6,478 Posts
Discussion Starter #8
I would kill for gas mileage like that! right now my odometer is around 150 or so and I have a little more than a 1/4 tank left, it guzzles gas! :alchi:
 

·
Registered
Joined
·
1 Posts
i had this same problem with my 95. car was riding rough and getting about 190-200 miles on a full tank of gas.......

i took it to the shop and they replaced one of the ignition coils and this fixed everything...car is running smooth and im now getting 350-400 on a full tank.

and this was a cheap fix cast me like $100
 

·
Registered
'94 Seville STS
Joined
·
68 Posts
My '94 has been getting worse gas mileage lately. Although, letting it sit and warm up for a minute or two doesn't help. :)

My milage has gone from 22.5MPG and a range of 425 miles, to 16.7MPG and a range of 340 miles. The first thing I'm going to check, (and would check on yours as well), is the FPR. They are a very common problem, but they are an easy fix.
 

·
Registered
Joined
·
108 Posts
Have you checked the really, painfully obvious? Clogged air-filter? This includes a clogged duct going to the airbox - which could have ingested leaves, a plastic shopping bag or other "stuff" (or, if the car sat for a bit perhaps a mouse built a nest?) - you might laugh - but a friend of mine bought a "barn fresh" Indian motorcycle some years ago - we put some gas in the tank and started kickin' it over - we got this really loud backfire as a mouse nest and what was left of a mouse or two shot out of the exhaust pipe and splattered itself on the garage door ... I've pulled mouse nests out of air cleaners before as well ...
From there I'd look at the condition of plugs and wires - then I'd head to the more complex (expensive) stuff -

Steve
 

·
Registered
94 Eldorado, and a 99 ETC
Joined
·
3,887 Posts
I think you should fix your speed sensor.

With a bad speed sensor the computer will engage the TCC (Torque Converter Clutch), and disable torque management. This will put more load on the engine at low speeds which could cause it to spudder and make it hard to keep idle speed. With the extra load, the engine would require a little more gas to help it turn over.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
SteveThefolkie said:
Have you checked the really, painfully obvious? Clogged air-filter?

Steve
A dirty air filter will not affect gas milage on a computer controled, fuel injected engine like it would on a carburated engine.
 

·
Registered
2006 STS V8 1SF RWD
Joined
·
6,478 Posts
Discussion Starter #15
Krashed989 said:
I think you should fix your speed sensor.

With a bad speed sensor the computer will engage the TCC (Torque Converter Clutch), and disable torque management. This will put more load on the engine at low speeds which could cause it to spudder and make it hard to keep idle speed. With the extra load, the engine would require a little more gas to help it turn over.
would this explain why my engine bogs down from dead stop acceleration, the computer isn't letting the engine let loose it's full potential? But with the spuddering issue, it doesn't just happen at low rpm's, it happens pretty much whenever I accelerate at a decent pace, also if it's any help, the engine doesn't seem to respond to the gas pedal like I think it should, it's like there's somewhat of a delay and I have to really push it down to get any kind of decent acceleration but usually by then shes opened up pretty wide. it's like there's no "in-between", its either you're lightly cruisin or it's roaring, if i try to just accelerate a little it just won't do it, the engine starts to sound "muffled" in a way, but then once I get passed a certain point she just takes off, its really wierd and it's buggin the hell out of me.....
 

·
Registered
94 Eldorado, and a 99 ETC
Joined
·
3,887 Posts
Yes it is most likely why the car is bogging down. Your car will likely not bog down at speeds over 40mph because thats when the TCC is supposed to engage under normal operation. It doesn't fully engage at the lower speeds because that would stall the engine, but it does engage.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
I think a bad TPS will also cause it to bog down from dead stop acceleration.
 

·
Registered
2006 STS V8 1SF RWD
Joined
·
6,478 Posts
Discussion Starter #18
ok, so far it could be...
- FPR
- clogged cat
- plugs & wires
- TPS
- or who knows what :)
or a combination of them, would any of these things cause my SES light to come on only when below 1000rpm and it go off a little after the car shifts into 2nd? The shift into 2nd can be a little rough at times too, but the rest of the gears shift fine....the wierd thing is is that at random this rough 1st to 2nd shift issue will completely go away and my SES light will not come on, but that usually doesn't last longer than one or two stops...This damn car is so confusing, I'm glad I own one of these beautiful machines but she can sure be a pain in the ass sometimes....reminder that it does throw the P056 code (trans. speed sensor) currently but that's it.......
 

·
Registered
Joined
·
5 Posts
I have a 94 Eldorado that I love for its performance but not necessarily for a smooth ride. I have made frequent trips from Baltimore to Goldsboro,NC and it takes me every bit of a tank.That is about 357 miles but I drive at about 80-90 mph on road trips.
 

·
Registered
13 Challenger RT, 11 CTS Coupe Premium, 94 Eldorado (RIP)
Joined
·
1,306 Posts
Filled up my 94 Eldo yesterday. Range went to 410 upon fill up.

I have had compliments on the smooth ride of mine. Ofcourse, this was from the owner of a 98 Camaro. The Eldo's ride would be much smoother than that.
 
1 - 20 of 42 Posts
Top