fuel mileage and rpm question

[03glgold]

I tried using an existing thread but got no replies...for a while now (since about mid-september) my car has been showing steady declines in fuel mileage, it has also been pulling higher rpm to hold speed than normal, though I can coax it to drop for a while and sometimes if I go straight to the highway after a particular bout of being racy (lots of hard quick acceleration with no speed maintenance) it will do it on it's own until the next time I shut it off. I have log files that I took using torque that I will add in, I highlighted in yellow going 80 down the interstate, in green an area during that time when I made it shift to the right rpm for a bit, and in red a quick 80-100 pull to show what it did under stress (I was very alone at the time) I hadn't realized until afterwords that it was set to record every second so it is a long file and that is part of why I picked it apart. The first highlighting is on line 456, I left it all there to see if there was anything else that might help outside of it, at the end of the log I was sitting idle

https://drive.google.com/file/d/0B_n...it?usp=sharing new link in lower post

[MMGT1]

link not working

[03glgold]

link not working

i will have to fix the link at school tomorrow so that I can use my laptop without having https restricted (only have tethering)

[a.graham52]

How's the basic tuneup? If your engine is skipping it won't allow your torque converter to lock. One of MANY possibilities.

Frankly I want more info about your car. Condition, maitnence history, overall performance (how well it's running, not mods).

[03glgold]

173400 miles, I change the oil every 3-5k miles since i got it with 134k though it wasn't the best maintenance before I got it. Plugs were replaced around 140k along with plug boots, timing and balance chain assemblies were replaced at 152,737 miles due to the tensioner starting to fail. It overall runs good, however there has been a sound i have attributed to noisy power steering pump, though power steering is now working smoothly after a fluid change with some conditioning additive, there has been a slight chirp from the passenger side the past couple days while it is really cold (cold startup under 10 degrees). I have considered trans fluid change it was last done at 90k miles however almost all of the miles I have put on the car have been highway miles. I have been getting better overall performance as of late than ever since i bought it but looking at things it is still not putting out what a properly running ecotec should be doing.There is however the occasional stumble at idle where it will bounce between about 400 and 600 rpm before settling out at normal idle. It has all original sensors with the exception of the IAT sensor. I am lead to believe it is a sensor issue with my primary suspect being the throttle position sensor but don't want to start guessing throwing all sorts of sensors at it and go through all that money to find a problem when someone has a better answer than me.

[03glgold]

here is a new link...if it doesn't work then let me know and if you want to view it give me and email address and I will send it directly to you. I would download the link because the back part of the table is cut off when just viewing on google docs
https://docs.google.com/file/d/0B_ne1eiQbb25VGwxakFIYnRucFk/edit?pli=1

[zzyzzx]

I also suspect you have torque converter issues. Check for codes! Transmission codes don't necessarily light the dash light. I don't know for sure on an Alero, buy on my other car it definitely does not, since it's not emissions related.

[03glgold]

I check codes there is nothing

[zzyzzx]

I would be checking that the A/C compressor wasn't somehow on, even in this weather. Given the intermittent nature of the problem, it may take several attempts to verify this.

[03glgold]

I can check that...i wouldnt think it would cause it as it used to run 2900 rpm even with ac on at 80 and it now wants to go 3300 rpm...i suppose if it isnt shutting off and losing a bearing or something it might cause it though...i forgot t mention in the post about running condition that it does occasionally do the ecotec thing where it sends some oil through the breather and i plan to pull the intake manifold to see if the pcv port in the manifold is clogged

[03glgold]

Here is a youtube video to show how it is naturally going and how i have to get it to where it should be
_OLdGp4STp0

[a.graham52]

says video is private. but a 400 rpm difference suggest the torqe converter not locking. either commanded or a failure.

[03glgold]

What type of issues could cause commanded...i have to believe it to be more likely commanded as this is how it operated before the chain and it operated properly for about a year and 15000 miles before starting to do it again plus the fact that the tables get to around 75% load before it does it...timing advance at around 80 is running above 20 degrees which seems really high to me...the table and video should be fixed

[zzyzzx]

I am still thinking that the torque converter is not locking. Try testing the solenoid externally.

I just replaced a bad transmission shift solenoid on another car, and it wasn't too bad:
http://www.feoa.net/threads/how-to-replace-1-2-shift-solenoid-on-atx-1991.82837/

[03glgold]

I have to add a little more that i discovered yesterday...Where I originally thought it was driving it without holding any one speed then going on the highway that effected it I discovered yesterday that the reason I thought that is because most of the time I drove 70 down the highway to a town over and got gas before getting on the interstate. Paying attention yesterday I discovered that it works perfectly at 70 regardless. At 85 it is a lot easier to get locked in at 80 and it stays locked for longer before messing up again. My car is dumb

[MMGT1]

Alright bud, think I have an idea now I've seen that vid. Behind your brake pedal there are two switches. They are both white and both are adjustable.
I will try to describe the repair as best as I can here for you....


Remove the 2 sections of plastic panels that cover the area under the steering column. This includes removing 3 7mm screws and a plastic flare plug.
This will give you access to the 2 switches as you see in the pictures below
Disconnect the wire harnesses from both switches
Remove the upper switch (brake switch) by twisting 1/4 turn and test with ohmmeter on the harness contacts to ensure proper switch functionality. There are 2 sections to this switch, so check each accordingly with the ohmmeter.
Reinstall brake switch*
Remove the lower switch in the same fashion as the brake switch (this is the TCC Switch), and disconnect the wire harness. Test with ohmmeter for proper switch functionality.
Reinstall TCC switch*
Plug in wire harnesses to corresponding switches...don't worry, they only fit one way so you can't mess them up.

*Here's the important info you need to know...this is what fixed my problem:

When reinstalling the 2 switches, slightly depress the brake pedal with one hand while inserting the switches and twist 1/4 turn to seat them properly. You will see a sort of thread on the 2 sides of each switch that actually allows you to seat each switch at the desired depth. Make sure that both switches are seated and protruding the same distance from the bracket...this ensures both are completely depressed when the brake pedal is released. See the second picture below to see the properly seated switches while they are fully engaged by the brake pedal. The first time I reinstalled them I wasn't careful enough and they weren't close enough to equal, so I had to do it again. The second time, there was sufficient pressure to engage both switches properly and no more problems!

http://i823.photobucket.com/albums/zz159/MMGT1/EngagedSwitches_zps349bb683.jpg

http://i823.photobucket.com/albums/zz159/MMGT1/ReleasedSwitches_zpsc2692da5.jpg

[03glgold]

I went and tried that...it took all of maybe 5 minutes to do and it seems to be working fine...never would have begun to think of anything like that...I am sure the rpm issue will fix at least some of the mileage and i bet a lot of the rest is in me needing to clean the pcv port in the intake manifold to hopefully finally stop it from throwing oil through my breather and hopefully I will have all my mileage back

[MMGT1]

Did you test the switches with an ohms meter though to ensure they are functioning properly? That video is a carbon copy of what happened here.

[fisdad]

I get crappy mpg with the 2.4. 18 city, 28 hwy and 22-24 combined.

[zzyzzx]

Isn't it easy enough to check your brake switch by checking your brake lights?

[MMGT1]

Not doing 80 down the interstate its not! LOL And its the Converter switch that is more important, both those work together there

[03glgold]

Did you test the switches with an ohms meter though to ensure they are functioning properly? That video is a carbon copy of what happened here.

I was going to but the battery was dead...I will check it at some point

[zzyzzx]

Not doing 80 down the interstate its not! LOL And its the Converter switch that is more important, both those work together there

You mean the brake light switch is a double pole switch?

[03glgold]

There are two switches there

[mastershake]

also remember that we are now on winter blend fuel. (you guys do that too, right?) my mileage has dropped from 26 to 18 (mixed driving) over the last 2 months.

[zzyzzx]

There are two switches there

That's what a double pole switch is. On my other car there is one switch which is used by everything.

[MMGT1]

That's what a double pole switch is. On my other car there is one switch which is used by everything.

You got it. But, I cant remember which is the brake and which is the TCC. You could depress each individually and see which one activates the brake lamp and then test the other is the best I can come up with.

[zzyzzx]

You got it. But, I cant remember which is the brake and which is the TCC. You could depress each individually and see which one activates the brake lamp and then test the other is the best I can come up with.

If you can depress either one, then that's two single pole switches.

[S8track16]

MMGT1, Can you update the photos in your original post, I seem to be having a similar issue and would like to try this.

[03glgold]

If you have to replace them do both...i only did the inboard side and it only fixed half the problem...new ac delco from the stealership is under $20 a piece so really not worth the extra time

[S8track16]

It turns out that my problem was the A/C being on without the light working, so as soon as I turned it off, everything was shifting normal again.