Sudden FE drop - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 08-28-2007, 02:50 PM   #1
Registered Member
 
s2man's Avatar
 
Join Date: Jun 2007
Posts: 123
Country: United States
Sudden FE drop

I've had ~20% drop in FE recently on my last two tanks. I'm currently blaming some gas from a strange station, since that purchase sort of coincided with the change. But I have doubts on about that being the cause...

The engine is idling great - so smooth I have to look at the tach to see if it's running. But I feel some hesitation/stumbling during acceleration and cruising. I don't have exact TPS numbers, but my foot-o-meter says it is taking more throttle to do everything. Everything else, like temps, trannie, tires are normal. And I've made no mods lately.

Can you guys think of anything else that could cause a sudden change like this?
__________________

__________________
Roll on,
S2man

s2man is offline   Reply With Quote
Old 08-28-2007, 05:43 PM   #2
Registered Member
 
brucepick's Avatar
 
Join Date: Feb 2007
Posts: 722
Country: United States
Location: Connecticut
Check vacuum hoses too.
They like to get cracks, especially near the ends where the connectors are.

Also check thermostat. If you know what your upper radiator hose normally feels like, grab it when it's idling fully warmed up and see how it is. My rule of thumb is, if you can grab and hold on and keep your hand there, the t'stat is letting it run too cold.

Oxy sensor can also go bad. Testing needs a voltmeter. If it's a simple 2 or 3 wire sensor you can look up the procedure on the web, just google for it.
__________________

__________________
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
brucepick is offline   Reply With Quote
Old 08-28-2007, 06:01 PM   #3
Registered Member
 
Join Date: Jan 2007
Posts: 104
Country: Canada
A slippery clutch, since you did not mention it specifically in your post? Just my random thought.
swng is offline   Reply With Quote
Old 08-28-2007, 06:34 PM   #4
Registered Member
 
Join Date: Mar 2007
Posts: 1,138
Country: United States
Maybe the station had e85 in its tanks instead of gasoline?
__________________
Bill in Houston is offline   Reply With Quote
Old 08-28-2007, 06:37 PM   #5
Registered Member
 
mrmad's Avatar
 
Join Date: Mar 2007
Posts: 386
Country: United States
You might want to jack the car up and spin the wheels by hand to make sure your brakes aren't dragging. It also could be that your catalytic converter could be clogging up.
mrmad is offline   Reply With Quote
Old 08-28-2007, 06:49 PM   #6
Registered Member
 
psyshack's Avatar
 
Join Date: May 2006
Posts: 443
Country: United States
All great suggestions.
__________________
09 HCHII, w/Navi
07 Mazda3 S Touring, 5MT
Mild Hypermiler or Mad Man?
psyshack is offline   Reply With Quote
Old 08-29-2007, 05:03 PM   #7
Registered Member
 
Join Date: Oct 2005
Posts: 1,978
Country: United States
Drop here too

For me it has been the heat. I had a great 40 mpg tank, then ka-pow: A/C use, extreme temps and a miserable 30 mpg tank. The latest is around 34 -- close to usual, but still not as good as what I was getting.

For me, routine maintenance is overdue: oil change, air filter, etc.
Additional maintenance pending: Leaky valve cover gasket, A/T fluid change.

Here's the biggest problem lately: the school traffic pattern. Leaving at the same time as I usually did, I now get stuck behind buses, additional traffic to high schools (and not the best of drivers either), and the highway is more clogged-up -- theory: parents dropping kids off at the same time and hitting the highway in a big clump.

If these don't apply, then the other suggestions so far are quite valid. Dragging brakes especially are a biggie.

Have you tried resetting the ECU? How are IAT's lookin'?

-Rick
__________________
rh77 is offline   Reply With Quote
Old 08-29-2007, 07:08 PM   #8
Registered Member
 
Join Date: May 2007
Posts: 447
Country: United States
I just posted a really bad 35mpg tank, and I though WTF? My coasting distances have been shorter. So I started checking, and one of my brakes was dragging. I loosened up the caliper, and I can feel the difference! I know it needs replacing, but this has to last for a few more days. Maybe then I can hit a 40mpg tank!
__________________
slurp812 is offline   Reply With Quote
Old 08-29-2007, 07:19 PM   #9
Registered Member
 
Join Date: Aug 2007
Posts: 313
Country: United States
The best thing is a great empty rolling spot where you know how far you should go... kind of like toboganning.
__________________
2TonJellyBean is offline   Reply With Quote
Old 09-04-2007, 02:11 PM   #10
Registered Member
 
s2man's Avatar
 
Join Date: Jun 2007
Posts: 123
Country: United States
Thanks much

Quote:
Originally Posted by psyshack View Post
All great suggestions.
Thanks, everyone. Water and IA temps are running normal; low 200's and 110 when ambient temp is in the 90's. No clutch - automatic, which seems to be working normal. I replaced the O2 sensor this summer, and reset the ECU. Mileage improved after that, until recently.

I have the tune-up parts, but I've been sick for a couple of months and haven't had the energy to do many mod's. I also bought a new wheel bearing last weekend. I hope to get under the car this week. I'll let you know what I find. I will check the brakes when I have the car up on stands. I'll also check vacuum hoses. I haven't smelled it, but I'm gonna look at the gasoline lines while I'm under the hood too.

Thanks again for the help,

Stew
__________________

__________________
Roll on,
S2man

s2man is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
RSS feed for Fuel Tip Page randomic Fuelly Web Support and Community News 3 08-22-2008 11:55 PM
GasSavers.org Stickers Matt Timion Fuelly Web Support and Community News 7 10-12-2006 04:48 PM
FFI GasSavers_MPGmaker Introduce Yourself - New member Welcome 39 05-30-2006 04:31 PM
Where to get parts? What parts do we need? Matt Timion Electric and Solar powered 11 09-19-2005 09:37 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 11:52 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.