Horrible Mileage......Keep getting check gas cap message.... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


2000-2005 Discuss your 2000-2005 Bonneville SE, SLE, and SSEi Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 04-28-2008, 09:13 AM   #1
Senior Member
Posts like a 4 Banger
Thread Starter
 
Join Date: Feb 2008
Location: indiana
Posts: 110
Thanks: 0
Thanked 0 Times in 0 Posts
Spl170s is on a distinguished road
Default Horrible Mileage......Keep getting check gas cap message....

On my 2000 SLE.....its got 78K on the clock.

I only got 350 miles to my last tank in the car... i drive 40 miles each way to work.....90% of that drive is 60-65 highway speed. I don't drive the car hard at all....

I have put a brand new gas cap on it from stealership.

Here are a few probably stupid questions....
1. When you remove the gas cap and put the gas pump filler in, you see a metal flap of sorts that is spring loaded at the filler neck. i noticed mine does not fully close for whatever reason..staying open some. is this a problem?

2. When i stopped at a light over the weekend, i noticed a gas smell and happened to look out my side view mirror....and i saw what looked like gas fumes coming from the gas cover area........

All i know is that the new cap is definetely on all the way...always make sure i click it many times when putting back on. Also, i have cleaned the metal on the filler neck to make sure of good seal.

I picked up new TR55 plugs for the car, but, hadn't bought the wires yet. Was going to start there on the tune up.

Any ideas on the gas smell/cap issue? Always the same P0440 code.
Spl170s is offline   Reply With Quote
Old 04-28-2008, 10:53 AM   #2
Senior Member
True Car Nut
 
Join Date: Jul 2004
Location: Grand Rapids, Mi
Posts: 5,656
Thanks: 0
Thanked 0 Times in 0 Posts
Archon is on a distinguished road
Default

There are many things that can cause the P0440 code. Once common issue is the vent valve near the rear tire. Taking it apart, cleaning and lubing, and reinstalling often solves the problem. Other areas to check are the filler neck, the evap cannister under the car, the solenoid under the hood, as well as all of the tubes, and connections for each.
Archon is offline   Reply With Quote
Old 04-28-2008, 11:26 AM   #3
Senior Member
Posts like a 4 Banger
Thread Starter
 
Join Date: Feb 2008
Location: indiana
Posts: 110
Thanks: 0
Thanked 0 Times in 0 Posts
Spl170s is on a distinguished road
Default

thoughts on the metal flap on the filler neck not closing all the way? this be a problem?
Spl170s is offline   Reply With Quote
Old 04-28-2008, 11:35 AM   #4
Senior Member
True Car Nut
 
Join Date: Jul 2004
Location: Grand Rapids, Mi
Posts: 5,656
Thanks: 0
Thanked 0 Times in 0 Posts
Archon is on a distinguished road
Default

I believe the gas cap will seal that area pretty well, so I don't think it is a problem. I can't give you a 100% on that, though.
Archon is offline   Reply With Quote
Old 04-28-2008, 11:56 AM   #5
Senior Member
True Car Nut
 
Join Date: Oct 2005
Location: Central Florida
Posts: 7,030
Thanks: 0
Thanked 0 Times in 0 Posts
lash is on a distinguished road
Default

Follow Archon'* advice and check those items he mentioned. One of them is likely to be the culprit.

If you check each one of those items and the problem persists, then you should also do a careful and thorough check of all your vacuum lines, hoses and connections. Small cracks in your rubber connectors or lines can and will produce the P0440 code too.

It is most likely that the fix for this will be very inexpensive, just tiresome to trace down.
lash is offline   Reply With Quote
Old 04-29-2008, 02:37 PM   #6
Senior Member
Posts like a 4 Banger
Thread Starter
 
Join Date: Feb 2008
Location: indiana
Posts: 110
Thanks: 0
Thanked 0 Times in 0 Posts
Spl170s is on a distinguished road
Default

question....can the vent solenoid issues cause bad MPG on the car?

I ordered my beldon wires today. got my Tr55s also...will put that all on this weekend...as well as basic tune up items. Starting to wonder if its time for a new O2 as well.
Spl170s is offline   Reply With Quote
Old 04-29-2008, 08:03 PM   #7
Mark Fahey
Guest
 
Posts: n/a
Default

I would make sure the engine is coming up to full operating temperature and that your are in 4th gear with the torque converter locked up at highway speed. Also check your tire pressures.
It'* possible that your O2 sensor needs replacing but if this is a sudden problem, I'd look elsewhere first.
  Reply With Quote
Old 04-29-2008, 08:13 PM   #8
Senior Member
Posts like a 4 Banger
Thread Starter
 
Join Date: Feb 2008
Location: indiana
Posts: 110
Thanks: 0
Thanked 0 Times in 0 Posts
Spl170s is on a distinguished road
Default

i can't say that it is a sudden issue really. have only owned car maybe 2 months now..and hadn't checked or watched mileage till now.

i am working with the solenoid or vent back by the rear tire tonight...

only thing i am seeing is the rubber lines that tee and whatnot on the assembly were dry rotted looking and crumbling. so i replaced those...not sure what else i can actually do on that assembly though.
Spl170s is offline   Reply With Quote
Old 04-29-2008, 10:13 PM   #9
Senior Member
True Car Nut
 
Join Date: Jul 2004
Location: Grand Rapids, Mi
Posts: 5,656
Thanks: 0
Thanked 0 Times in 0 Posts
Archon is on a distinguished road
Default

If the lines were crumbling, that could very well be the problem that is setting the code. The vent valve comes apart by un-clipping the plastic tabs that hold it together. Clean it up, lube it with either silicone, or white lithium grease, and reassemble. A problem in your evap system will not be the cause of poor gas mileage.
Archon is offline   Reply With Quote
Old 04-30-2008, 01:12 AM   #10
Senior Member
Posts like a Supercharger
 
Join Date: Jun 2006
Location: Moon of meepsorp
Posts: 183
Thanks: 0
Thanked 0 Times in 0 Posts
Roadrunner is on a distinguished road
Default

Quote:
Originally Posted by Spl170s
thoughts on the metal flap on the filler neck not closing all the way? this be a problem?
Whenever I see that, my first thought is that someone tried to siphon gas.
Roadrunner is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
"Gas Cap Loose Check Cap" - 2001 Buick Lesabre eb-86 Buick 9 04-08-2015 01:31 PM
2000 silverado Z71 horrible gas mileage Owen2010 General GM Chat 20 02-16-2012 08:25 PM
Check Gas Cap message... Pologuy 2000-2005 13 01-15-2010 07:11 PM
1992 SE bonnie getting horrible gas mileage tbosu1998 1992-1999 6 10-21-2009 09:11 PM
Gas Cap message - AGAIN!!! Jayman 2000-2005 31 05-20-2007 12:49 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -4. The time now is 10:58 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.