Search



Go Back   MustangForums.com > Ford Mustang Tech > 2005 - 2014 Mustangs > GT S197 General Discussion > 4.6L V8 Technical Discussions
Sign in using an external account
Register Forgot Password?
Search

4.6L V8 Technical Discussions Any questions about engine, transmission, or gearing can be asked here!

Welcome to Mustang Forums!
Welcome to Mustang Forums.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!


Reply
 
 
 
 
Thread Tools Search this Thread
Old 05-23-2013, 10:07 PM   #1
Ricardo
3rd Gear Member

 
Ricardo's Avatar
 
Join Date: Oct 2009
Vehicle: '07 Mustang GT
Location: Utah
Posts: 718
Default '07 GT Misfire Help!

So over the past week my GT has developed a slight lope and a definite misfire at idle, part throttle, and cruise, also in between easy shifts it will misfire when dropping RPMs . But there is absolutely no loss of power and the misfire disappears at full throttle. It pulls hard with no hesitation at WOT.
Did a few searches here and found a few posts explaining this is common with o2 sensors going bad. Took it to the dealership and they found a few misfires but said o2 sensors are working perfectly. They changed my fuel filter and said the misfire didn't return. It came back after a few miles!
Cleaned throttle body, sprayed the MAF with MAF cleaner, checked for any vacuum leaks.
Ran Scantool software and STFT is within normal operating range and o2 voltage seems to be too.
But then I see the o2 sensor on one side do this during a misfire for a fraction of a second. The other side doesn't drop off like this and this only happens during a misfire.


Now it's down to COP, spark plugs (4k on current OEM replacement set-followed TSB to the letter), and o2 sensors.
Is this enough information to make an educated guess on my next step or do I need more data? I can screenshot any data needed. Forgive me for being such a n00b to this kind of problem, I've trying hard to research all I can. And thanks for any help, it's frustrating when a dealership says they fixed an issue and it reappears.


EDIT: Just to be absolutely sure, I ran SCT, Scantool, and Torque for any codes and all of them detected no codes this entire time.
This ad is not displayed to registered or logged-in members.
Register your free account today and become a member on Mustang Forums!

Last edited by Ricardo; 05-23-2013 at 10:13 PM.
Ricardo is offline   Reply With Quote
Old 05-24-2013, 08:37 AM   #2
jpplaw
2nd Gear Member
 
jpplaw's Avatar
 
Join Date: Jun 2010
Vehicle: 2009 Ford Mustang GT
Location: RI
Posts: 492
Default

Plugs usually go bad under load.
COP's usually go bad under load.
Fueling issues are usually under load.
However, your problem is just the opposite of the above.
If it disappears at WOT, then it is a closed loop problem. Try changing out that O2 and use the Motorcraft brand only.
__________________
2009 GT Coupe - Daily Driver
Brenspeed B326
FRPP Stage 1 ported heads
E-Force /2.75” Pulley - IW 18% OD Balancer
ID 725 Injectors
Comp Cams 127450's
GT500 Dual Fuel Pumps w/ dual VMP boosters
Fluidyne Aluminum Radiator
AFCO Heat Exchanger w/ fans
Dad's Intercooler tank
Kooks 1 5/8” Headers, Green Cats, H-pipe
PI 3200 rpm Converter
3.73 Gears
Dynotech Aluminum Driveshaft
Strange Adj. Struts and Shocks
GT500 Brembo Brakes & BAER 14” Rotors

DYNOJET: 633 rwhp/623 rwtq (4/2/14)

jpplaw is offline   Reply With Quote
Old 05-24-2013, 08:54 AM   #3
dlazrael
5th Gear Member

 
dlazrael's Avatar
 
Join Date: May 2005
Vehicle: 08 Ford Mustang GT
Location: Maryland
Posts: 2,003
DLAzrael43 DLAzrael
Send a message via AIM to dlazrael Send a message via Yahoo to dlazrael
Default

My situation wasn't quite like yours, but what ended up happening is I had some water get down past the COP boot and got to the top of the spark, the end result was the spring piece inside the boot corroded and caused me the problem, I replaced that part ($7 at autozone) and worked like a champ - so you MIGHT want to check the boots/connectors before running off spending over $200.... Though with the data you have it does sound more like an O2 sensor
__________________
-George
Firefighter/Paramedic, Naval District Washington, NSA Bethesda Station 50
Firefighter/Paramedic, Morningside Volunteer Heavy Rescue Co 27 (PGFD)
Paramedic, Calvert Advanced Life Support

Cpl, USMC (Ret.)

2008 Ford Mustang GT: Whipple Charged, Pypes Violators, SCT Tune, Steeda TriAx, ProChamber, Sequentials, OEM 19" 2011 GT/CS Charcoal Wheels, Exedy Mach 500 Clutch w/ LW Flywheel,Steeda S/S-Springs, LCA and UCA
dlazrael is offline   Reply With Quote
Old 05-24-2013, 12:18 PM   #4
Mr.Ski
2nd Gear Member
 
Join Date: Aug 2009
Vehicle: 2009 Ford Mustang GT
Location: Somewhere in southern Indiana
Posts: 166
Default

An exhaust leak will cause a misfire like this too.
Mr.Ski is offline   Reply With Quote
Old 05-24-2013, 02:20 PM   #5
Ricardo
3rd Gear Member

 
Ricardo's Avatar
 
Join Date: Oct 2009
Vehicle: '07 Mustang GT
Location: Utah
Posts: 718
Default

thanks guys! Im changing my front o2 sensors right now, the rears were turned off in the tune anyways.


I do have an exhaust leak from the manifold to midpipe that just will not go away. been there since day one but I'll throw some copper gasket maker on it and report back.
Ricardo is offline   Reply With Quote
Old 05-24-2013, 03:00 PM   #6
Ricardo
3rd Gear Member

 
Ricardo's Avatar
 
Join Date: Oct 2009
Vehicle: '07 Mustang GT
Location: Utah
Posts: 718
Default

and by 'change' I meant find out a manual transmission holds heat a lot more efficiently than a 4.6dohc engine can and that getting that DS one makes one curse life as a man with big hands and forearms
Ricardo is offline   Reply With Quote
Old 05-24-2013, 11:42 PM   #7
Ricardo
3rd Gear Member

 
Ricardo's Avatar
 
Join Date: Oct 2009
Vehicle: '07 Mustang GT
Location: Utah
Posts: 718
Default

o2 sensor change did nothing...moving on to the plugs, if that doesn't work then it has to be the coils. I cant believe a DEALERSHIP could't find the cause with all their fancy computer diagnostics and knowledge.
Ricardo is offline   Reply With Quote
Old 05-25-2013, 01:47 AM   #8
drewsky
3rd Gear Member
 
Join Date: Oct 2004
Vehicle: 06 GT Legend Lime and 1967 CP
Location: Arizona
Posts: 736
Default

Try the exhaust leak problem .. Hopefully will solve it !
drewsky is offline   Reply With Quote
Old 05-25-2013, 04:53 PM   #9
moosestang
6th Gear Member
 
Join Date: Sep 2006
Vehicle: 2006 mustang gt
Location: Gainesville, FL
Posts: 11,246
Default

It doesn't have to be the plugs or coils, it could be a compression problem.
__________________
Boost or Buell, decisions, decisions.

whipple HO SC,FRPP k springs, Pypes mid mufflers, hurst, frpp TB, 4.10's, spohn lca's, adj. UCA, relo brackets, 1 piece DS, spec stg 3+ clutch. 12.52@117.6mph so far with a 2.01 60 ft time

Pumpkin jacking addict
moosestang is offline   Reply With Quote
Old 05-25-2013, 09:32 PM   #10
Ricardo
3rd Gear Member

 
Ricardo's Avatar
 
Join Date: Oct 2009
Vehicle: '07 Mustang GT
Location: Utah
Posts: 718
Default

Quote:
Originally Posted by moosestang View Post
It doesn't have to be the plugs or coils, it could be a compression problem.


this is good to know as a possible issue. This is a great lesson in how complex our engines really are! Wish I could just soak up all you guys's knowledge about our cars.


edit: if it means anything, my car has been babied its entire life with just one recent dyno run and three stoplight encounters. no racing or beating on it.

Last edited by Ricardo; 05-25-2013 at 09:36 PM.
Ricardo is offline   Reply With Quote
Old 05-25-2013, 09:32 PM
MustangForums
Ford Mustang




Paid Advertisement

 
 
 
Reply

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

Forum Jump

Advertising

Featured Sponsors
Vendor Directory
New Sponsors
All times are GMT -5. The time now is 06:38 AM.

© Internet Brands, Inc.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.5.2

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company
Emails Backup