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!


2008 Mustang GT / Hesitation, rough idle on warm weather

Reply
 
 
 
 
Thread Tools Search this Thread
Old 11-10-2011, 12:11 PM   #1
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default 2008 Mustang GT / Hesitation, rough idle on warm weather

Hi everyone,

I'm a relatively new Mustang- owner. I bought the car, 2008 Mustang GT manual transmission, in May 2011 with ~25000 miles on it. The car is fully stock as far as I know. I live in Texas, this might be an important part, you'll see if you read on

Symptoms:
So, from the very beginning I've had some problems with the car hesitating when I'm taking off normally. It feels like it wants to choke and there's no torque on the low revs, so I need to really let the clutch slip more than I'd like to (I've been driving manuals for over 15 years).
Also, the idle has been a little rough, and, when idling, if I quickly give it some revs and lay off, the revs will first go up and then down to around 500rpm for a few seconds before rising back up to around 800rpm where the idle seems to settle. Also doing this will cause some exhaust popping.

All this just makes the car very difficult to drive "smoothly". But the car seems to give me full power once I get it moving and stomp on the gas pedal.

History and story:
I took the car to the dealer in June due to these issues, but they did not find anything. And there aren't any, and never have been, CEL -lights or anything indicating any problem. So I figured that the car is just difficult to drive.

But now, it seems that the winter has finally arrived in Texas and the temperatures have plummeted. And my car is driving like a dream! Looks like
the colder the weather, the better it works. So, I took the car to the dealer this morning, explained everything, and they said that there's basically no chance they're going to find anything wrong from the car if it's not acting up and there are no warning lights going off! Mind you, they didn't find anything in the first place even though the car was acting up They just asked me to return when the car is acting up again.

So, I would really appreciate any ideas on what to check or try out.
I still have a month of factory warranty left on the car, so I'm kinda itching to get it fixed asap. But it looks like I need to gather some evidence before going back to the dealer. I'm not very experienced on fixing/troubleshooting cars, so also if you have any "how to's" they would be of great help.

Thanks!
Tom
This ad is not displayed to registered or logged-in members.
Register your free account today and become a member on Mustang Forums!
tom24 is offline   Reply With Quote
Old 11-10-2011, 03:00 PM   #2
hammeron
6th Gear Member
 
hammeron's Avatar
 
Join Date: May 2006
Vehicle: 2006 GT
Location: Nicely done
Posts: 11,738
Default

if you live in a county that requires emissions testing, i would
take it in to make sure it can pass. the exhaust popping doesn't
sound normal to me for a completely stock vehicle.

the tests are free in my county, for people just wanting to make
sure everything is running right.
hammeron is offline   Reply With Quote
Old 11-10-2011, 05:03 PM   #3
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Thanks Hammeron, that's a good idea.
I think I'll wait for a warm day and if the car is acting up that day I'll do what you suggested. Again, driving back from work everything was great, it's around 65 F right now..
But then again, I'm not sure if my theory is accurate I guess this all could be just a coincidence with the ambient temperature. The engine temperature does not seem to affect how it's behaving.
tom24 is offline   Reply With Quote
Old 11-10-2011, 07:19 PM   #4
Nuke
6th Gear Member
 
Nuke's Avatar
 
Join Date: Jun 2007
Vehicle: 2007 GT
Location: PA to KY ('07) to IL ('09) to MS ('10) to FL ('11)
Posts: 16,121
Send a message via AIM to Nuke Send a message via Yahoo to Nuke Send a message via Skype™ to Nuke
Default

The fluctuating idle is often a symptom of a dirty throttle body which is pretty easy to clean. I also like to run a good fuel system cleaner like Techron in the tank about every 8,000-10,000 miles. And if I suspect a problem, I'll run SeaFoam instead of the Techron. I'd also change brands of fuel.
__________________
Rick
07 GT Prem: Alloy, MT, 3.55's, Steeda CAI w/Brenspeed tunes, FRPP Stingers, 275/40/18 Goodyear Eagle F1 A/S on SVT Cobras (OE GT500's), 14" shorty, Wheelskin side scoops & qtr window louvers, A-H rear window louvers, SHR honeycomb blackout panel, Sequentials, Hella Optilux Extreme XY fogs, Silverstars
06 V6: Legend Lime, Pony Package, 14" shorty, Sequentials, Hella Optilux Extreme XY fogs, Silverstars
Nuke is online now   Reply With Quote
Old 11-12-2011, 12:48 AM   #5
Simon1
5th Gear Member
 
Join Date: Dec 2006
Vehicle: 2006 Mustang GT
Location: Redding, CA
Posts: 4,328
Default

Quote:
Originally Posted by Nuke View Post
The fluctuating idle is often a symptom of a dirty throttle body which is pretty easy to clean. I also like to run a good fuel system cleaner like Techron in the tank about every 8,000-10,000 miles. And if I suspect a problem, I'll run SeaFoam instead of the Techron. I'd also change brands of fuel.
Clean the throttle body.
__________________
[IMG][/IMG]

Motor Built by ST Motorsports
Tuned By Tony at Tuners Inc

11.05@129
Simon1 is offline   Reply With Quote
Old 11-12-2011, 06:41 PM   #6
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Thanks for all the replies.
Cleaned the throttle body today, and wow, it really made a difference. I have to say I was a little sceptical when I opened the throttle body and only saw a measly amount of dirt on it.

Just came back from a short test drive...
Almost all of the feeling of no torque on the lower RPM's disappeared, so I don't have to slip the clutch as much as before. Not sure if that cleaned out all the symptoms (the idle is still no completely smooth, although smoother, and the slight exhaust popping is still there), but if the car would drive like this from now on, I would be happy
tom24 is offline   Reply With Quote
Old 11-14-2011, 05:39 PM   #7
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Well, another warm day (looks like anything above 75F does the trick) and the hesitation is back, although it's not quite as strong as what it was before I cleaned the throttle body.

I took the car to the closest repair shop on the way from work and asked if they could check if the car passes the emission test, but they said they only have a OBD -reader and using that would require an error code. I'm starting to wonder if any of the repair shops / car dealers have any people anymore who can actually troubleshoot a car without a computer telling them what's wrong...

Could it be something like an O2 -sensor or MAF ? I had a look at the MAF and it seems to be quite easily accessible, would it be worth cleaning? I'm kind of hesitant since if I break it, looks like it's about 200$ to replace.

Am I wrong thinking it wouldn't be anything related to the fuel delivery system since it seems to be dependant on the ambient temperature??

Thanks again!
Tom
tom24 is offline   Reply With Quote
Old 11-15-2011, 03:30 PM   #8
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Drove into Napa Auto Parts last night and bought a can of MAF sensor cleaner and cleaned the MAF sensor.. Didn't notice any difference whatsoever. The car is like it was before, again acting jerky and sluggish today, but I guess it didn't hurt anyways...

I'm thinking the next thing to try would be to go get some fuel system cleaner and see if that does the trick.
tom24 is offline   Reply With Quote
Old 11-15-2011, 04:00 PM   #9
hammeron
6th Gear Member
 
hammeron's Avatar
 
Join Date: May 2006
Vehicle: 2006 GT
Location: Nicely done
Posts: 11,738
Default

Quote:
Originally Posted by Nuke View Post
I also like to run a good fuel system cleaner like Techron in the tank about every 8,000-10,000 miles. And if I suspect a problem, I'll run SeaFoam instead of the Techron. I'd also change brands of fuel.

Quote:
Originally Posted by tom24 View Post
I'm thinking the next thing to try would be to go get some fuel system cleaner and see if that does the trick.

agreed..... it's time to try the techron or seafoam
hammeron is offline   Reply With Quote
Old 11-15-2011, 06:23 PM   #10
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Quote:
Originally Posted by hammeron View Post
agreed..... it's time to try the techron or seafoam
OK, Seafoam is in the tank, I guess I just need to drive now..

I just still don't understand how the temperature could affect the behavior of the car if the fuel system is just dirty. Got any theories?
tom24 is offline   Reply With Quote
Old 11-15-2011, 08:21 PM   #11
SeVeReDiStOrTiOn
2nd Gear Member
 
SeVeReDiStOrTiOn's Avatar
 
Join Date: Feb 2006
Vehicle: 2005 GT
Location: CA
Posts: 441
Default

Quote:
Originally Posted by tom24 View Post
Thanks for all the replies.
Cleaned the throttle body today, and wow, it really made a difference. I have to say I was a little sceptical when I opened the throttle body and only saw a measly amount of dirt on it.

Just came back from a short test drive...
Almost all of the feeling of no torque on the lower RPM's disappeared, so I don't have to slip the clutch as much as before. Not sure if that cleaned out all the symptoms (the idle is still no completely smooth, although smoother, and the slight exhaust popping is still there), but if the car would drive like this from now on, I would be happy
When you cleaned it you removed the throttle body and then cleaned it right? That's the only way to get it really clean. It's just 4 bolts and undoing the wire harness...the gasket is reusable. I'd change the fuel filter also because it's probably the stocker.

Quote:
Originally Posted by tom24 View Post
OK, Seafoam is in the tank, I guess I just need to drive now..

I just still don't understand how the temperature could affect the behavior of the car if the fuel system is just dirty. Got any theories?
Have you noticed if the cooling fans are coming on? The temp gauge is just a dummy gauge that'll show an overheat condition right before going into limp mode. If you're getting to the borderline of that temp it would run like crap and might not show on the gauge. Also check radiator for any blockage from debris...like a bag or whatever. Your fuel pump could also be having issues with the heat lowering the psi when hot. But then again you'd probably have this issue across the rpm's. Keep at least 1/4 tank of fuel in the tank to help cool the pump just in case...so think of the 1/4 mark as E and refill when you get there.
__________________
SeVeReDiStOrTiOn is offline   Reply With Quote
Old 11-15-2011, 09:36 PM   #12
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Quote:
Originally Posted by SeVeReDiStOrTiOn View Post
When you cleaned it you removed the throttle body and then cleaned it right? That's the only way to get it really clean. It's just 4 bolts and undoing the wire harness...the gasket is reusable. I'd change the fuel filter also because it's probably the stocker.
Yes, I removed the throttle body alltogether. It was really easy to take off after I picked up an extension for my socket wrench The gasket seemed to be in good condition, didn't notice any hardening or anything on it. And yes, I recycled it.
Fuel filter.. hmm.. could do that. It just keeps adding up on the pile of things to change on my own expense, while the car is still under warranty. Just infuriates me that the dealer pretty much refused to do anything to the car until I get a CEL light lit up.

Quote:
Originally Posted by SeVeReDiStOrTiOn View Post
Have you noticed if the cooling fans are coming on? The temp gauge is just a dummy gauge that'll show an overheat condition right before going into limp mode. If you're getting to the borderline of that temp it would run like crap and might not show on the gauge. Also check radiator for any blockage from debris...like a bag or whatever. Your fuel pump could also be having issues with the heat lowering the psi when hot. But then again you'd probably have this issue across the rpm's. Keep at least 1/4 tank of fuel in the tank to help cool the pump just in case...so think of the 1/4 mark as E and refill when you get there.
Haven't really paid attention to the fans really .. because this issue is there from the very moment I start the car to the moment I turn the engine off. Well, actually, the hesitation is not there during the first 30 seconds or so when the engine is idling on higher revs and if I start driving during that time. (closed loop/open loop?! not sure )

So, engine warming up seems to have zero effect on the behavior, it stays the same whether the engine is cold or warm. For the issue to come up it looks like the ambient air temperature outside needs to be above ~74..76 degrees or so
tom24 is offline   Reply With Quote
Old 11-15-2011, 11:24 PM   #13
SeVeReDiStOrTiOn
2nd Gear Member
 
SeVeReDiStOrTiOn's Avatar
 
Join Date: Feb 2006
Vehicle: 2005 GT
Location: CA
Posts: 441
Default

Yea the fuel filter is under a maintenance item like the oil/air filter.

I mentioned engine and pump temps because I thought you were talking about 100*+ ambient temps which will raise both of those...but 75* won't make a difference.

Since you don't have a programmer you won't be able to data log the IAT and MAF. Do you know anyone with a 3v GT? If it was me i'd swap out the MAF (IAT sensor is built into it) with a known good one and see what happens. I'm thinking the IAT and/or MAF is giving bad readings as the air charge warms up and becomes less dense. The throttle position sensor could also be an issue and the ambient temp is just a coincidence.

The prob is we're starting to shotgun troubleshoot and the last thing you want to do is throw parts at it hoping for the best.
__________________
SeVeReDiStOrTiOn is offline   Reply With Quote
Old 11-17-2011, 12:03 PM   #14
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Quote:
Originally Posted by SeVeReDiStOrTiOn View Post
I'm thinking the IAT and/or MAF is giving bad readings as the air charge warms up and becomes less dense.
This was actually one of my main suspicions before, but I kinda discarded it after I cleaned the MAF/IAT. But I guess it could still be possible that the IAT is "working" so that it's not triggering a CEL -light, but only giving incorrect values..?

Quote:
Originally Posted by SeVeReDiStOrTiOn View Post
The throttle position sensor could also be an issue and the ambient temp is just a coincidence.
I guess it's possible, but if it's a coincidence, then I'm going to go buy some lottery tickets since I seem to hit it every time!

Quote:
Originally Posted by SeVeReDiStOrTiOn View Post
The prob is we're starting to shotgun troubleshoot and the last thing you want to do is throw parts at it hoping for the best.
Agreed.

Tom
tom24 is offline   Reply With Quote
Old 11-28-2011, 09:07 AM   #15
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Just wanted to update the thread.. no breakthroughs as of yet, but there's something else I have noticed.
The fuel efficiency has changed quite a lot; it used to be around 14-16mpg during the summer, but now it's averaging at 18.5mpg and my driving habits are the same. Actually I've been trying to "floor" it more to see if I can get back to 14-16mpg but it seems I cannot..

Tom
tom24 is offline   Reply With Quote
Old 12-12-2013, 01:49 PM   #16
srouxd162
 
Join Date: Feb 2011
Vehicle: 2002 Ford Mustang GT
Location: Louisiana
Posts: 3
Default

Quote:
Originally Posted by tom24 View Post
Just wanted to update the thread.. no breakthroughs as of yet, but there's something else I have noticed.
The fuel efficiency has changed quite a lot; it used to be around 14-16mpg during the summer, but now it's averaging at 18.5mpg and my driving habits are the same. Actually I've been trying to "floor" it more to see if I can get back to 14-16mpg but it seems I cannot..

Tom
Did you ever resolve this issue? I am having a similar problem and was wondering if you ever fixed yours.
srouxd162 is offline   Reply With Quote
Old 12-13-2013, 03:04 PM   #17
tom24
 
Join Date: Nov 2011
Vehicle: 2008 Ford Mustang GT
Location: Texas
Posts: 10
Default

Srouxd162:

No, never got it fixed.. still hesitating, seems to be a bit better the colder the outside temperature is, but it's always there. Still no Check Engine -lights or anything, after almost three years of driving with it.

I took the car to an independent service shop and they did tests to the car for two days and came up with nothing, hooked it up to computers etc.. No misfires in cylinders or anything else wrong according to them. Ford can't find anything wrong with it either.

I've changed the MAF and my mileage went up a bit but didn't resolve the issue.

One thing that I've been thinking is, perhaps the previous owned put a tune on the car and then when he sold it off just returned it to OEM -parts but did not return to the original tune..?

If you resolve yours, I'd be extremely grateful for any tips.. I've just dealt with it so far, but it's extremely annoying and embarrassing issue.. I'm embarrassed to let anyone else drive the car, they stall it immediately when they try to get going and the first comment I hear is "oh, funny how it seems to stall so easily"

-Tom
tom24 is offline   Reply With Quote
Old 12-13-2013, 03:38 PM   #18
waykooljr
3rd Gear Member
 
waykooljr's Avatar
 
Join Date: Jun 2006
Vehicle: 2006 Mustang GT
Location: Texas
Posts: 553
Default

Seems like you'd get some sort of code if it wasn't running the stock tune without parts that went with the tune. It's possible to to have the computer flashed back to stock but there will probably be a cost involved. I had to do this for mine because I had to have a tuner repaired and my stock tune was lost. The dealership was charging $150.00 to flash it to stock but a local speed shop did it for the same price.

If you're sure it's stock, you might try hitting up the dealer you bought it from to see if they'll flash it to stock for you, it's the least they could do if they sold the car that way.
__________________
waykooljr is offline   Reply With Quote
Old 01-09-2014, 10:15 AM   #19
srouxd162
 
Join Date: Feb 2011
Vehicle: 2002 Ford Mustang GT
Location: Louisiana
Posts: 3
Default

Quote:
Originally Posted by tom24 View Post
Srouxd162:

No, never got it fixed.. still hesitating, seems to be a bit better the colder the outside temperature is, but it's always there. Still no Check Engine -lights or anything, after almost three years of driving with it.

I took the car to an independent service shop and they did tests to the car for two days and came up with nothing, hooked it up to computers etc.. No misfires in cylinders or anything else wrong according to them. Ford can't find anything wrong with it either.

I've changed the MAF and my mileage went up a bit but didn't resolve the issue.

One thing that I've been thinking is, perhaps the previous owned put a tune on the car and then when he sold it off just returned it to OEM -parts but did not return to the original tune..?

If you resolve yours, I'd be extremely grateful for any tips.. I've just dealt with it so far, but it's extremely annoying and embarrassing issue.. I'm embarrassed to let anyone else drive the car, they stall it immediately when they try to get going and the first comment I hear is "oh, funny how it seems to stall so easily"

-Tom

Tom,

My problem is fixed and it was my original concern. My issue ended up being a vacuum leak upstream from the MAF sensor. On my 3.7, there is a crankcase breather tube that runs from the driver side valve cover to the the intake past the MAF. Inside the hose where it connects there are two O-rings designed to seal the tube to the nipple it fits on. Both of the O-rings were out of position allowing air to pass by. This air was unaccounted for by the ECU and throwing off my A/F ratio. Because the MAF wasn't able to meter the air, the ECU had no idea that the A/F ratio was off and therefore did not throw a CEL. Both O-rings were warped and one was cut, so I decided to replace them. Fortunately I found that they were very very close in size to paintball gun barrel O-rings and I have a drawer full of them, literally hundreds. I used them to replace the bad rings and reinstalled the breather tube being careful to ensure the O-rings got a good seal. Once it was all buttoned back up I cheld my breath and cranked her over. Low and behold the engine ran much better. Due to the car running rough for so long, it did take a couple of drives to completely smooth out and the ECU to correct some idle parameters. I can gladly say that my engine is back to how she ran before.

Hopefully this info helps you out. Check all of your vacuum hose connections and also any other connections associated with the intake, especially upstream from the MAF. Keep the thread updated with your progress.

-Wayde
srouxd162 is offline   Reply With Quote
Old 01-09-2014, 10:15 AM
MustangForums
Ford Mustang




Paid Advertisement

 
 
 
Reply

Tags
2008, 96, 98, adjust, chokes, good, gt, gts, hot, idle, idles, mustang, rough, warm, weather

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 01:47 AM.

© Internet Brands, Inc.


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