tom24

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

hammeron

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.

tom24

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.

Nuke

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.

Simon1

Clean the throttle body.

tom24

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

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

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.

hammeron

agreed..... it's time to try the techron or seafoam

tom24

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?