Weird engine performance when running A/C.
Thread Starter
Joined: Mar 2010
Posts: 11
From: Fl.
Weird engine performance when running A/C.
This may be a bit long. Bear with me, because the problem started after a specific set of circumstances, and I don't what's related or isn't.
So I bought a new SUV, and decided to give my trusty ole 2006 GT a deserved breather. I drove the new car for 2 weeks, but didn't forget to turn on my 'Stang, to keep the battery from draining. I guess I didn't let it idle long enough, because the battery drained anyway. So I slow charged it with my charger, and started using the 'Stang gain on weekends. Prior to the 2 wk. break, the car was running normally. Not so afterwards. At first the engine ran rough, but eventually went back to normal, so long as the A/C was off. It's another story entirely with the A/C on. The higher the fan speed I run it on, the rougher it runs. RPMs fluctuate up and down, though not violently. Maybe 200-300 RPM. The car will often stall while idling or braking.
does anyone have any thoughts about what could be causing this?
So I bought a new SUV, and decided to give my trusty ole 2006 GT a deserved breather. I drove the new car for 2 weeks, but didn't forget to turn on my 'Stang, to keep the battery from draining. I guess I didn't let it idle long enough, because the battery drained anyway. So I slow charged it with my charger, and started using the 'Stang gain on weekends. Prior to the 2 wk. break, the car was running normally. Not so afterwards. At first the engine ran rough, but eventually went back to normal, so long as the A/C was off. It's another story entirely with the A/C on. The higher the fan speed I run it on, the rougher it runs. RPMs fluctuate up and down, though not violently. Maybe 200-300 RPM. The car will often stall while idling or braking.
does anyone have any thoughts about what could be causing this?
Gentleman's Relish
Joined: Feb 2005
Posts: 13,189
From: AZ
If the battery died, the PCM lost the 'learned' values for your idle and throttle trims.
https://support.bamaperformance.com/...6-Idle-Relearn
It should let the car relearn the fuel trims for idle. If that doesn't fix the problem then you might start looking at water in your fuel, dirty maf, and other culprits.
https://support.bamaperformance.com/...6-Idle-Relearn
It should let the car relearn the fuel trims for idle. If that doesn't fix the problem then you might start looking at water in your fuel, dirty maf, and other culprits.
4th Gear Member
Joined: Nov 2009
Posts: 1,826
From: SoCal
The higher fan speed (which equals increased load on the electrical system) correlating to idle quality and driveability I think says something.
I would verify that the battery and alternator are in good shape before getting worked up about anything else. Modern electronically (computer) controlled cars just simply will not run correctly when there are charging system deficiencies.
Your battery may seem ok, but honestly you should be able to park your car for two weeks without it going dead. Two months, two years, obviously that's a different story. But as long as the car is driven at least semi-regularly then two weeks parked shouldn't be an issue, IMO.
I would verify that the battery and alternator are in good shape before getting worked up about anything else. Modern electronically (computer) controlled cars just simply will not run correctly when there are charging system deficiencies.
Your battery may seem ok, but honestly you should be able to park your car for two weeks without it going dead. Two months, two years, obviously that's a different story. But as long as the car is driven at least semi-regularly then two weeks parked shouldn't be an issue, IMO.
Gentleman's Relish
Joined: Feb 2005
Posts: 13,189
From: AZ
The higher fan speed (which equals increased load on the electrical system) correlating to idle quality and driveability I think says something.
I would verify that the battery and alternator are in good shape before getting worked up about anything else. Modern electronically (computer) controlled cars just simply will not run correctly when there are charging system deficiencies.
Your battery may seem ok, but honestly you should be able to park your car for two weeks without it going dead. Two months, two years, obviously that's a different story. But as long as the car is driven at least semi-regularly then two weeks parked shouldn't be an issue, IMO.
I would verify that the battery and alternator are in good shape before getting worked up about anything else. Modern electronically (computer) controlled cars just simply will not run correctly when there are charging system deficiencies.
Your battery may seem ok, but honestly you should be able to park your car for two weeks without it going dead. Two months, two years, obviously that's a different story. But as long as the car is driven at least semi-regularly then two weeks parked shouldn't be an issue, IMO.
http://www.stangpit.com/wp-content/i...b/07-05-13.pdf
related but not related...
https://latemodel.cachefly.net/downl...sb12-07-04.pdf
Thread Starter
Joined: Mar 2010
Posts: 11
From: Fl.
If the battery died, the PCM lost the 'learned' values for your idle and throttle trims.
https://support.bamaperformance.com/...6-Idle-Relearn
It should let the car relearn the fuel trims for idle. If that doesn't fix the problem then you might start looking at water in your fuel, dirty maf, and other culprits.
https://support.bamaperformance.com/...6-Idle-Relearn
It should let the car relearn the fuel trims for idle. If that doesn't fix the problem then you might start looking at water in your fuel, dirty maf, and other culprits.
Since I've gotten knowledgeable responses from a few of you that know what they're talking about, let me add a bit to my initial post, and ask a new but related question: I knew about the computer having to readjust. I've experienced it before when I've had to disconnect the battery for any reason. In the past, though, it only took about 3-4 days of driving around for the computer to readjust. This time, although my 'Stang is getting driven 1 to 2 days a week, after about a month it was still running as badly as I described in my first post. The distance it was driven were about 8 to 32 miles per day.The battery and the alternator are relatively new. About a year, give or take a month. The car is a 2006. Did it fail to readjust because it was driven for just a few days a week, because the car has some years (And mileage! 176,000 miles.) or because of something I need to worry about or keep in mind?