[JAY'SRED02]

Yesterday my wife drove our car to town and used the air conditioning for the first time. When she returned she was complaining about how the car ran she said it was constantly surging or jerking. I drove it down the road and noticed the same thing but only when the air is on . She even felt it doing it while in the passenger seat while I was driving. Please guys tell me this ain't normal!

[White99stang]

no its not normal, something in the a/c is taking lots of power or voltage from your motor.

[mdvaldosta]

First thing that comes to mind is a bad clutch / compressor. I'd check the IAC for buildup too just for a shot in the dark. Other things can cause this issue too, like the TPS and I'm sure I'm missing others. I'd go for cleaning the IAC first as that won't cost anything.

[JAY'SRED02]

I didn't think it should have that much effect on the engine and the way it feels at normal cruising speeds. Do you clean the IAC with contact cleaner just like cleaning the MAF?

[Screemin3o2]

If it runs fine without the a/c on then it doesn't have anything to do with the IAC. IAC just allows a small amount of air to pass through while the throttle plate is closed so the engine can run. That's wierd for it to do that. I will ask at school on monday to find out what would cause that exactly.

[mdvaldosta]

The IAC also bumps the idle when the AC is on...

[Screemin3o2]

Oh it does, I didn't think it was the IAC that controlled that.

[Twist 2 Go]

what you are probably feeling is the ac clutch cycling on & off which is somewhat normal. You can usually here a dull click when this happens also. They usually cycle every 15-30 seconds depending on the ambient temp. If it's happening more than this, could be a defective pressure cycling switch or a low freon charge. How does the ac cool?

[JAY'SRED02]

Ok Guys drove the car last night to Nashville and noticed the same surge at cruising speeds with the air off but it is very minor and not as noticeable as with the air on . The air blows very cold and the compressor cycling makes sense but I can't imagine it being this noticableable. I will check the IAC since its doing it with the air off just not as bad. Thanks for the replies !

[Twist 2 Go]

you will not feel the iac while driving down the road. only at stops.

[JAY'SRED02]

I carried my car to the dealer last week for what I thought was an air conditioner problem causing the occasional miss when the air was on. The dealership called me and said they couldn't find any problems but wanted me to drive the car and show the tech what it was doing . I did that and he said what I was feeling felt more like a miss fire to him but didn't have any suggestions cause it wasn't throwing any codes . Should I start with plugs or is there anything else I should look at first? What would a faulty MAF sensor cause because the tech first said that the oil from the K&N filter "may" have caused this problem but my warranty wouldn't cover that . That was the first thing I cleaned when I first noticed the problem so I know its not dirty but it may be bad . I just want to solve this problem and I know you guys got some suggestions. Thanks

[Drgnracin72]

cheack plugs, wires, all that little crap before you start tearin into the big stuff

[99mustang232]

that is typical when they are unable to determine the problem the blame goes on aftermarket parts, could always take it to another dealer...

[AtlanticBlue99]

I had a similar problem. I would turn the AC on and the car would slug a little- It would drive fine, cut out, come back to fine (in a matter of seconds)... and it did actually die out on my twice, but started right back up. This happened off and on for 2 weeks before the battery and alternator died at the same time. I am sure one led to another, but everything else seemed fine, and I still had power with the AC off. I even checked volts on the battery and checked charging amps on the alternator. Everything checked out okay, but that ultimately was my problem. Just a suggestion.

[JAY'SRED02]

Took the car by advance auto today to check the electrical system out . The battery is fine but the alt is putting out 13.5 volts at idle and with the air and lights on it drops to around 13volts . The guy there said at idle the alt should be putting out 14.25 volts and that my alt was probaly going out and would probaly take my battery at the same time. Is this guy correct about the volts and could this be my culprit to my air conditioner problem . This seems to be identical to AtlanticBlue's problem. I am leaving next week to cruise the winding Blue Ridge Parkway and I definitely don't need to break down.

[AtlanticBlue99]

I wouldnt trust those guys. I took my car to Autozone to test my battery and Alternator voltage/amperage, and both checked out okay but ended up having a bad alt and 2 dead battery cells.

With that said, get a new alt at least, maybe a battery for good measure depending on how long you've had the current battery

[james117]

I had the same problem with either the heater on and the ac on and found out it was a little $30 part I bought on ebay it is a sensor attached to your EGR valve called the DPFE sensor once changed it will stop the surging and rev problem I would be at a light and the car would go from 500 rpm to 750 or higher when driving it would jump min 250 rpm and all mechanics said it was fine but it is a pain when you have your vehicle surge. so I went through the painful act of replacing the EGR, TPS, IAC, cleaned out the full fuel system changed the spark plugs and injectors all reccomended by mechanics to have the same problem then I did some reading on the internet and found that this little sensor could be the problem if not preforming properly, so I said why not and I also changed the tubes for it a few bucks later and the car ran like it was brand new and now it is 2 years later and is running smooth no surge or anything else but I learned my lesson here is a link of what the part looks like http://www.teamfocus.us/dpfeservice.htm but it is the only one that is clear but for ford focus same for every for