2007 Dodge Ram RPMs fluctuate while AC is on

Tiny
SKYWOLF
  • MEMBER
  • 2007 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 51,000 MILES
Yea I have a 2007 dodge ram hemi 5.7. It seems like that when I turn my ac on the rpms will go up and down about five ar six times within thirty seconds. It goes up and down a good 200 rpm. It seems also to be worse when my lights are on. I have asked alot of peaple and they are not sure. I have allready replaced the egr valve and cleaned the tube that goes into it. I also had the alternator and battery checked and cleaned the senser on the air intake. Please if you have any clues I would appreciate it. Im stuck. Lol. Thanks for your time.
Friday, August 6th, 2010 AT 7:30 PM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Has the check engine light come on? It sounds like a bad throttle position sensor or idle air control valve.

Let me know. Also, does it only do it with the AC on?
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Friday, August 6th, 2010 AT 11:32 PM
Tiny
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No engine light has come on. However it does it the most when I drive for about a half an hour and with the ac on. The only thing that is really does when the ac is off is that it would idle around 400 and then come back up to 600 when stopping at a light or stop sign. Somebody told that it could also be my compressor going out on the ac. So its still up in the air. Thanks for your reply.
James
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Sunday, August 8th, 2010 AT 7:12 AM
Tiny
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  • MECHANIC
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That is a low idle. My guess is the idle air control valve or throttle position sensor. Usually, if a compressor is locking up, they will make noise. Do you hear anything?
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Sunday, August 8th, 2010 AT 11:22 PM
Tiny
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The only noise that I hear is the compressor kicking on. When the compressor does kick on it bogs down the engine, and it kick on between 30 to 40 seconds at a time.
Today when I left from work (which is about 22 miles), I let the engine idle for about fifteen minutes too cool it off in the cab because I live in texas and it was hot. At any rate nothin happened. It idled at 600 rpms and did great, but as soon as I got in my town when (and only when) I stoped at the first light it started to purge up and down, and when I got to the house it almost stalled.
Some say yes to the idle air control sensor and yet some are saying it might be some kind of heat sensor that controls my choke. Also when and everytime I start the truck it takes a good ten minutes to idle itself down to 600. I restart it as soon as I shut it off and it takes the same amount of time. As far as without the ac it still goes down to about 400 then back up to six. Its wierd my friend has a 2006 ram hemi and his stays at 600 no matter what and it doesnt go down when he stops. Im sorry that this was so song, just frustrated. Thanks again for your help and reply.
James
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Monday, August 9th, 2010 AT 6:55 PM
Tiny
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  • MECHANIC
  • 110,176 POSTS
Honestly, it does sound like either the idle air control valve (IAC) or the throttle position sensor. As far as a choke, you don't have one. Via a temp sensor, the computer controls how rich or lean the fuel mixture is.

I would start with the IAC. Remove it and clean it to see if that takes care of the problem.

Let me know what you find.

Joe
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Tuesday, August 10th, 2010 AT 9:53 PM
Tiny
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Thanks for your reply. I will try that today. Have a good day.
James
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Wednesday, August 11th, 2010 AT 5:46 AM
Tiny
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James,

Let me know if it helps.

Joe
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Wednesday, August 11th, 2010 AT 9:05 PM
Tiny
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I tried that and it looks like the sensor is ok. I went ahead and took it to a mechanic that is close to my work and left it there, however about the second afternoon that he had it he called back saying that its not acting up. Well hes right. Its not no more except for maybe a slight miss. Well to make a long story short we (the mech, dealer and I), think it was that bully dog that was causing it. The dodge mech told me that those things are eating up the computers in the dodges for some reason, and he advised me to get a flash and then go buy the Edge Evolution performance chip instead of the bully dog that was in there.
So thats what im tryng today. Thanks for your time, and wish me luck.
James
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Saturday, August 14th, 2010 AT 6:05 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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That is most likely the problem. I do wish you luck, and let me know how it works out for you.

Joe
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Saturday, August 14th, 2010 AT 11:05 PM

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