Why does my 2003 Dodge Grand Caravan idle smooth in drive with A/C on, but not with A/C off?

20

Asked by May 06, 2017 at 11:34 PM about the Dodge Grand Caravan

Question type: Maintenance & Repair

My 2003 Dodge Grand Caravan idle smooth in drive with A/C on, but not with A/C off.  I have 296,000 miles on it.  At a stop light, the RPM goes from 700 to below 600 in drive.  When it gets near 600, it starts to idle rough.  If I hold the break and just tap the accelerator lightly, it will start idling smoothly again at around 700 RPM.  I have spent many hours and months trying to trouble shoot this problem; are there any suggestions?

7 Answers

250

When you turn on the AC the compressor rise the engine rpm.but when you turn off the vehicle will stall because need tuneup and use clean injectors you will see some different.

6,735

scan for codes even if the light ain't on

20

All of that has been done.

1 people found this helpful.
20

Engine does not stall; it only run rough when the RPM lower to 600 RPM and lower in drive. There are no codes. Tuneup was recently done and bad injectors replaced and then cleaned. Here is another part of the puzzle. Engine idle smooth in reverse, neutral and park.

6,735

intake leak ? get starting fluid around gaskets and see if idle changes , check for worn/cracked hoses and vacuum lines

20

I was thinking the same thing; I tried carburetor cleaner, brake cleaner around all area I could reach with the engine running. No change in RPM. I think I can hear a leak when I accelerate hard up to 80. I will check under van soon for vacuum leak, but is too afraid to have the engine running at the same time. I don't have a smoke machine.

1 people found this helpful.
6,735

take the tension off the serp. belt and see if the A/C pulley turns freely engine off .

7 people found this helpful.

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