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[Bourne]

Any ideas why my 3.0 MV6 idles perfectly when the climate control is on auto ,but as soon as i switch it off ,the idle speed falls to about 3-400 revs and only just keeps running.I cleaned out the icv thoroughly but it made no difference so I replaced it. Still no difference.All thoughts gratefully accepted.

[davlad22]

Is it just on startup or all the time?

[Bourne]

When it starts from cold it fast idles as it should , but once its warm(2-3 mins) its like it all the time.

[bigdods]

my old 2.5 used to do that. When you switch on the aircon the ECU bumps the revs up a bit as it takes power from the engine to run it. My old 2.5 used to drop to 400rpm with aircon off , made the car shake a bit. The 3.0 I have now doesnt drop so low, about 650 rpm aircon on , about 500 with it off. Just leave the aircon on ...

Im no expert but IIRC the idle cant be adjusted.... Im sure someone who knows what they are talking about will be along shortly to tell you whats wrong !

[mark.adams]

My old 1992 Carlton Diplomat used to do exactly that... very annoying

[hotel21]

I would think an air leak.  Try some carb cleaner sprayed around the breather covers (black ecotech bits) on the plenum and listen for increase etc in revs.....  If it does, air leak - replace o-rings etc as needed....

[TheBoy]

Remember, with A/C compressor off, the proper idle speed of v6 is 450rpm

[cem_devecioglu]

Here's my list
All the sensors (lambda, crank,cam,throttle, CTS,MAF)

plus ICV,gaskets,blocked EGR,de-CAT..All helped..

But very expensive list..

still not how I want..

better you show the car to the experts here..

[Bourne]

450 rpm seems somewhat low . Can it be reprogrammed?As its auto I like it to be a little faster.

[TheBoy]

450 rpm seems somewhat low . Can it be reprogrammed?As its auto I like it to be a little faster.

450 is fine with a/c off.  with a/c, should go to about 600.

There is a small amount of adjustment via tech2, but 450 is fine.

[cbowditch]

I have a 3.0 MV6 and was going to post the exact same question. Pressing the "Eco" button on the climate also has the same affect on the revs. In the winter I was planning to run with a/c off for a bit to save on fuel but the idle is too poor without a/c on, not worth spending a fortune replacing bits but it is annoying. Sounds like a design flaw to me.

[TheBoy]

I have a 3.0 MV6 and was going to post the exact same question. Pressing the "Eco" button on the climate also has the same affect on the revs. In the winter I was planning to run with a/c off for a bit to save on fuel but the idle is too poor without a/c on, not worth spending a fortune replacing bits but it is annoying. Sounds like a design flaw to me.

Why is it a design flaw? 6 cylinder engines can idle much lower than 4pots.  So the lower idle, which presents no problems, saves fuel and reduces emissions....

Remember, the A/C is the best dehumidifyer you can get in the winter when the car gets a little damp, and that the compressor needs to be run regularly to lubricate all the seals.

[cbowditch]

You are right about running the a/c on a regular basis to keep seals from drying up etc. I wasn't suggesting that I wouldn't use it at all, just less frequently in the winter.

450rpm is way too low. The car shakes and shudders when you are stuck in traffic for more than a couple of seconds and feels like it is about to stall. It hasn't actually stalled, but I didn't like all the shaking. At 600rpm with a/c on, the engine feels 10x smoother; like a V6 should really.

[Bourne]

How much is a "small amount of adjustment"? another 100 rpm might make all the difference.

[Mike Collins]

My recent running with A/C faulty reinforced my belief that it makes no noticeable difference to fuel consumption.