Rough idle

Juris · 2024-11-02T12:39:52Z

Hey guys, new member here.

My 09 IS250 has been rough on idle and I have read about carbon build up and also about other possible issues related with A/C and electrics. I am more inclined towards A/C and electrics because I read one of the post where the symptoms were exactly like mine ones. If I have A/C on and I stop in traffic lights engine drops down to 500rpm and feels like is about stall. My LED lights are flickering if A/C is on or I'm in reverse gear. Engine reacts even to seat adjustment which shouldn't be the case, right? So I thought it might be the Battery which I haven't changed since I bought the car and that's over 5 years ago now. So I went to Halfords the other day and they checked the Battery and said it seems to be fairly healthy one despite that I had some corrosion and buildup from acid around the terminals, which is a sign of needing a new Battery? But anyway I decided to clean the terminals and see if that changes anything. After reconnecting Battery I let the car run and switched on A/C and what seemed to be happening was that something was getting stuck/seized in A/C pulley and the rpms where jumping up and down. This had also happened some good while ago but it happened while I was driving and it stopped after that time so I didn't inspected any further at that time. But yeah, here I am with lots of questions but not many answers. What do you guys think? And should I take it to car electric for proper check?

Vintagesixtysix · 2024-11-02T13:25:30Z

I think your on the right track…

Looks like ac clutch is engaging and disengaging.

Did your ac work ok before this issue….

Is it fully gassed?

Does it work through the whole temp range?

Compressor issues are also not unknown.

Linas.P · 2024-11-02T13:58:27Z

Yes that sounds like stuck A/C compressor. I had that happen to me and basically A/C clutch tries to engage, nearly stalls the engine and disengages. There is next level to that - if the clutch also get's stuck, then it stalls the engine and you can't start it without removing the belt.

The fix - replace A/C compressor.

Juris · 2024-11-02T13:58:37Z

28 minutes ago, Vintagesixtysix said:

I think your on the right track…

Looks like ac clutch is engaging and disengaging.

Did your ac work ok before this issue….

Is it fully gassed?

Does it work through the whole temp range?

Compressor issues are also not unknown.

To be fair I haven't checked any of that as the A/C works just fine all the time, even when it was doing that, it was blowing air just fine. However just to be sure I will check again if it blows cold and hot air properly.

Juris · 2024-11-02T14:02:54Z

Just now, Linas.P said:

Yes that sounds like stuck A/C compressor. I had that happen to me and basically A/C clutch tries to engage, nearly stalls the engine and disengages. There is next level to that - if the clutch also get's stuck, then it stalls the engine and you can't start it without removing the belt.

The fix - replace A/C compressor.

Interesting. I assume it's not stuck entirely yet since one it's not doing this very often and two A/C seems to be working just fine. And do you think this is related with the other symptoms I described too?

Linas.P · 2024-11-02T14:11:21Z

How do you check if it is working when outside temperature is lower than lowest you can set on A/C?

In fact I once had this exact issue with Halfrauds - they re-gassed A/C and said it works fine, it was also November like now... I came back home, checked A/C and it does nothing. Came back and asked how did they test it, because it doesn't work... mechanic there came out with temp probe, stick it to the went, set the outside air, turn on the A/C and anounced confidently "look - it is blowing 7C"... then I pointed him out to the temperature read-out on the dash - it was 7C outside! Long story short - they refunded for A/C service.

Long story short - are you sure it is actually working, because if it is anything like my issue, then compressor does not turn at all. Also... I kind of doubt it works if A/C light is flashing, flashing light usually means there is problem with A/C system. Although you said "flickering", so maybe it is not the same thing.

What voltage do you get from alternator? Should be around 14V.

Juris · 2024-11-02T14:27:16Z

10 minutes ago, Linas.P said:

How do you check if it is working when outside temperature is lower than lowest you can set on A/C?

In fact I once had this exact issue with Halfrauds - they re-gassed A/C and said it works fine, it was also November like now... I came back home, checked A/C and it does nothing. Came back and asked how did they test it, because it doesn't work... mechanic there came out with temp probe, stick it to the went, set the outside air, turn on the A/C and anounced confidently "look - it is blowing 7C"... then I pointed him out to the temperature read-out on the dash - it was 7C outside! Long story short - they refunded for A/C service.

Long story short - are you sure it is actually working, because if it is anything like my issue, then compressor does not turn at all. Also... I kind of doubt it works if A/C light is flashing, flashing light usually means there is problem with A/C system. Although you said "flickering", so maybe it is not the same thing.

What voltage do you get from alternator? Should be around 14V.

That's a good point. But if the engine is hot shouldn't air be somewhat warm even if it's cold outside?

As for the lights flickering, it's not on the dash, it's my LED headlights. I don't have multimeter with me but I checked it some while ago and as far as I recall it was 13.6V

Linas.P · 2024-11-02T14:41:50Z

If you turn the heating on - then yes, otherwise it will be maybe couple of degrees warmer than outside air. So it is 4C outside and minimum temp on A/C is 16C... I am not really sure how do you know if A/C is working. The way to test it - you turn max heat and turn it on recirculation, it is nice if you have thermometer with you. So wait until it gets to say 24C, then turn A/C (still on recirculation) on and you should feel that air coming from vents is significantly colder. It think fully charged A/C blows ~13-14C on lowest temperature. But if temperature from vents is colder than that, then it is not coming from A/C.

13.6V is low, basically it is on the way out. I guess depends what is turned on in the car, but generally with engine running and just headlights you should be close to 14V. The alternator provides 14.4V, but obviously you needs some voltage to run the engine, so on perfectly working alternator you get like 14.1-14.2V. With loads of stuff turned on mine goes to maybe 13.95V, but generally stays just above 14V, which is healthy.

13.6V... is not totally failed, but it will charge Battery very slow, to have any meaningful charge on the Battery you need at least ~13.2V from alternator (fully charged Battery is 12.9V).

When you say LED lights, do you have aftermarket headlights? I thought you meant A/C LED?