I have a 2003 Mazda Tribute that seems to have a bit of an idling issue. When my heat on my car is off, everything is fine as far as the idle speed. When I have the heat on, even when it is low, and I am stopped, the rpm’s rise a bit, then go back down to normal idling speed. The car also gives a little jump when I come to a stop. I think all of this is related to turning the heat on and off, as it doesn’t happen when the heat is on. Does anyone have any ideas?
Does it do it if you turn the temperature to cold and the fans/AC is on as well? If so, it isn’t really related to heat but may be related to some electrical load issue.
If it only does it with heat running, you may want to check the coolant level. It could be that when you turn the heat on, the level drops slightly to where the temperature of the car is not accurately measured by the computer so it hunts for an idle speed.
There are sensors related to that part of the system but I’d make sure you have a proper coolant level first before you get into anything else. It could just be a little low.
Thank you so much for your input! I don’t know if it does it when the A/C is on, but I can certainly check. Since you mention the coolant level, when I turn my car on in the morning, or after it has sat for a long time (all day) and it is cold out, my coolant light comes on, but as the car warms up it goes off. I can certainly check the coolant level and add as needed. Perhaps that is the solution.
Some cars will turn on the A/C system automatically when under certain conditions (like with the defrost selected, or windshield and floor are selected). If the A/C is kicking on (even if you leave it off), then those symptoms could very well appear. You may have to open the hood to see the A/C compressor turning on.
First step, though, is to check all your fluids, like RemcoW said.
Thank you! I’ll check the fluids first and then check the A/C compressor next if that doesn’t do the trick. Thanks so much for your help! :o)
So I added some coolant when I got home, and tested some of the different air controls. The idle increase occurs only when the A/C or defrost settings are on, which makes me think that it is the A/C compressor. When I just have straight heat turned on, it doesn’t occur. I have noticed too that when I turn on the heat (I usually always have it set to the windshield/floor combo) that it is a bit noisier. Thanks all for your help!
No, I don’t think anyone suggested it was your AC - just that turning the AC on loaded the engine differently. It puts a lot more strain on the engine than if you are just running heat. There’s are a couple of devices that are supposed to make up for that difference in loading.
One is called an Idle Air Control Valve and the other is called the Electric Load Detector. Ether one of those could be the issue.
IACV can be cleaned which sometimes solves the issue. Replacement usually isn’t particularly cheap. It is easy to get to most of the time but it tends to be an expensive part.
Edit: just googling the IACV for your make and model shows it is around $100 or so. Clearly that’s not too crazy so forget what I said about it being an expensive part.
I’m not suggesting you just start replacing parts or have parts replaced. Maybe bring it to a mechanic you trust and have him diagnose that problem independently.
I understand what you are saying now. Thank you! I do have a mechanic that I have taken it to in the past, so I’ll check in with him. Thanks so much!
No problem. Hope you’ll resolve your issue and it ends up being something simple and inexpensive.
One more question:
Does your AC seem to operate normally? When you turn it to cold, does it get properly cold?
Funny that you ask, I’ve noticed that it doesn’t get as cold as it used to. We don’t get super hot weather here in the Pacific NW, but I do use it in the summer, and this past summer I noticed it wasn’t very cold. Cold this be an issue?
There’s a chance it could be related.
If the AC doesn’t operate properly, it may not pose as large of a load onto the engine. When you turn the AC on, those devices make sure that the idle is adjusted to make up for that load difference. Since the load is much less than it should be, the idle would be higher than normal.
Usually the idle just stays higher than normal and does not come down but it could be that those devices mentioned before try to make adjustments to get the idle back to normal.
Of course, this is an educated guess at best because it is difficult to diagnose a car over the internet, not being able to look at things.
Maybe mention it to your mechanic. If the AC is at fault, it could be something as simple as the AC needing to be recharged.
I appreciate all of your “educated guesses”! It gives me something to talk to the mechanic about and at least give him the whole story and what I have tried or noticed.