Accordion hose behind the MAF.

 

I have checked the hose downstream of the MAF and there are no cracks or tears. The clamps are on tight.

A bit more detail:
The hunting happens when the fan blower is on or the A/C is on. Even if the fan speed is on low, the engine is running some accessory that is on the serpentine belt loop. I hear it click on and the the engine RPMs drop and then the engine surges in RPMs. When I turn off the blower fan then I do not have the issue. Any ideas?

 

I’m using my vehicle for work right now so I haven’t yet pulled AC fuse but I can confirm using heat that the RPM drops occur only when using an HVAC setting that involves defrost (blowing at windshield).

 

OK then get Forscan and a decent wired OBDII reader and see whats really going on.

 

How have you been checking for vacuum leaks? One of the best ways to do this is to use a spray bottle with water in it. Spray everything, including the intake manifold etc, since there may be a hairline crack in it that you can't readily see. The fact that the problem occurs when the a/c is on indicates to me that there might be an idle-up issue. This could be related to the a/c pressure switch activating erratically. This could be a result of either low or high refrigerant level. According to the workshop manual:

Idle-up speed (ATX: P, N position, MTX: Neutral position)

A/C on and refrigerant pressure switch (middle pressure) is off: 600-700 rpm​

A/C on and refrigerant pressure switch (middle pressure) is on: 750-850 rpm​

Electrical loads on: 650-750 rpm (MTX), 600-750 rpm (ATX)​

While turning steering wheel: 650-750 rpm​

I'm getting ready for work so when I get back home later I'll dig through the manual and se what else comes up.

 

Yessir. I checked for vacuum leaks with carb cleaner. Not the safest method, but it's what I had available.

I really like your theory on the A/C pressure switch. I am onboard with that diagnosis. It just makes sense. The AC compressor keeps kicking on and the issues I have are whenever the AC compressor runs. Is there a way to test the AC pressure switch, or is it just a matter of replacing and seeing if that has solved the issue. Is this a part I can source from Autozone, or is it worth to get an OEM from the dealer? Thanks.

 

I'm not necessarily saying that the refrigerant pressure sensor (as Mazda calls it) is faulty, though it could be. I'm wondering if the issue is with incorrect refrigerant levels. Either way, there are checks for both. Another possibility that I just thought about is the ambient temperature sensor being bad or perhaps disconnected.

Refrigerant Pressure Sensor:

Ambient Temperature Sensor:

What I think needs to happen, though is for the a/c system to be checked to make sure all is well. I have the specs of what the various parameters should be, and I'm willing to share them, but I'm not sure if an a/c shop is going to want to use the figures you bring in. Let me know if you need them.

 

I'm not necessarily saying that the refrigerant pressure sensor (as Mazda calls it) is faulty, though it could be. I'm wondering if the issue is with incorrect refrigerant levels. Either way, there are checks for both. Another possibility that I just thought about is the ambient temperature sensor being bad or perhaps disconnected.

Tango,

My apologies for the late reply. It's been bad weather here and I've been busy at work but today I was able to check into your recommendations:

I pulled the sensor connectors you recommended I check and everything was connected and connections looked okay.

My next plan of action is after Christmas having the refrigerant levels checked.

Thank you very much for your help!

 

The dealer really cleaned up pretending to repair this car.
The trouble shooting so far seems to have lead to the AC compressor. So two things seem at issue.
Low refrigerant causing the cycling or the Ambient temperature sensor causing it. This a ball park spec for the ambient temp sensor. 220-240 ohms at 70-80 degrees.
The AC system is designed to engage the compressor in defrost position to remove the humidity from the windshield area. Below 40 degrees OAT the compressor will not engage, instead heat would be directed to the windshield.
I know it's a mechanical magnetic clutch for the compressor but I don't remember hearing mine click, not from inside the car anyway. Perhaps the compressor clutch is the issue or even it's connector, causing the making and breaking it's engagement.

 

The dealer really cleaned up pretending to repair this car.
The trouble shooting so far seems to have lead to the AC compressor. So two things seem at issue.
Low refrigerant causing the cycling or the Ambient temperature sensor causing it. This a ball park spec for the ambient temp sensor. 220-240 ohms at 70-80 degrees.
The AC system is designed to engage the compressor in defrost position to remove the humidity from the windshield area. Below 40 degrees OAT the compressor will not engage, instead heat would be directed to the windshield.
I know it's a mechanical magnetic clutch for the compressor but I don't remember hearing mine click, not from inside the car anyway. Perhaps the compressor clutch is the issue or even it's connector, causing the making and breaking it's engagement.

Yeah, fairly disappointing. If I bring it back to the dealer I'm going to request they wave the diagnosis fee from last time since it didn't fix the original complaint.

Is the ambient temp sensor I checked also involved in the temperature display next to the odometer? The temperature displayed seems fairly accurate, but not sure if it gets its reading from a different sensor. Just curious.

Thank you!

 

Update: I brought the car to another mechanic and I explained the issue. He said the AC is acting normal and refrigerant levels are fine. He said the AC compressor should click on and off when its cold outside to prevent freezing of the refrigerant. What I don't get is why does the car do it even when its 80 degrees outside? He didn't have an answer. What is my next step?

 

Update: Took it to the dealership this time. They can't replicate the issue and said they can't find any vacuum leaks. I mentioned the potential of a cracked PCV hose and they said if it was a PCV hose the car would constantly be running poorly and it wouldn't be intermittent.

I'm frustrated and at a loss as to what is going on with my car. I'm almost ready to fire the parts cannon at the vehicle. Which part should I replace first?

 

Haven't been keeping up with this one - They said it wasn't the PCV but it's a $6 part and 15 minutes of your time to replace it (or something like $20 for the valve + reinforced hose) - if you haven't already it might be worth it.

 

The PCV valve and hose is behind the intake manifold on the 2nd gen. Not easy to get to.