2007 Hyundai Elantra 2.0L Stalls when hot outside, and A/C on...

Hello,
I'm reaching out because I'm stuck... My name is Vince, been a diesel mechanic for 15 years. I'm trying to help my brother in-law out with his car. It's a 2007 Hyundai Elantra 2.0L, with 213,132 miles. So the complaint is when he leaves work he drives 25 freeway miles home, as soon as he gets off at our exit, he comes to a stop and the car dies. So it usually happens when its hot, A/C on, in gear and only during the day (I know the problem isn't Photo Sensitive related .0)). I have tried driving evening and night and cannot duplicate the symptom which doesn't make sense. Today is about 103 degrees outside "Green Valley Az". Originally he thought it was spark plugs which I changed for him which I will include pictures. As you can see I thought the problem was plugs as well. I replaced the Idle air control valve Due to carbon build up and the gate inside was sticking... I have many days trouble shooting this car... I found the crank sensor with a hair line crack so installed a new one. Truth be told I thought that I fixed it until just a moment ago when I received a message saying the car died again. So fuel pressure is a 50 psi and holds strong. I have been using the torque pro app with a blutooth adapter, if that is wrong please tell me so... Any help or direction I would be so grateful for.... Thank you...

Could be as simple as the Idle Control Air Valve and/or throttlebody needs cleaned. I have seen this cause similar issues on smaller engined cars stalling at junctions as the AC, power steering and electric loads are relatively large compared to the engine power at idle.

+1 for throttle body cleaning

Okay, so I will include more pics. I have cleaned the throttle body with brush, rag, and cleaner, I cleaned the IAC port in the intake and installed a new IAC valve. Cleaned positive and negative battery terminals and cables. Checked fuel pressure. No codes whats so ever (I did check before I disconnected the battery, and after multiple test drives). I removed MAS (it is the grid style, not resistor style) and cleaned intake tube out (had some dust in it). I blew off MAS sensors and Temp sensor with a can of office compressed air. That upstream CAT looks in good shape, I took some pictures when I had the upstream o2 out. Like I said I'm using the torque pro app (I dont have a diagnostic scanner), a couple things that boggle me. ... First, it says the "Air Temp" is 68 degrees (when its like 85)but I dont think that will affect it. Second the Upstream o2 (o1s1) shows no data until the car is actually driven at road speed (it is a 5 wire sensor, I have never seen an o2 behave like this). I installed a new o2 sensor and it still behaved as such. Last thing is when the car does start Idling rough, I hear the all four injectors start clattering loudly. I thought it might be the fuel damper on the fuel rail but with the fuel gauge mesuring the fuel rail pressure it is a constant 50 Psi with no pulsation characteristics... Pictures are of old IAC, before the throttle body cleaning, a look at the upstream CAT. Truth be told the car Idles better with either the IAC unplugged or the MAS unpluged....

If temp sensor is reading wrong temp I would ohm test wiring and if no resistance replace sensor. Is that sensor the intake air temp sensor or ambient air temp sensor? If it is intake air temp this could be the issue causing stalling.

Also check powersteering pressure switch as with a full load on engine plus temps if switch goes wonky it won't send a signal to ecm to raise engine rpm to compensate for load on engine while turning. Might want to ask the owner of he was turning at an intersection when car stalled.

I will look it to what parameter the air temp is for, and will look in to the steering pressure switch. (I was unaware vehicles had a steering pressure switch that helps idle control). Do steering pressure switches log DTC's?

Code would appear if they are out of range. I.E. shorted to voltage, shorted to ground, circuit open. below are the codes that would set you can look them up on Google as my phone won't let me copy and paste with a cracked screen
P0550, p0551, p0552, p0553

Okay thank you for the codes. I will ohm the pressure switch under load, and no-load just in case. I will be getting the car again to troubleshoot more. I just heard from him, I again asked if by chance he was turning his wheels when stopped. His words, quote "No, it always happens when I'm at a stop light or stop sign." I did try searching for a vacuum leak with water previously, none found. Also while engine running disconnected MAS and pulled intake tube off and incrementally plugged Idle port in throttle body to see if I could locate or amplify a vacuum leak.... Nothing found. So the only other thing I can possible think of is pull the PCM schematic and see what all inputs there are that may be part of increasing the IDLE? I see there is an input for when the A/C is on. Other than that I don't know. I have had some good challenges over the years, but I have to admit this is the most difficult one I ever had to diagnose. I do appreciate all your help, Thank you. If I am becoming a nuisance let me know and I can quit posting. Thanks

Maybe the problem isn't the engine. It sounds like this is happening right after air stops flowing across the AC condenser coil. Could be a cooling fan problem or something increasing AC compressor load to the point where the IAC can't keep the engine running.