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Ask Dodgerench Your Own Question
Dodgerench, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 3407
Experience:  30+ years Dodge/ Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I was having issues with the engine trying to stall out when

Customer Question

I was having issues with the engine trying to stall out when coming to stop or surging on idle when the air conditioner or heater would be running. Eventually, the engine started having misses and I noticed that the engine would make a high pitch moan when the engine was turned off. Then the ignition coil failed. I replaced the ignition coil, plugs and wires. This seem to fix the issue for a couple of months. It started happening again, so I got a new Ignition Coil again. The engine is still missing at random times and the high pitch moan is back. What could this be? Could it be a pressure build up issue or something else?
Submitted: 2 years ago.
Category: Chrysler
Expert:  AZTechBrian replied 2 years ago.

hello. Is the check engine light on and Does it moan every time you turn the engine off? Is there no moaning while it's running?

Customer: replied 2 years ago.
Currently, there is no check engine light on. It does not moan while the engine is running that is audible. It will only moan after the engine has been running for about 20 minutes and then turned off. I will try to make a video for you so that you can hear the sound that is occurring. Let me know if you need any other information. Thanks.
Expert:  AZTechBrian replied 2 years ago.

Ok. the engine wanting to stall when slowing down or running the air conditioner sounds a lot like an idle air control, IAC. I am curious if the noise your hearing is coming from the area of the throttle body, where the IAC is located. Did the whine sound come at the same time as the stalling and surging issue?

Customer: replied 2 years ago.
I tried to capture the sound with a couple of my devices but the audio had too much distortion. I don't hear the sound when the engine tries to stall. The closest example of the sound that I can think of when the engine is shut off is a low sound that tails off to a high sound like when I have hit a rubber ball very It's the only sound that I could relate it to. The sound seems to be originating from the area behind the ignition coil. Thanks.
Expert:  AZTechBrian replied 2 years ago.

The sound is coming from the driver side of the engine compartment? Not the passenger side?

Customer: replied 2 years ago.
Sounds like it is coming from somewhere behind the ignition coil.
Expert:  AZTechBrian replied 2 years ago.

which is located on the driver side of the engine compartment. All the accessories and everything else is located on the passenger side. Did the noise start at the same time as the engine stalling?

Customer: replied 2 years ago.
This sound started occurring at the same time I noticed the engine trying to stall. I noticed this initially as well before the first Ignition Coil and plug and wires were replaced. After the current new Ignition Coil was installed, the sound and the random stalling started occurring after only a few hours of engine time.
Expert:  AZTechBrian replied 2 years ago.

Ok. I'm not sure what the noise is but the stalling and surging when slowing down and also when turning on the air conditioning sounds very consistent with a bad idle air control. You would need a bidirectional scan tool to know for sure.

Customer: replied 2 years ago.
If it were a idle air control valve or TPS, would it occur all the time or can it be sporadic? It doesn't happen all the time but does happen more often after the engine has been running for longer periods of time. If I can get it hooked up to a computer, what would you be more interested in investigating?
Expert:  AZTechBrian replied 2 years ago.

If im sorry but I am going to have to opt out. All I have right now is my phone and I am volunteering at a hospital event. I don't want you to be left waiting on me. If you haven't been helped by the time i get back I'll be more than happy to help you further.

Expert:  Dodgerench replied 2 years ago.

Goood afternoon, this is Ed.

I must say that although I'm not sure where it'll end, I'm intrigued by your problem. If you don't mind, let me gather a little more info from you to be used by Brain or me and we'll see what happens.

My take on the moan sound is that it really is being made by a pressure differential of some sort, most likely vacuum decaying. Since idle control has much to do with air control, you might have some sort of air leak that is variable, confusing the everlovin crap out of the idle control system. I'm wondering if it might be a PCV valve that sticks in the high-flow position, creating at first an elevated idle from increased airflow, then causing a low pressure area to be built in the crankcase. The theory falls apart if your makeup air tube that leads from the front valve cover to the air cleaner is open and free, but it's a thought. You might want to check the air tube for being free-flowing all the way from the air cleaner into the crankcase by physically blowing through the air cleaner end of the tube. It should offer little resistance.

Likewise, you should feel a small amount of vacuum on this tube with the engine running as the PCV valve purges crankcase vapors. If it feels more like a WOOSH than a sip, the PCV valve may be sticking open at times. As a vacuum reservoir, the crankcase would be the very largest one on the vehicle.

I had a V10 truck once upon a time that had sucked out its lower intake gaskets and was cavitating the crankcase without symptom, except for this noise much like what you've described. The 8-liter's noise was coming from the rear main seal, which was being made to vibrate like a musical instrument from the air being sucked past it.

If the noise is being caused by a vacuum leak from the intake manifold, a quick opening of the throttle blade once the engine is shut down will stop that in a heartbeat. Give that a try -- kill the engine and if it's wailing away, give it wide-open throttle to see if it changes anything.

Another vacuum reservoir is the brake booster. Pumping the brakes a few times will dump the vacuum and stop the noise quicker than if left to its own devices otherwise.

If the noise is electronic (and I keep going back to the coil failures), be sure that the key is all the way off first. If it is still making the sound, turn the key back on, just to see if it changes anything.

Like I said... interesting.


Customer: replied 2 years ago.
Thanks Ed. That is some good food for thought. I will check those things out. I was wondering if this could also be related to thermostat sticking issues as well. Could this also cause enough of a pressure build up to cause such a noise when the engine is shut off? Thanks Again.
Customer: replied 2 years ago.
I am also trying to get an audio file of the noise but it keeps hiding from me. Seriously, I have drove the vehicle 5 times today and the times that I didn't try to record the noise then it made the noise once the engine was shut off.
Expert:  Dodgerench replied 2 years ago.

That's something I hadn't thought of -- a singing radiator cap! If the engine is hot and the cap is venting when you shut it off, it's going to make that exact same noise. You'll be able to feel it in the cap itself, but don't dare take it off or things will get messy. Venting means it will be oscillating feverishly on the radiator, sending bubbles or fluid into the reservoir, so it should be pretty easy to distinguish if that's happening.

The thermostat won't be making the noise obviously, but anything that causes the engine to boil coolant sure could have a part.

Expert:  Dodgerench replied 2 years ago.

Just checking in. Any news?