Felix R Cepeda

Hello everyone,
I've been having stalling issues with my mustang, I have a 2010 V6. The RPM gauges fluctuates a lot between 500 to 1200 RPM until the car dies, it is not a constant issue but it is getting often. The RPM gauges also fluctuate at higher speeds any speed but the car doesn't die unless at Idle. I have codes for EGR low flow, Evap purge circuit, O2 sensor heater circuit (all O2 sensors), Engine running rich bank 1 and bank 2, EGR circuit.

I have reset all codes multiple times and they all comeback. I have done the ECU reset by touching both positive and negative terminal of the battery while disconnected. EGR has been replaced twice, last time done by dealership about 200 miles ago, O2 sensors were replaced about 5k miles, and Evap purge valve was replaced 2k miles ago, new MAF 3k miles, and new battery 1k miles ago, no positive changes with any parts replacement. I tested the body of the car and engine to the negative battery lead testing for continuity and test was good both with engine off and running.

Car runs fine with MAF unplugged after car goes to Limp mode, it doesn't stall at all or have any issue while on Limp mode.

Engine was vacuum leak tested, and all vacuum hoses were also tested with no leaks. Sparks plugs, fuel injectors, fuel pressure, were all checked good.

Any ideas ?

08'MustangDude

If the EGR is stuck open, the car will stall at idle, due to a vacuum leak
at idle.

Just had someone with an issue like yours, his idle was fluctuating, and
had an O2 sensor code. He had it replaced, that stopped everything.
I had never had an O2 sensor cause issues like that, but that is what it was.
Code was also there for a rich condition, bank 1.

Yeah, driving it was okay, but when he pulled up, and stopped, you could
hear the up and down idle... It didn't stall though, just idled up and down
like yours. So, yep, once he had the O2 sensor replaced, it was fine.

Felix R Cepeda

My EGR has been replaced 3 times., the first time I got the EGR low flow code I bought a new one from auto zone but the problem persisted, then I return that cheap one from auto zone and bought a new one from ford dealership, after installing that one the problem persisted so I took the car to ford dealership to have them diagnostic and they came up with bad EGR just by reading the codes, at this point I knew something else was probably causing all those codes to come up at once but they insisted it was an EGR problem, I let them replace it and of course the problem still there, with all the codes and the same issues. Car runs fine when on limp mode but as soon as I plug in all sensors the problem returns. I'm thinking I could have corrosion on my SJB due to some water intrusion, I discovered that drain plug by the passenger side firewall was clogged with all kinds of things not letting the water to drain and once the water got high enough it was leaking into the passenger cabin right on the SJB. I don't know how long I had that issue, but I think it probably went for long enough to cause corrosion then causing all electrical problems I'm having. Any toughs?

08'MustangDude

The leaking is a common issue with these cars, and a bad design flaw.
They should be recalled, and the drainage updated.

I am out of ideas...