My wife's 2017 Mustang with the EcoBoost engine had a bit of a problem. She had just gotten gas, and when she started the car, it would crank, not start. I told her to hold the throttle wide open and try to start it again. It started. I've known about the P1451 code for the purge valve, we've not replaced it, and that could be part of the problem, since it happened immediately after she got gas. The code indicates a biased/stuck rich condition exists in the car's oxygen sensors, though. Running, the car runs pretty lean as live data indicates, the long-term fuel trim is around 18%, it's almost ready to trip another code. She probably has vacuum leaks, somewhere. I'm not really familiar with that car's engine. The mechanical engineers decided to be cute, instead of live data being measured in grams of air per second, there's a pressure, and I really have no clue what that means. Every other car I've had has been grams per second. It measured 33 kPa, I'm assuming that's negative pressure, since 101.4 kPa is standard atmospheric pressure, and running cars suck in air. There's no easy conversion factor, so I think there's an unnecessary extra calculation, but I only have the minor in mechanical.
Since the root of the problem is most likely the purge valve, should I replace that first, as a good first step? Even that purge valve costs $78.
There's an extraneous code related to that capless fuel filler, but I don't believe that's relevant to the engine basically flooding out.
I fixed the purge valve assembly, she's taken the car and gotten gas a few times, each time, the car starts right up again. There needs to be a recall on these Mustangs. She's now on her third purge valve assembly in 7 years.
Her Check Engine Light will be coming on again shortly. There's a small EVAP leak from the capless fuel filler. That will need the entire gas tank taken out. Lucky we don't live in an emissions controlled area.
Since the root of the problem is most likely the purge valve, should I replace that first, as a good first step? Even that purge valve costs $78.
With those two codes I'd buy a new purge valve and then worry about EVAP. If that's what your asking?
Makes sense, it's what I would do first, based on the codes tripped. My wife thinks one of the oxygen sensors is bad, she's that type who says there's a code generated forthat problem,nso that must be fixed. She obviously doesn't work on cars.
since 101.4 kPa is standard atmospheric pressure
The standard atmospheric pressure at sea level is 1013.25 hPa, with standard air temperature 15°C and standard air density 1.225 kg/m³.
Actual air pressure varies with time and location, so do other 2 variables.
You need to know the actual values in your area to do accurate calculations.
That was just a back-of-the-envelople, educated guess.
101.4 kPa is what my professors use, since I don't know what the actual value is.
Density may be a little bit of an issue. The engine's displacement is only 2.3L. 4.9g/s it may be up to 20% off.
If is is, there's around an additional gram of air per second on the intake side.
That seems kinda high for an idling engine with no turbocharger. Scotty said it should be more in the ballpark of the displacement of the engine, not almost 6 g/sec. Haha.
Do you have a weather station nearby? Does it measure air pressure too? Density can be calculated too.
What value does the scan tool read in live data?
It's not rated in grams, unfortunately, that's why I was so confused at first. It makes sense after thinking a lot about it. When that turbo kicks in, the air density is greater, obviously, so you can't get accurate data from a conventional MAF sensor.
I didn't think of that, I'm near Lebanon, Ohio. We're around 1,000 feet above sea level. I'll hit up Google. Haha.
Interestingly, the weather station says it's 101.5-ish kPa right now. I might have to do the calculations again, because now I'm genuinely curious, lol. We must be experiencing high pressure.
I think the turbocharger does not play any significant role when idling. So the MAF sensor should show normal reading. You just need enough air and fuel mixture to move pistons. More air would result in more fuel injected for combustion. Consequently the engine would idle at higher RPM.
I knew the turbo doesn't contribute to idling, at least when the turbo has reached operating temperature. When I modified the air intake on my 2013 Fusion and converted it into a cold air intake, I'd hear the turbo kick in on high idle, and after around 30s, I'd hear hissing noise as the high idle came down. It was kinda cool. Haha. My wife's Mustang is all stock, and I can't hear the turbo when it spools up.
That's the thing, though. Live data only shows manifold air pressure in kPa, not grams of air. There's a Manifold Air Pressure sensor, not a conventional MAF sensor. Haha.
I did some brainstorming, and I believe the way the engineers designed my wife's car is unnecessary. Lol. I took standard pressure as 1 kg per square meter and divided it by the scan tool's measured 33 kPa relative pressure. That's 0.675 kg/ m2. I need to multiply by a time to approximate how much air it ingested in one second, since it's a volume. Using the fact it only ingests air every 1st of the engine's 4 cycles, I can calculate the results.
I noticed on the scan tool that the engine was idling at 800 RPM, so I divided that by 60. I got 14.33. I divided it again by 4. I multiplied that number by 0.675 kg/m3 and I got 4.9g/sec. All this for something that could have easily measured in the vehicle's coding in grams per second.
Anybody have any suggestions? I had some mega brain farts as far as liters of air, it's grams of air, so I edited it accordingly. Pre-brain cancer, I probably would have figured out the connection in 5 minutes. It took me about 2 hours to figure out again. The math is right. 4.9 g/s at idle.