MAP sensor accuracy test - Ford Focus 1.6 16V Zetec SE
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- Опубліковано 18 лип 2016
- I've been racking my brain for quite a while now trying to solve a lean idle condition and high positive fuel trims at idle on this car. No vacuum leaks could be detected (though this is a speed density engine, so a vacuum leak really shouldn't influence fuel trims much) and nothing seemed obviously wrong, yet the car was generally running quite lean at idle and basically whenever the vacuum was high (like while engine braking).
Well, it seems like I've finally found the culprit. Looks like the MAP sensor readings get progressively more out of calibration the lower the intake manifold pressure gets. At idle, the MAP sensor is reading around 4-5 kPa lower pressure than it should according to the vacuum gauge - the vacuum gauge is reading around 29-30 kPa of absolute pressure (so around 21 inHg of vacuum for the people using the imperial units), but the MAP sensor actually reads 24 kPa. So it's quite obvious the ECU tries to lean out the fuel mixture, since it sees less air than there is, and then has to correct that leaning by high positive fuel trim to get back to stoichiometry.
Interestingly enough, at higher pressures, the calibration error seems to disappear and at around 40 kPa of absolute pressure (and above), the readings are pretty much correct, leading to an issue that mimics the classic symptoms of a vacuum leak (but again, this is a speed density engine, so the fuel trims should not be affected much by a real vacuum leak, unlike a mass airflow engine).
Sadly, Torque Pro is quite slow to react and also lags a bit behind, so it doesn't show how low the MAP readings actually go when you rev the engine to something like 2-3k rpm and then go off the throttle - the vacuum gauge dial doesn't really drop below 18 kPa, but the MAP readings (when using a faster scan tool like Forscan) can momentarily go as low as 9-10 kPa at that time - which is actually the lowest pressure the MAP sensor can detect, according to the specifications.
Also, please ignore the "Vacuum" dial - I have no idea what the reading it shows is, it's certainly not the amount of vacuum the engine is pulling. Just look at the "Intake" reading, that is actually what the MAP sensor sees. To get the amount of vacuum the engine is pulling at the time (in kPa), just subtract the "Intake" value from 100.
So yeah, guess I need a new MAP sensor.
Hello!!! , do you know where the MAP sensor is located in this motor??? i have a zetec 100 cv 1.6 like yours, and it runs very lean, so slow and a lots of jerks while i acelerate, and at idle it shows 23Kpa on dyagnosis, do you think i have a bad sensor too? i tried to locate it for cleaning but i dont find it! sorry for my bad english, cheers!!!!
If it's the same engine I had on this car (there are several versions of the 1.6 zetec, so they might be somewhat different), then the MAP sensor was placed rather awkwardly behind the plastic intake manifold on the front side of the engine. Standing in front of the car, you can see the MAP sensor connector in the gap between the first and second intake from the left. You can even reach it with a bit of an effort, but if you want to replace the sensor, you need to remove the alternator (which is right next to the intake manifold further to the left).
But I would probably advice against trying to clean a MAP sensor, it's unlikely it needs cleaning (on a petrol engine, at least) and attempting to do so might do more harm than good.
@@Case_ Thanks you very much!!!!, i will try directly to replace it, it is not so expensive, i was so crazy about don´t finding it, thanks really man!!!
Hi, i read your thread on the ford owners club forum. What was the make of your new sensor? From so many aftermarket makes i don't know who was/is their original oem supplier or who makes the most accurate sensor.
The new sensor was from EPS, simply because I could get it for a very good price at the time. Not sure how accurate it iss or who makes the OEM sensors, but no issues with this one (at least not any I am aware of).
Hello,
I think I have the same problem, decalibrated MAP senzor. For example I dont get 0 mpg and engine brake only if I let the throttle over 3000 rpm, this mean that the MAP is reading the vaccum only then...
Did you solve the problem with the MAP repalacement?
Thanks
Sorry, I don't understand what it is you're experiencing from your description.
However, yes, I did solve my issues by changing the MAP.
In my 2003 Focus ST170, I cannot find out the MAP where it is located. However, I have similar problem as your video. I use a physical gauge can indicate -20inHg at least after warm, but OBD2 feedback is only -11inHg (never up to -14 anymore) and recently get worse fuel consume including difficult start up with too rich appearance. I am confused to do the troubleshooting.
Don't know much about ST170, but are you sure your engine uses MAP? It's kinda more common on these vehicles and engines to use MAF, in which case it would be located somewhere near the airbox on the main air intake.
@@Case_ This is the main question as same as you. In electrical manual, ST170 of diagram does not have MAP in circuit. It only has MAF and Barometric(BPS), and TPS sensors in system. Although I have tried to disconnect each of them, vacuum(boost) in obd display does not change any different values. This is why I try to find the something like MAP device at intake manifold body. However, it cannot find out anything and be very confused.
@@Case_ Hello I've been searching the MAP Sensor on my 2006 Ford Focus 1.6 16V can you please pinpoint the location where I can find the MAP Sensor, I'm kind of confused now. Thanks!
@@wildventures8409 If your Focus has the same 1.6 74kW Zetec like mine had, then the MAP sensor is quite awkwardly located kinda behind the intake manifold on the left (standing in front of the car looking at the engine), next to the alternator (which I had to remove to replace the sensor). If you look through the gap between the leftmost intake tube and the second from the left, you should see the sensor's connector and the wire in a plastic sleeve through there.
(Then again now that I think about it more, 2006 is already Mk2, isn't it? In that case it has an upgraded version of that engine which Ford called Duratec instead of Zetec (SE), and I'm not really familiar with that one...)