Hi guys,

I’m writing this post to explain the problem with my Focus 1.5 TDCi. I’ve been driving it with this issue for about two months and I feel a significant loss of power. I found a video on YouTube and tried unplugging the MAF sensor, and magically the car runs perfectly, just like I remember.

So, can I be 100% sure that the MAF sensor needs to be replaced, or could it be something else?

Also, I drove about 100 km with the MAF unplugged and the engine light never came on.

This is the video I saw, and it explains the same problem I have… but in my case the IAT values is ever the same as the ambient temperature (when the MAF is plugged)

https://youtu.be/-I593guHgL0?si=k249jBb7_wjf4dFb

 

thanks so much!

1 hour ago, Mirko29497 said:

So, can I be 100% sure that the MAF sensor needs to be replaced?

No.  The engine just runs in a default failsafe mode with the MAF unplugged.  This test just masks other faults.

54 minutes ago, TomsFocus said:

No.  The engine just runs in a default failsafe mode with the MAF unplugged.  This test just masks other faults.

Which other component should I test? Before to do this tests, there wasn’t DTC in memory

3 minutes ago, Mirko29497 said:

Which other component should I test? Vedere do this tests, there isn’t DTC in memory

It could be many components, we need an idea of where to start from a fault code.

If you don't have an EML/CEL showing then there won't be a code on a normal garage OBD reader.  Need a Ford specific reader to read the hidden Ford codes.  Forscan is best if you can access that where you live.  Otherwise it'll need to be a Ford dealer, but that won't be cheap.

If you don't want to pay for a Ford test and can't access Forscan then the cheapest option would be to replace the MAF and just hope that does fix it.

Quote

Forscan is best if you can access that where you live.  Otherwise it'll need to be a Ford dealer, but that won't be cheap

I use Forscan to read the DTCs but there aren’t…

20 minutes ago, Mirko29497 said:

I use Forscan to read the DTCs but there aren’t…

That is very strange.  In that case, it's very difficult to avoid risking wasting money on a fault like this.

I don't suppose you have a friend or relative with the same engine model?  If you could borrow their MAF then you could test it on your car without risking wasting money on a new one.  

If not then you could take a live data graph showing the MAF readings when the MAF is plugged in.  I don't know the readings off-hand but other members do if you're able to get those.  One at idle and one at 3000rpm should give us a good idea.

You can also do a graph with both MAF and MAP sensors showing.  Both lines should be very close.  If the MAF is faulty that will often be slow to react or stay very low instead of following the MAP reading.

All I can say is for 2l as a starting point:
At idle, Forscan gives 8.62 g/s
At 3000 rev/min (no load) it gives 77 g/s (although diesels always take a  full cylinder of air, or should?)

33 minutes ago, Shearers said:

although diesels always take a  full cylinder of air, or should?

In the distant past, yes. 

However, with a turbo you'll get more than a full cylinder of air on boost. 

And with an EGR valve open & air doser partially closed you'll get less than a cylinder full of air at low load.

So, a short while ago I ran some tests at idle and at 2,500 rpm (I couldn’t push it any further because I would have disturbed the neighbors), and these are snapshots of the data. Unfortunately, I didn’t manage to obtain the data from the oscilloscope

2 minutes ago, Mirko29497 said:

So, a short while ago I ran some tests at idle and at 2,500 rpm (I couldn’t push it any further because I would have disturbed the neighbors), and these are snapshots of the data. Unfortunately, I didn’t manage to obtain the data from the oscilloscope

There is something wrong with FORScan's MAF Desired, I can assure you it shouldn't be 52 at Idle.

When you posted this I was about to post that I would expect between around 5 and 9 g/s at Idle. Higher Rev figures should be taken while being driven to be meaningful and as Tom said the MAF and MAP should follow each other.

If you have saved the Live Data then you can view it back in the Oscilloscope or Dashboard form in FORScan as well as Table. 

1 hour ago, Tizer said:

There is something wrong with FORScan's MAF Desired, I can assure you it shouldn't be 52 at Idle.

It can be the MAF fault?

Tomorrow i will try again and save the graphics

1 hour ago, Mirko29497 said:

It can be the MAF fault?

I think FORScan is showing the correct Actual MAF figure in g/s, but the Desired looks like it is in pounds/hour, certainly at Idle. 1 g/s =7.936 pounds/hour. The higher Rev figures do not does not convert though.

The difference may be because the car is stationary but I'm not sure about that, I do know that the figures you get for things like Fuel/MAF/MAP etc when revving a stationary Engine are completely different to the ones you get when driving.

10 hours ago, Tizer said:

The difference may be because the car is stationary but I'm not sure about that, I do know that the figures you get for things like Fuel/MAF/MAP etc when revving a stationary Engine are completely different to the ones you get when driving.

It's almost as if cars are mapped to produce lower emissions when on a stationary test rig...  

I agree though, 2500rpm stationary isn't a great test.  There may not be much boost in that situation.  3000rpm on the road is a fairly safe bet for producing boost.

Hi guys,

Some minutes ago, i have do the test on a runway with the 4° gear e cruise control active to remain in 3000 rpm. Down you can see the test...

On a quick look, the desired and actual MAF are miles away?

With demanded being higher i.e. about 200g/s (with my 77 g/s not looking too silly) and the actual being 47g/s (Ha Ha!) it looks to me like MAF or wiring needs serious inspection and testing or summat else to get MAF up or correct as that difference is an issue??

 

The car has 240,000 km. From what I’ve seen online, another suspect is the EGR — I think it was never cleaned. The previous owner may have tried to remove it, because one of the Torx bolts on the valve is stripped, and I don’t know how to remove it.

Could it be that too?

I still say the Desired MAF is wrong, I don't think it is possible to squeeze 200g/s of air into a 1.5 Engine at 3000 rpm even if the Turbo was boosting to it's full capacity, which it wasn't.

What Tom meant in his earlier post was to graph the MAP and MAF to see if they follow each other in normal driving, not at constant Revs.

I did notice from your Screenshot that the MAP was a bit wavy although it is difficult to tell from a static picture how much it is varying.

I'm sure that if the MAF was giving spurious readings you would get a Fault Code.

37 minutes ago, Tizer said:

Continuo a sostenere che il MAF desiderato è sbagliato, non credo sia possibile immettere 200 g/s di aria in un motore da 1,5 litri a 3000 giri/min, anche se il turbo fosse alla massima capacità, cosa che non è avvenuta.

Ciò che Tom intendeva dire nel suo post precedente era di tracciare un grafico della MAP e della MAF per vedere se si susseguono durante la guida normale, non a regimi costanti.

Ho notato dal tuo screenshot che la MAPPA era un po' ondulata, anche se è difficile capire da un'immagine statica quanto vari.

Sono sicuro che se il MAF fornisse letture false, riceveresti un codice di errore.

Ok, anyway, I’m sharing the full test in case it might be useful. I started from home, went through an intersection and a roundabout, and then got onto the highway. I took the same route back to return home

8 hours ago, Mirko29497 said:

Ok, anyway, I’m sharing the full test in case it might be useful. I started from home, went through an intersection and a roundabout, and then got onto the highway. I took the same route back to return home

The Actual MAF looks fine to me, the MAP looks a bit unsteady.

I can't remember seeing a wavy MAP line before.  Not sure what's caused that?

If you can condense the graph down to show more time then we'll be able to see whether the MAF and MAP lines rise and fall together while revs change.

For the Maf_DSD issue, could it be caused by the MAF sending an incorrect signal to the ECU?

9 minutes ago, Mirko29497 said:

For the Maf_DSD issue, could it be caused by the MAF sending an incorrect signal to the ECU?

No.  Desired MAF is the 'stock' figure inside the ECU.  That can't be changed by MAF signals, the MAF signals get compared to it to test whether the MAF is working.  The desired MAF could be affected by other sensor inputs such as incorrect MAP signals.

You are also correct about the EGR pipe clogging up badly on this engine which does affect airflow readings.

11 minutes ago, Mirko29497 said:

For the Maf_DSD issue, could it be caused by the MAF sending an incorrect signal to the ECU?

I don't think so, FORScan is not perfect.

If you know someone with the exact same connect up FORScan to their car and see what it says.

Guys, I really don’t know. This morning, after yesterday’s test, the car was running fine. As soon as I got back home, I immediately checked the values on Forscan and they’re the same as the ones shown. Fed up with the situation, a few days ago I bought a brand-new original Ford MAF, which still hasn’t been shipped, but given the situation I’m about to cancel the order (I was hoping it was the problem, since the car was running fine without the MAF).

The only other thing I would say is the the Turbo (MAP Reading) maxed out a tiny bit earlier and higher than I would have expected although not enough to be a major concern unless it maxes out higher than the 255 it did on the Screenshot.

I always thought that the high 240's were normal for that type of car but I maybe wrong about that.

Could someone in the past done something to the Turbo to get more power or fitted a Blow Off Valve or something like that?, like Tom I have never seen a flutter in the MAP Readings before.