Map Sensor

[Crickleymal]

recap so far. Changed fuel filter and found the ECU boost pressure sensor pipe frayed through so I cut the frayed bit off and reconnected it. Since then have been having numerous limp home faults which reset if the engine is switched off. I've replaced the MAF sensor and tried blanking the EGR valve. All no good.

 

I had the codes read on Monday and the only one, apparently, was the MAP sensor. If you blew/sucked on the pipe that I shortened it seems as though there was no resistance indicating another hole. So I replaced the pipe as far back as the accelerator pedal i.e from the engine manifold right back through the engine bulkhead to just above the pedals. Now if you suck/blow there is no leak. However the fault is still there.

 

The fault I now realise is not random. It will occur in exactly one of two situations. A] when you accelerate hard in 4th or 5th gear and when you get to about 3200-3500 rpm or B] if you pootle along on 4th or 5th at about 2-2500 rpm when it will slip into limp home mode without you realising until you have to accelerate. It will also occur with or without the pipe connected and seems to happen (although I'm not so sure about this) once the engine is less than cold.

 

I'm beginning to think a call to the Seat garage is called for. I'll have the ECU out at the weekend but as the fault is so specific I'm not sure what to do.

Edited February 8, 2012 by Crickleymal

[Crickleymal]

Silly question but all this happened after I changed the fuel filter. It couldn't be a dodgy filter could it. I know the codes say MAP sensor but the fault is consistent which doesn't really indicate a sensor failing.???

[zorgman]

and whats lurking about near the filter.????????????

thats right vacuum pipes, where does one of the pipes go ??????????????

to the map sensor.

get the codes erased first before reading as old codes are there then wait till you get limp mode then get codes read off so its accurate reading.

[Crickleymal]

and whats lurking about near the filter.????????????

thats right vacuum pipes, where does one of the pipes go ??????????????

to the map sensor.

 

Yes I know, I've replaced that pipe.

[cprob]

I had exctly the same problem. I changed every single vac pipe in the engine bay, stripped and cleaned the EGR valve, changed the MAF but it made no difference.

 

I finally replaced the 3" pipe that's inside the ECU (located behind the clocks in the dash) and it was fixed.

 

If you haven't done this yet, take out the ECU and change this pipe!!!!!!

 

Read all of this first and take note that a SECURITY T20 bit is needed and the job will be easy.

 

http://www.fordgalaxy.org.uk/ford/index.php?/topic/22717-how-to-ecu-removal/page__p__164798__hl__ecu+removal__fromsearch__1#entry164798

[zorgman]

just checked your asking the same question getting same answers as before, before going any further change the internal pipe inside the ecu as thats where your problem will be

[Crickleymal]

just checked your asking the same question getting same answers as before, before going any further change the internal pipe inside the ecu as thats where your problem will be

Oh yes I appreciate that and I will look at it this weekend. It's just that I can't detect any leak which I would expect if the pipe was broken and the fault is so reproducable that I wouldn't expect a split pipe to give identical results.

 

Malc

[cprob]

just checked your asking the same question getting same answers as before, before going any further change the internal pipe inside the ecu as thats where your problem will be

Oh yes I appreciate that and I will look at it this weekend. It's just that I can't detect any leak which I would expect if the pipe was broken and the fault is so reproducable that I wouldn't expect a split pipe to give identical results.

 

Malc

 

I couldn't detect a leak on mine either by sucking on it. But remember, this pipe is under pressure not vacuum and it only takes a tiny hole to cause problems. My pipe had a very small split so when I sucked on the other end of the pipe the split just stuck together and the pipe held the vacuum with my tongue over the end (yuk). Under pressure (blowing into it) the split opens up and causes the limp mode and you won't detect this very small leak by just blowing into it!

 

I look forward to your next update AFTER you've changed the pipe inside the ECU!!! ;-)

[zorgman]

itll be all claggy and gooey, make sure you use the proper pipe its the same cotton covered stuff thats used for leak back on the injectors. if you've not got any left you only need approx 2" which you can take off another vac pipe that has a bit spare

[nicebutdim]

Don't forget the turbo can boost up to (and over) 15 psi, can you blow 15 psi? It's bit of a pig to get that ecu out, but stick with it and it'll free up eventually!

[zorgman]

be prepared to get cuts on hands the metalwork is very sharp in there, if i think on the big plug uses a slide action on it and module on top is bulb fail unit, just take your time an do it methodical. youll need a a torch and a mirror to see where the 2 torx bolts are the keep the ecu onto its bracket these are at front where plug is, forgot now how i wangled out.

[Crickleymal]

As I suspected it's nothing to do with the piping. It was all as clean as a whistle and even when I replaced it all it made no difference. Doesn't seem to be the N75 solenoid either.

[zorgman]

you need to get vagcom onto car and do some testing as theres only so far we can go in helping out remotely