Maf Sensor And Turbo Questions

[ianyerman]

hi, have a few questions about the maf sensor,

will keep this simple, seat alhambra 1.9tdi 115, I dont drive this car much, wife does

was driving it on family day out, was stuck behind a car for about 10 miles doing about 40mph, went to pass it noticed it was in limp mode, switched off and restarted engine but went back into limp mode, about 2 miles later turbo blows, smoke everywhere, got the car home (about 5 mile so drove it)

stripped turbo put new center core in cleaned vnt rebuilt all into car, all going great took for test drive all smoke cleared, car felt very sluggish and no power, noticed car trying to boost but unable to, feels like something holding it back, engine just cant rev freely.

noticed turbo wisle and then stops when goes into limp mode vag com says 17964 charge pressure control negative p1556 - 35-00

checked turbo waste gate and all fine, all vacum pipes fine. removed exhaust incase cat was blocked still the same, removed and cleaned the egr valve and still the same

no other faults showing up on vagcom, when you unplug the maf sensor it shows up as a fault and same with the map/temp sensor

 

was woundering if a faulty maf sensor shows up on vagcom or not as its still giving a signal just the wrong one?

also would it have been possible for me to have built the vnt wrong or is there only one way they can go, they are moveing as i double check this when building the turbo

 

wife just informed me the car has had no power for a few weeks before this all happened so the problem could have been there before the turbo problem.

[Mirez]

A failed MAF won't usually show a fault code but definately won't throw the charge error. Not sure if it's possible to rebuild it incorrectly but that code is normally associated with sticking vanes so check the vacuume pipe, diaphragm, and even the valve.

[ianyerman]

think the charge error is comming on because the maf is not letting the fuel in as its not telling how much air its getting which is not letting the turbo boost then when you rev it on out its under boosting which throws the fault up, doesnt go into limp mode untill you rev it on out. at low rpm it feels very sluggish as if there is something restricting the exhaust / airfilter

wife informes me that it like shuttered a few times before the loss of power started a few weeks ago

[Mirez]

think the charge error is comming on because the maf is not letting the fuel in as its not telling how much air its getting which is not letting the turbo boost then when you rev it on out its under boosting which throws the fault up, doesnt go into limp mode untill you rev it on out. at low rpm it feels very sluggish as if there is something restricting the exhaust / airfilter

wife informes me that it like shuttered a few times before the loss of power started a few weeks ago

 

Hummm, I suspect that's probably not the case but disconnect the MAF and drive it - you'll be within tolerance with the MAF disconnected as it'll use a default map so if you still get the charge code then its not the MAF.

[ianyerman]

If I clear fault codes wife can drive car all day with no fault code, just says it has no power, only throws up fault code when I drive and try to rev it out, turbo vanes moving ok as when up on ramp and someone in the car reving it you can clearly see the control rod moving,

[ianyerman]

worked out how to data record via vagcom and went for a drive, maf readings are way out from what the ecu is looking for. going tomorrow to get a new maf sensor and hope this sorts the problem.

[bfc1001]

i had this fault a few months ago , negative pressure 17964 and it turned out to be a split pipe to the bottom of the turbo . i did a vag com test on my maf sensor (before i sussed it was a split pipe) and the max reading i got was about 550ml of air no matter what speed or rev s i was doing. when i repaired pipe and then re tested the maf it read 1100ml . what im sort of saying is if your car is in limp mode u wont get an accurate reading of your maf from vag com. id consider giving your maf a clean first and maybe checking voltage before u start shelling out money.

[ianyerman]

got new maf sensor today, could only get an intermotor 19600 sensor, right one listed for my car, turbo is now kicking in but not until about 3000rpm and with a bang, no limp mode or fault codes anymore. starting to think i have built the vnt togeather wrong, its moving freely as i checked all of this when building turbo, also when you watch the acutaor arm while reving the engine its moveing so the vacum is working

[ianyerman]

checking the vacuum pipes and noticed the n75 boost control valve is very very warm, is this normal?

[ianyerman]

problem sorted, turned out to be fuel temp sensor and wasnt showing fault via vagcom, just giving a duff reading to the ecu

[harpster]

problem sorted, turned out to be fuel temp sensor and wasnt showing fault via vagcom, just giving a duff reading to the ecu

can u tell me how you established it was fuel sensor

thx

[Trislander]

????

[chrispb123456]

????

You really need to check vacuum hoses to the turbo, and the air charge  hoses + intercooler, have you tried working the actuator on the turbo incase it's stuck up.