Shimsteriom
Master Procrastinator
I thought that if it ran the same with or without the MAF connected, that it suggested a duff MAF as the ECU was running with it's defaults? 
sierrafery
Well-Known Member
Can be a clogged CAT if it still has it or it ran much without air filter and sucked in much dust the compression can be low as well due to worn piston rings... i'm wondering how well it was serviced though if you just realised it doesnt have a filter
go somewhere where the noise is not an issue, undo the downpipe from the turbo and make a drive test ...if it will have good power this way fit e de-CAT downpipe
sierrafery
Well-Known Member
If you want to bypass the modulator you have to take the pipe which runs from intercooler to the bottom port of it and connect it to the actuator valve but i doubt it's that cos the symptom you described doesnt look like overboost at all
sierrafery
Well-Known Member
overboost, it would be ''agressive" with good power up to max 3000 rpm then cut fuelling for overboost protection then regain power after few seconds when the rpm drops and so on... better concentrate on that flow thing in the exhaust first
sierrafery
Well-Known Member
Eyeballing those sensors without a tester won't help much though
Yeah it is. Often I've found its the MAP sensor. If you measure the output, idle should be about 2v if I remember corectly. Full load was about 4.3v (1.2bar) I think. Don't count me on those figures, but its a start to the diagnosis.
brian47
Well-Known Member
There seems to be an element of confusion here. The MAP sensor is mounted on the inlet manifold, that's the "Manifold Absolute Pressure/inlet air temperature sensor.
The MAF is built into the air pipework between the air filter and the turbo. It's the Mass Air Flow sensor.
The sensor to which I think you are referring is the Ambient Air Pressure (AAP) sensor which is mounted in the side of the air filter box.
I'm talking about the MAP sensor and the AAP. If the AAP is disconnected, the ECU controls the pressure at 0.9 bar.
If the MAP sensor reads wrong, the fueling calcs go all funny and it feels like its gutless. Alot of more modern vehicles seem to use the MAF for fuel calcs, but this one seems to use the MAP.
Heck the ECU could think its at 1.2bar already when in fact its only at 0.2 bar.
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sierrafery
Well-Known Member
Actually the default for AAP complete failure is boost limited to 1 bar though the OP didnt report black smoke and for both AAP or MAP failure in most cases black smoke is present under hard throttle cos when they start to fail the readings are going lower not higher so the ECU compensates for the presumed lack of boost (based on the low reading) with more fuel... though IMO these things can't be properly diagnosed without tester or going the rudimentary way by replacing them with new or known good ones and hoping this would fix things
