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Model specific boards => Golf mk4 => Topic started by: pickles on 09 January 2013, 10:21
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engine losing power intermittently, very random, engine sounds very lumpy and misfires when problem is occuring
got this code tonight, been doing a bit of searching and im thinking my N75 is goosed, any1 had this code, checked all boost pipes and all appear fine, problems intermittent so thinking new valve.
would i be worth getting a J or H valve at all ?.
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new standard valve ordered from dealers, £40 odd fingers crossed :lipsrsealed:
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valves on and been looking good so far, will give it a few days yet tho :whistle:
Some info for anyone wanting to know about the N75 valve.
What the N75 valve does...
Found this on 20VTurbo.com ...
Here goes....
As i see many of you are totally confused about the N75 valve (what it does, how is it working), just exactly as i was before digging myself into the topic quite deeply. My car was seriously down on power - i even posted some desperate topics here too, but noone was able to give me any usable suggestions/answers. At the end, i found that there was some problem with my N75 valve (though it was working OK) which prevented the car to produce more boost than stock.
So, if any of you has problems with the N75 valve - or just got problems but don't really know what is it related to, then read more further.
The turbo, the boost it produces, the N75 and the ECU.
These are the most important things which you have to focus on. As we know, we got a turbo on our engine which produces boost. The turbo is "driven" by the exhaust gasses our engine produces. Exhaust spools up the turbine in the turbo which is mounted on the same driveshaft as the compressor which then generates boost. I persume it is all clear for everybody.
There is a wastegate on our turbos (as usually on every turbo) which looks like a simple valve, just exactly like in the cylinderhead. There's a difference though, the valves in the head are operated by the cams, the valve (wastegate) in the turbo is operated by pressurized air. When pressurized air is introduced to the wastegate, it will open, enabling the exhaust gasses to escape and skip the turbo. This will result in a dramatical loss of boost, because there will be no gas which would spin the turbo. I bet this is (was) also clear for everybody.
But how is this all hooked up???
Quite simply. The wastegate is operated by the turbo itself. The boost the turbo produces is directly fed to its own wastegate. What does this mean? When the turbo spools up, it will create boost and this boost will open its own wastegate, shutting itself automatically down.
But where's boost control? And wheres ECU?
Here comes the N75 valve. The N75 valve is inserted between the turbo's high pressure output and the wastegate. If the turbo would directly linked to the wastegate, it would not be able to produce lets say more than 0.3-0.4 bar of boost, because it would shut itself down immediately. When the ECU wants more boost (because you are stepping on it for example), it WENTS some air from this loop (turbo--->wastegate) so the wastegate will not open at all, or will open later.
The N75 has got 1 boost input, and 2 outputs. At the input, boost is entering into the N75 and exits on one of the outputs going to the wastegate. When N75 is closed (default state), all the boost goes to the wastegate. When ECU opens the N75 valve (because it has got an electrical plug too coming from ECU), so when ECU opens it, some of this boost (which would operate the wastegate) is leaving/leaking back to the inlet (and not opening wastegate). Since the N75 valve has NO state in between, is is opened or closed. The ECU switches it ON/OFF all the time (several times a second) to generate the desired amount of boost. Doesn't it reminds you to something???? ... Yeah, it's surging. But it is absolutely normal, this is how ECU controls the wastegate. When a car is chipped, the boost is a LOT higher than it is designed to operate on, so this kind of boost control will be noticable.
By adjusting the N75 valve, you can adjust the amount of air which should leave when the N75 is opened. If you adjust the N75 to the right, you will "close" the N75 valve, so just a few amounts of air is wented from the wastegate which will result in a lot smoother drive (eliminating surging, because the boost will be more constant), BUT at the same time it will introduce more boost to the wastegate, causing LESS overall boost. Adjusting the N75 valve to the left will "open" it, enabling more air to escape from the wastegate when N75 is opened, which will result in more boost (coz wastegate wont open), BUT at the same time it MAY cause surging as the N75 opening/closing will be more obvious.
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alls still looking well :), still not counting my chickens yet tho lol
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Sounds like it wasn't opening the wategate when needed. Misfiring would have been a way of saving the engine
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could a faulty wastegate also cause these symptoms. also i have vac line i think coming off the tip which goes to the throttle body via check valves etc. can i blank this off both ends at all.
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00544 code remains, i repeat 00544 code remains :angry:.
cars definately pulling alot better after changing N75 and problems did subside for a day :grin: however, had a small hiccup this morning and the code came bk, problems not anywr near as bad as before.
could the wastegate be sticking ?
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sounds like a coil pack issue to me
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how does the AGU measure boost if it has no MAP sensor?, im assuming its just values from various sensors.
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Via MAF, its a calculation. Using some factors and the MAF you can work out what the engine is doing at a given rpm and load. Later engines like AUM I've found a ball ache, you have the n112 and its friend, for controlling overboost and TC, drive by wire TB and the MAP sensor.
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so in reality it could be any1 of these sensors lol, think i might invest in vagcom shortly.
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would vagcom be able to read fuel system pressure as well as anything to do with the injectors.
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just too add i get the 00561 - Mixture Adaptation: Adaptation Limit (Add) Exceeded code as well but been getting this since i decated, comes n goes, still think iv a small leak in the turbo - downpipe gasket, going to get in about it today.
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is it safe to spray some wd 40 on the mechanical part of the wastegate?
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f**k it just bought a k03s :smiley:, il just upgrade the actuator for a forge 1
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guess what guys, changed my MAF n alls good lol :laugh:, was meaning to upgrade the cheap masterpro for a bosch for a while but it got me by for 4 months or so :)