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Discussion Starter #1 (Edited)
hi every one! I'm new here, but hope i will get allot ideas and knowledge from you. so here is my issue with my 320d (136bhp) i bought it a month ago and on the way home i noticed when you accelerate hard it start pulling well but at around 2000rpm it suddenly loose power and start picking up again. so far i have changed
breather filter
maf sensor(Bosch)
replaced 3 vacuum hoses
cleaned egr valve
inlet manifold sensor cleaned
had plugged on computer(no errors)
done a boost leak test (holding 1 bar with no leak)
now i still have all the plastics of from engine and had a go to see if something changes to better. i noticed (heard) that as soon engine start getting full boost (around 2000rpm) pressure drops! i heard noise sort of dumping air out like on petrol turbo cars. and then engine start picking up boost again.
so a question is what not letting to get fool boost? thank you very much if some one can give ideas or experienced similar problem
 

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I know the later M47TU diesel manifolds were prone to splitting, have you done a visual on the engine especially when someone revs it up for you?
It does sound like its "loosing" boost but as you say you've pretty much cleaned and changed everything, BTW has the boost sensor been checked electrically just to confirm it hasn't failed?
 

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Discussion Starter #3
I know the later M47TU diesel manifolds were prone to splitting, have you done a visual on the engine especially when someone revs it up for you?
It does sound like its "loosing" boost but as you say you've pretty much cleaned and changed everything, BTW has the boost sensor been checked electrically just to confirm it hasn't failed?
i haven't checked it electricaly 'cos have no tools to do that, just cleaned it with carb spray. and for manifold it self it's less likely because it's drops boost all of the suden and then pickin up again,and you can hear it. to me like through air filterdumping out, but that noise very short time split of the second. but as you say it's worth it to check visualy and cost nothing. thank you for ideas.
 

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Could be sticky vanes? It's the most common thing with regard to boost issues, soot build up is the problem.
You could try moving the actuator arm manually to free it up a little. Could possibly even be a fault with the actuator itself?. You can check both the vanes and the actuator properly with a mity-vac.
 

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Could it be building to much boost at the lower revs so the system dumps it ??,leaving the turbo to then rebuild the boost back up.
 

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Discussion Starter #6
Could it be building to much boost at the lower revs so the system dumps it ??,leaving the turbo to then rebuild the boost back up.
i wish! in that case it should be pretty fast then, but it's not.... I'm just thinking about that actuator, it's controlled by vacuum, so it must be diaphragm inside, so maybe it's broken and cannot hold certain pressure and actuator arm keeps opening wastegate when it shouldn't. or I'm wrong here?
 

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so maybe it's broken and cannot hold certain pressure and actuator arm keeps opening wastegate when it shouldn't.
Yeah it would be sticking open? These have variable vanes rather than a wastegate George. Both work the same way but the vanes on these get clogged up with soot and tend to stick.

Get some pliers and try moving the actuator rod up and down. Should be at least an inch of travel.

You can also try testing the actuator by sucking on the vac pipe, doubt you'd move it far though :hihi you really need the proper suction tool to test it.
 

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Discussion Starter #8
Yeah it would be sticking open? These have variable vanes rather than a wastegate George. Both work the same way but the vanes on these get clogged up with soot and tend to stick.

Get some pliers and try moving the actuator rod up and down. Should be at least an inch of travel.

You can also try testing the actuator by sucking on the vac pipe, doubt you'd move it far though :hihi you really need the proper suction tool to test it.
thank you for advice I'll try to see if that arm moves freely, if it's not that mean it could be sticking as you said. i realy hope that will solve it, i don't want end up taking turbo out. no replacing it! by the way engine is 160k on the clock so could be allot of soot in there.
 

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Discussion Starter #10
If you're any good with a spanner, cleaning the vanes is quite easy. Taking the turbo off itself is the hardest part. :thumbsup
cheers, but i think i better not take it out, i don't want end up with broken rusty bolt and nuts on manifold. or it's some how easy then on Audi's? i had taken of few times on my quattro. but it's a big job i would say. but of course if will be no other choice i will. but hope i don't need to. so more or less it shoud be sticking vanes?
 

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Discussion Starter #12
Pretty much the same really, they both use garret turbos, assuming you mean the A4 chassis.
no i have wide body quattro and it's kkk26 turbo in there. so when i took it out i broke all rods in manifold, had to take manifold out, drill it out and put new ones in. but htat was 25 years car so it is understandible.
i never had a diesel before so maybe some of the thoutghs abit :duh
 

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Discussion Starter #13
I'm not having any luck ! inspected that vanes arm on turbo it's moving OK. and when you have engine idling i took vacuum horse of from it, so it comes out, plug back in goes all the way in. sad but nothing helped so far .:mad if somebody can share more ideas ll'be nice.
 

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Block off the egr valve to rule out any pressure being dumped back to exhaust system.

Not sure at what revs they finally close but you have tested most of the other stuff and it may explain the 'dumping sound'.
 

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Discussion Starter #15 (Edited)
Block off the egr valve to rule out any pressure being dumped back to exhaust system.

Not sure at what revs they finally close but you have tested most of the other stuff and it may explain the 'dumping sound'.
that make sense. what to use and how to block it off? i never done this before. i just heard that is some kind popular mod on diesel engine
 

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Remove the vac pipe from the EGR and plug the pipe, a golf tee works wonders :D, it will disable the EGR.
If you find this succesfull I would slightly alter the mod for the long term by plugging both vac pipe and EGR actuator pipe or fitting a bypass kit.
 

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Discussion Starter #17
thanks i will try this today, hope it will help. it drives me mad i even was dreaming last night about it. and that is wrong!
 

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Discussion Starter #18
Remove the vac pipe from the EGR and plug the pipe, a golf tee works wonders :D, it will disable the EGR.
If you find this succesfull I would slightly alter the mod for the long term by plugging both vac pipe and EGR actuator pipe or fitting a bypass kit.
done that no luck. i even had a video taken with my iphone fixed under the bonnet with little light. and that proved that actuator arm opens vanes at some point and then closes again. so under full throttle vanes open and lets pressure boost to escape for some reason. why it happening like that?:frown
it's done by ecu unit or faulty part. but which one? any ideas will help guys!
 

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Discussion Starter #20
Have you isolated where the pressure is escaping from?
i think the presure goes back to exaustor through filter , 'cos on the video i took i can see that actuator arm pulls out and then you can hear the noise of air escaping. and then closes again. and start picking up boost. i'm going to see machanic tommorow, i have no other ideas what to check! :mad:mad:mad:mad:mad:mad:mad
 
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