p0299 underboost

[tubby]

Hi not been on Here in a while been busy trying to fix this car after having turbo done no better had new n75 checked pipework ok new maf good used tandem and diesel pump new intake manifold shudder valve timing belt done and new cam sensor as it devoloped this whilst diagnosing the lack of boost and general lack of turbo
the other and first thing changed the intake manifold control vac unit as not holding vac did not remove the intake to do,was gonna remove manifol to check the flaps is it possible they are jamming,also first thing I done was remove and clean egr looks like been changed before as found old gasket in engine bay, cannot here any boast leaks
,sometimes car drives quite well but not quite star kicking the it drivess in the. Next breath shot no go now on motor way at 70 to 80 get total lack of response limp mode but also feels like a nursery misfire to engine,when it drives at it's best the engine sounds free turbo whistling and when it drives **** it sounds muffled and noisey in intake like it's roaring please help at wits end I'm in the trade work for Cummins diesel tech and I can't work this out it's got me stumped unless it's something iv overlooked or wiring

 

[tubby]

Sorry it's a 2.0 tdi brd 07 manual a4

 

[tubby]

Sorry it's a 2.0 tdi brd 07 manual a4

Come on guys thought this was a forum not a cemetery

 

[desertstorm]

You seem to have covered a lot of the possible causes for an underboost condition, usually it will be related to N75, vacuum pipes , VNT mechanism sticking , boost hose / intercooler leaks or possibly EGR sticking.
Boost leaks are difficult to here just by revving the engine as it doesn't make that much boost when just sitting on the drive.
Check the vacuum you are getting on the turbo actuator at idle should be around 21-23 inches Hg.
You can do a lot more if you had VCDS by logging specified and actual boost, MAF readings etc.

16683/P0299/000665 - Ross-Tech Wiki

Karl.

 

[tubby]

Thanks for reply I really need to get this fix two yrs on and off driving me mad since Monday it's been driving quite well pulls up to red line not as strong as I would thought bit acceptable,but lasted 60 miles now driving hardly any boost comes in and fades out to none ,
I clamped the fuel return today no differance so don't think it's fuel related unless it's the lift pump in tank not up to the job.

 

[tubby]

Desert storm could really do with someone to stick with me on this as not come up with anything

 

[seanyboy]

Hi,ive been having the same problem but not as severe as yours .Ive read on another forum about the vacuum actuator on the inlet manifold not working fully so the flaps don't fully open on the intake manifold .
Ive just cleaned my egr valve and manifold today and its running a lot smoother but the turbo doesn't seem to kick in till 2k ..is this the norm range ???will give it a couple days then will try and replace the actuator if it doesn't improve .
hope this helps ..let me know if you solve the problem .

 

[tubby]

Turbo can be felt as low down as 1200 rpm in my car when it drives ok and when I say ok at it's best pulls to red line continues but stop feel it's a bit tame. Cause the other time is when I don't feel turbo infill 3000 rpm comes in then fades out of power .
I've done the inlet flap actuator. Was considering changing the turbo actuator but can't find one separate although turbo has been sent and returned by turbo technics. Now thinking flaps in manifold sticking but would it have such a dramatic effect on the turbo. I have vac tested the turbo actuator it moves quite a lot not measured. New n75. Got to hey a boost gauge to measure vac at turbo actuator.