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Dread91

Over and under boost (p0299,p0234)

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Looking for some advice on an overboost and underboost problem on my mk2.5 1.6 tdci.

Was driving down the motorway when I had an engine malfunction warning come up on the led display. Lost all power and couldn't go faster than 40mph (guessing limp mode) but no EML light. Got of the motorway and turned the car off and on again, car was back to normal. Just before I got back home the EML came on but not loss of power.

I plugged the car into forscan and read the codes P0234 overboost and P0299 underboost.

The only other information I can give is that I can hear a faint whistle/whine noise from the engine bay, I'm no expert but it almost sounds like a leak maybe to me. Other than that I know I have a leaking injector 1 seal if that could be the problem?

Any advice would be much appreciated thank you .

Dread

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Sorry one last thing,

I ran live data of the maf and map sensors.

Maf looked all okay to me (again no expert) but the map was running around 100kpa at idle and rose to to 106kpa when snapping the throttle, then dropping to 90kpa before going back to 100kpa. That's doesn't sound correct to me, so maybe a bad map sensor or something causing that reading (assuming it is a bad reading)

Thanks again

 

Dread

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The MAP should momentarily read close to 250 under extreme load with the car moving. Measuring it with the car stationary does not tell you much.

I would carefully check for air leaks before suspecting the sensor or Turbo. 

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Unfortunately I have to keep my laptop plugged in because the battery is knackered so I cant drive and test.

Are there any specific places I should be checking for leaks?

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It could be anywhere, possibly the Intercooler. If it is a leak then it may not be obvious until some pressure has been built up and may be heat dependant.

The phone App is a lot better for logging live data. If you don't have a wireless adaptor it may work with an OTG cable if you have one and your wired adaptor, although I have never tried. I think you can download the free Demo phone version to check but you would need the paid version if it does work.

 

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Have you had the fuel filter changed ? 

I've experienced issues before with engine warning and sudden loss of power then surges followed by cutting back again

Had fuel filter changed and all was fine 👍

I too was thinking turbo or intercooler but was just fuel filter in mine.

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Going to get under the bonnet today and check all the pipes, so fingers crossed I find something.

My fuel filter is in need of changing and i do have one already to put in but would a clogged one cause an overboost/underboost code to show?

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Is it a 90 or 110?  It sounds like sticky VNT vanes to me, but that's not such a common issue on these.  Of course, if it's a 90ps model then that would rule out any VNT issues, and I'd suspect the wastegate solenoid instead.

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It's a 110.

Can I test to see if they are stuck with the turbo still on the car?

Thanks

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2 minutes ago, Dread91 said:

It's a 110.

Can I test to see if they are stuck with the turbo still on the car?

Thanks

I'd suggest they're sticky at the ends of travel rather than actually stuck solid so a bit more difficult to diagnose.  I can't remember if there's enough access space to remove the actuator arm or not, I think the oil feed pipe might be in the way but you'd have to have a look unless someone else can confirm.  If you can get the actuator arm off easily, then it's simply a case of moving the vane arm with your fingers to see if it's got full travel and feels smooth & free.

 

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So just been under the bonnet, checked all the hoses around the turbo and intercooler for splits and couldn't see any. The only thing I could see was the metal pipe that goes to the intercooler had a fair bit of rust but couldn't see any holes of any kind.

I unhooked the actuator arm and tested the area it connects to for movement, I could move it easily but noticed it didn't travel far and from what i have read on the internet is that it should move more than a half inch? It can move all the way down because it physically cant go any further as it hits an adjustable screw but as for up I can only assume it goes all the way because it meets the height of the actuator arm.

As I took the plastic cover off the engine the first thing I noticed when I looked at the turbo was that there was a lot of fresh oil and gunky oil around the actuator.20200802_160052.thumb.jpg.e882182b831cb1ba2e0faa243125121e.jpg

Also when I was testing the movement of the actuator connector I noticed that the pipe that runs in front of it was easily moved side ways and that the large Allen key on top was barely hand tight.

So what I have done so far is tighten that Allen key up so the pipe cant move (I'm assuming the oil was coming from there) and have adjusted the screw that stops the actuator from travelling down so that the distance it can move is about half inch...

Took the car for a spin and now it has no power what do ever, I have managed to make it worse. I drove for about 10 minutes to try and make the car throw a code, got back home and plugged the scanner in and nothing, no codes

Anyone have any ideas?

Thanks again

Dread

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Update...

Went back out this morning for a test drive and still no power, 3000 revs only but still no codes. So I decided to go back and re adjust the screw that changes the distance the actuator arm can travel.

First thing I noticed was the connector that the actuator arm goes on was a fair bit stiff this time around until I worked it up and down a few times and it became smooth and free again (possible intermittent sticky vanes?)

Adjusted the screw and put everything back together, went for a drive and the power has returned. I didn't get any warnings or lights and no codes stored.

Do I just continue to use the car as normal until I get fault codes again? Or is it worth stripping the turbo for a clean?

Also I'm still left with a whine/siren noise, in the lower gears where changing gears is quicker, it almost sounds like a police siren and then in the higher gears (motorway) it's just a constant whine.

Thanks

Dread

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Sorry, missed this last night!

Too late now but you shouldn't adjust the actuator arm at all...they're specifically set and calibrated at the factory... :ermm:  

That top pipe is the pressurised oil feed to the turbo.  They often mist a little as they age but yours looks like a bigger leak?  If that's been leaking for a while, the turbo may well be worn from insufficient oil pressure which would also explain the siren noise.

If you want to 'force' an overboost fault, really labour the engine with your foot down in a high gear at speed.  It takes several seconds of overboost to trigger the code so you're generally not in lower gears for long enough before changing up.  

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43 minutes ago, TomsFocus said:

Sorry, missed this last night!

Too late now but you shouldn't adjust the actuator arm at all...they're specifically set and calibrated at the factory... :ermm:  

That top pipe is the pressurised oil feed to the turbo.  They often mist a little as they age but yours looks like a bigger leak?  If that's been leaking for a while, the turbo may well be worn from insufficient oil pressure which would also explain the siren noise.

If you want to 'force' an overboost fault, really labour the engine with your foot down in a high gear at speed.  It takes several seconds of overboost to trigger the code so you're generally not in lower gears for long enough before changing up.  

Won't get any boost with the actuator arm fully tightened though.

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Would a worn turbo from insufficient oil pressure cause the over and underboost? Or is that just the reason for the noise?

I'll take it for a run up the motorway this evening to see of I can force it.

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2 minutes ago, Dread91 said:

Would a worn turbo from insufficient oil pressure cause the over and underboost? Or is that just the reason for the noise?

I'll take it for a run up the motorway this evening to see of I can force it.

Worn turbos can definitely cause underboost, not usually overboost though.  

Overboost can really only be caused by the VNT vanes, either physically sticking or by the boost solenoid not working properly - unless it's the MAP sensor readings that are wrong of course.

Underboost is fairly common from leaks in boost piping, so if you can trigger another overboost, that's a more useful code for us.  It would be best to watch the actual boost figures on a live data graph but appreciate you may need a massive extension cable lol...could you borrow a laptop or OBD dongle for your phone maybe?

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So that whining means I'm going to need a new turbo anyway in the near future?

I will have a phone around to see if there is anyone I can borrow something off but whilst I wait I'll still see of I can get it to throw a code on the motorway once the misses is home.

Also whilst I was having a mess around with the turbo I noticed that the banjo bolt where the leak was coming from had 2 washers above the pipe, is that correct or should one be below the pipe?

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If it's definitely the turbo whining then yeah it won't last forever...I've driven for months on whining turbos though so it's not necessarily an imminent failure.  (Though if it's regularly overboosting, that'll shorten its life) 

One of the copper washers should be below the banjo bolt.  Sounds like your turbo may have already been replaced?  Have you owned the car long?

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I have had it for about 3 years but it has sat for 2 years not being used as it had this overboosting problem and I had another car to use at the time so didn't need to run the two. I used it for about a year and in that time did about 15k (mostly motorway)

I'm no expert but the turbo doesn't look like a factory turbo, I did look around it and couldn't see Garrett anywhere.

Just been out and swapped the washers, one is now below thanks

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If you take the ducting off the inlet side of the Turbo you should be able to put your cleaned fingers in and feel for any play in the bearings.

The bearings do float in oil but you should not be able to feel any play.

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@Tizer

Just done what you suggested and yes there is play in the shaft but we are taking millimetres. Whould that play be causing the whine? If so can it be repaired or is the damaged done?

Thanks

Dread

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A tiny bit of up and down play is normal without any oil pressure.  Shouldn't be any in and out play though.

Feel free to watch probably the most boring video I've ever taken as I was worried about mine 6 years ago...

 

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I agree with Tom about the in and out play, there should not be any. The one in the video has more play than a new one would have but I would not replace it just for that or if it was just whining a bit. Assuming that there were no other symptoms that definitely pointed to a faulty Turbo I would check it regularly and listen for it getting a lot worse.

In the absence of being able to monitor Live Data, probably best to wait for another fault code to appear. From memory I think you can monitor what the Variable Vanes are commanded to do with FORScan but there is no feedback to check that they are doing what they should be.

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Yeah mine has about the same amount of play side to side as that of the video. I didn't feel any play in and out though. Did watch a few videos of whining turbos and mine doesnt sound as bad as most of the ones I saw, so some hopefully promising news.

Didn't manage to take it on the motorway this evening as my closest junction has been closed. But I managed to get hold of a bluetooth obd dongle but it's not a forscan, just one with an app for the phone.

Will do a motorway run tomorrow with it plugged in. What parameters am I looking to log? Anything to do with boost pressure?

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10 hours ago, Dread91 said:

Will do a motorway run tomorrow with it plugged in. What parameters am I looking to log? Anything to do with boost pressure?

There probably won't be many parameters available over OBD2 alone compared to Forscan.  Ideally look for MAP, MAF, torque/load, RPM & MPH.

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