Engine: D5: Low boost pressure & engine service urgent message

[Thassos]

Greetings, i recently had the engine service urgent message pop up along with the Red yellow triangle on the dash...

Some history in this post (not that anyone has replied..)
https://www.volvoforums.org.uk/showthread.php?t=132443

Initially thought maybe it could be VNT/turbo related, although using my simplistic ELM327 OBD2 reader and a few apps like torque there 'appear'
to be no fault codes or impending ones, which is curious as the same apps
have in the past shown engine related codes when there were some..

Anyway today i had a look at the actuator on the turbo (mine has the electronic
module rather than the vaccum variety on some of the earlier cars).. managed to get the circlip off to see if the linkage going into the turbo moved easily and it did with very little resistance, so i guess the electronic
module could be faulty but at least the linkage isnt jammed.

Had a look around for split hoses on the boost side, and couldnt see anything
much, i may try checking the resonator box another day, the engine runs and just doesnt have much power, on the boost side im seeing typ 1-2 psi, with light throttle, and only a max 6-8psi on foot down. Its had a new intercooler not so long ago, and afterward was seeing 18-20psi boost at low revs no problem.

I noticed today the MAF seemed to show 2 readings at tickover, initially (mostly) you see 6.4g/s but saw this change to 14 with no throttle use, on the move it gets to 45g/s max, at 2K type revs, so im wondering if the slightly erratic readings could be a sign of a unreliable MAF? would be useful to know what sort of readings it should be..

Thoughts anyone?

[Sampat1994]

Hey bud mines averages about 15gs but that's cold air intake, I'm also having major issues also having major boost/ fueling issues after head rebuild so don't take mine as necessarily what it should be!! If your still having issues after this weekend could we compare some readings?? Just as I'm away this weekend

What engine ?? Mines d5 and My dad has xc70 d5 and that averages slightly less about 10 I believe but I guess that's down to having air box causing a bit more restriction

[Thassos]

Morning,, thank you for posting, thought this thread had gone dead as surely someone on here has experienced something like what im seeing..

Yesterday (as the fault persists and the engine service urgent message still there, although the yello? mil light has never been lit with this problem.. which is curious) i did a lot of things below, the maf reading at 6g/s def wasnt right, so..

removed intake side/ airbox and Used some maf spray cleaner to give the maf a thorough dosing,

removed the big rubber hose that runs up from intercooler to throttle body inlet, couldnt see much wrong no tears or splits, had a look underneath at the resonator box area and undid the clamps, apart from what looks like a bit of rubber squished out in (will attach some pics) coulnt see much wrong unless ive missed something, the rubber pipe that goes from the hard plastic pipe up to intercooler inlet also looks ok.

Removed the boost pressure / air temp sensor and used some maf cleaner on it, although its readings seem to make sense judging the semi limp performance the engine is giving with max 8psi boost, you can get up to 50 or 60mph but thats about it (easy speed limiter) i then used some egr cleaner spray and cleaner through the throttle body and egr valve area- what a mess, but hopefully may have dislodged any crud perhaps around the egr valve as im wondering if this malfunctions yould loose boost ? as inlet air would bypass the engine inlet?.. running out of ideas to try.. but today im going to discon the vnt linkage and see if moving this (in small steps) will affect the boost, which might lead in the direction of a faulty vnt actuator.. might also swap the fuel filter as its had about 40k miles..

Anyway put it all back together and started up.. felt slightly better .. one noticeable difference was the maf now reading 13g/s at tickover, consistently and slightly higher readings over 50,60 ish at full (8psi) boost on the run, so i think the maf low reading cured, but otherwise very much the same semi limp performance and the error msg persists, it did feel slightly more like it might pick up better but i think its locked into limp mode with its dash message.

Other slightly more difficult ideas.. some sort of exhaust box or cat or dpf blockage thats restricting exhaust flow - .. really could use vida to see if any errors that my elm327 cant see (but all apps i try report no mil and no errors).. anyone got a working vida? i have an old laptop and the dice, that did once run, but is so slow to boot and another repair project in its own right !, i have another old win7 laptop but its home not pro.. arghh more trouble to fix..

[Thassos]

Ild be interested to know (if you have a D5 with the electronic actuator for the vnt turbo.. maybe 2005 onward) if the actuator does anything when you put the ignition on, or before or during startup ?) you can just see it looking down the back of the engine above the turbo, has a flat linkage with a circlip on the top end that goes to the module...

[Simmy]

its not unheard of for the gears in the turbo actuator to fail if sourcing a replacement be careful as i believe there is more than one type. ps have you checked the intercooler for any bowing and or splits/ holes . a smoke test is the best way to test for leaks /problems

[Thassos]

Hi simmy, thanks 4 your reply, well.. i tried removing the turbo actuator, it has a 5 or 6 way connector but only 3 wires are used, tried attaching a flat bar to the linkage to the turbo to manually see what the effect of moving it was on boost pressure, and at tickover or even low revs (1500 rpm ish) it had the effect of moving from vaccum to slight boost (1 and a bit psi at most), i had the actuator plugged in but where i could see it , and it did seem to move small amounts with throttle use, if you try to move the arm it resists movement so it kinda makes me think its doing something.. (but i guess yould have to test its function) so at this point im wondering if it could be egr valve stuck open or just not shutting properly, do you know if you can pressure test the egr valve by applying pressure across the throttle assy while (somehow maybe with vida) to see if it holds pressure when shut ?, def feels like the turbo is not spinning up much if at all..the you really cant see much in the throttle body where the egr valve is without a borescope or similar. yes some pressure testing next on the ideas to try..

[Sampat1994]

Hi mate so in mine , it's down with ignition off, when your turn on the ignition it goes up into a higher position

And so 0% is no boost atall completely open lifted up towards engine. 100% is down to floor max pressure

[Sampat1994]

The 3 wires is one is CAN H one is CAN L and one is power supply and its grounded through the plate its bolted to

[Sampat1994]

Can we talk elsewhere like fb ? So much easier and I can help with pics etc I can't send private message either

[Simmy]

you can view if the egr valve is working by viewing the live data graph go to vehicle communications click on ecm and select egr from the list then select the graph to view egr operation.