boosting hesitant, possible boost control valve?

so ive replaced the maf sensor, and got the turbo boosting great now and put a v band on the turbo, still slight play but not horizontal movement so itll do, but ive still got this annoying hesitation when boosting? it happens mainly at 3 stages, boost coming on (3k ish) low mid (4k ish) and mid boost (5k ish) after 5k it boosts great to 6500. sometimes it does longer period of times. theres no fault codes, as said new maf, which leaves me to believe its the boost valve? this is where i get the slight "beep" noise from the passenger side (coincidentally the boost control valve is there?) sound plausible?
thanks guys :)

petrol diesel. what year model. have you read the codes thats the first place you need to start.

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Originally Posted by s40t

so ive replaced the maf sensor, and got the turbo boosting great now and put a v band on the turbo, still slight play but not horizontal movement so itll do, but ive still got this annoying hesitation when boosting? it happens mainly at 3 stages, boost coming on (3k ish) low mid (4k ish) and mid boost (5k ish) after 5k it boosts great to 6500. sometimes it does longer period of times. theres no fault codes, as said new maf, which leaves me to believe its the boost valve? this is where i get the slight "beep" noise from the passenger side (coincidentally the boost control valve is there?) sound plausible?
thanks guys :)

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If your T4 then these are really fussy motors....you won`t get full boost properly unless the temp guage says 88C but 92C is the correct running temp.

It is a failsafe measure for any damage to the engine.......so i would check that first then move on...... check the TCV is ok by removing a hose from it either red or yellow but be careful as it will boost wildly if all the rest is ok!!

It never done it when I got the car but a day and half later it started. Would it be more be beneficial to have a manual valve than the electronic?

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Originally Posted by 960kg

If your T4 then these are really fussy motors....you won`t get full boost properly unless the temp guage says 88C but 92C is the correct running temp.

It is a failsafe measure for any damage to the engine.......so i would check that first then move on...... check the TCV is ok by removing a hose from it either red or yellow but be careful as it will boost wildly if all the rest is ok!!

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I'll try this, thanks

I would check all of your hoses first. Do the things that cost no money first

thanks weemo, a little update on the problem. i have installed a boost gauge, and when it is hesitating, theres NO boost loss, i think this means i can rule out any split pipe, vaccums etc. ( i have already checked multiple times anyway.)

ive also noticed more and more often now, when on idle mainy warm up the rev hunt every now and then? its NOT the maf, no fault codes and its brand new. cant imagine another sensor as its started doing with this new maf so...
in my theory (bare with me!) i can only put it down to either this tcv or FP, im edging more fp now from the boost gauge, maybe not coping with the demands when theres a change in revs, having to build the pressure up, maf is now reading the correct amount of air drawn in, FP cant cope causing hesitation. fuel pressure build eventually in fuel line/ rail over the period of hesitation, hence it not hesitating over 4.5-5k? lack of pressure on fuel, not as much fuel supplied, tcv notices this possible reason of this "beep"...does it sound plausable? i still need to disconnect them lines, ill try tomorrow as been busy, if no change i can only say fuel pump is giving in.

Ive got a similar issue on a T3 engined V40 (2003) but mine only apparent when accelerating from <2k, sometimes it will hesitate 2-3 times but once over 2k it acts fine. but my boost seems low seeing peaks of 10psi on initial acceleration which then drops to 4-5psi, but no leaks and car accelerates well.

I keep getting P0171 code which comes and goes but plug reading shows nothing amiss, strange thing is when i check the freeze frame for the code the engine temp is always 84c. Engine is heating up to 88-92 just fine.

Update on this.

Replaced FPR, engine ran a lot better, hestitations less noticable. Old FPR was 309Kpa, New one is a 350Kpa. Getting full pressure at the rail. Annoyingly P0171 sat as a pending fault but no light....

Replaced MAF, P0171 gone, I did have a grey code for P0234 overboost after the MAF change but that has now gone as well, but getting what feels like fuel cut/limiter kicking it at 3k with random hesitations. No faults logged or pending :-/

I have got new coils to go in this afternoon so will see if that makes a difference.

Whats the fpr

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Originally Posted by Cymro

Ive got a similar issue on a T3 engined V40 (2003) but mine only apparent when accelerating from <2k, sometimes it will hesitate 2-3 times but once over 2k it acts fine. but my boost seems low seeing peaks of 10psi on initial acceleration which then drops to 4-5psi, but no leaks and car accelerates well.

I keep getting P0171 code which comes and goes but plug reading shows nothing amiss, strange thing is when i check the freeze frame for the code the engine temp is always 84c. Engine is heating up to 88-92 just fine.

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Standard boost on your motor is only 8.7psi as it is a weaker engine!........you can only safely boost to 12psi continuously otherwise can be a nasty bang!.......it does sound as though your TCV may need replacing as on initial acceleration you should not see 10psi...

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Originally Posted by Cymro

Update on this.

Replaced FPR, engine ran a lot better, hestitations less noticable. Old FPR was 309Kpa, New one is a 350Kpa. Getting full pressure at the rail. Annoyingly P0171 sat as a pending fault but no light....

Replaced MAF, P0171 gone, I did have a grey code for P0234 overboost after the MAF change but that has now gone as well, but getting what feels like fuel cut/limiter kicking it at 3k with random hesitations. No faults logged or pending :-/

I have got new coils to go in this afternoon so will see if that makes a difference.

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I said on the other site that the MAF will probably be the cause of the P0171 error code but over there you don`t say it worked!!

If you say you still have a misfire then replace the front O2 sensor as that is one of the causes of the code according to Vadis and not the MAF as usually is found out in practice.....

The 171 has now gone. After the MAF change.

It now doesn't feel like a misfire. More as if im hitting a limiter or boost cut off.

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Originally Posted by Cymro

The 171 has now gone. After the MAF change.

It now doesn't feel like a misfire. More as if im hitting a limiter or boost cut off.

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@960kg, changed my coil packs and it feels like new :-)

I think there may have been more than one issue at work and replacing everything else made the misfire stand out more and more.

Thanks for the help

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Originally Posted by Cymro

The 171 has now gone. After the MAF change.

It now doesn't feel like a misfire. More as if im hitting a limiter or boost cut off.

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I am pleased the error code has gone.....owners can actually hang on this code for a year trying to erase it but in the end the MAF has a 99% chance of getting rid of it ....why? ...who knows, but there are countless posts around to prove it.

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Originally Posted by Cymro

@960kg, changed my coil packs and it feels like new :-)

I think there may have been more than one issue at work and replacing everything else made the misfire stand out more and more.

Thanks for the help

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As you say, more than one issue at work......it is always best to try and fit pucker Volvo parts with turbos as they are so fussy.....aftermarket parts cost more in the long run ( well..... after 6 months when you have to buy them again! )

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Whats the fpr

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Originally Posted by abdul

Whats the fpr

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Fuel pressure regulator located on the end of your fuel rail at the front of the engine

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Originally Posted by gazO2V40T4

Fuel pressure regulator located on the end of your fuel rail at the front of the engine

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Thanks