Coming on and off boost?

[Tee5alive]

put over 3000 miles on the car since the rebuild (new turbo, alternator etc) and initially this problem was small. But gradually this is getting more pronounced. Even trying TOP GRADE 'super' petrol its happening.

Under hard acceleration the car boosts hard then backs off, then boost/back off etc ??? I have replaced the ETM body and this was initially suspect to no avail. It is getting VERY pronounced and boost is kicking in with a vengeance at times almost putting me through the drivers seat, wheels spinning etc (even at motorway speeds) - THEN drops to nothing?

I am getting an intermittent ENGINE SYSTEM SERVICE due and now and then BRAKE ASSIST SYSTEM SERVICE. Which knocks out CRUISE control.

Is this possibly simply an air leak somewhere as now and then the turbo sounds a little LOUD in the car. The car otherwise is fine, just a bit embarrassing when peak acceleration is called for!

ideas please??

[S70T5Chris]

Tcv?

[Soulboy]

I had this same problem and only got to the bottom of it last week, turned out to be the map sensor

With that replaced it boosts the same all the time, everytime

However, if you wanna try the tcv first, I have a spare here that I bought while chasing the fault that you are welcome to try (-:

[Biff]

Map, Maf or tcv/bcs.

[Tee5alive]

I had this same problem and only got to the bottom of it last week, turned out to be the map sensor

With that replaced it boosts the same all the time, everytime

However, if you wanna try the tcv first, I have a spare here that I bought while chasing the fault that you are welcome to try (-:

thanks Soulboy, on my next pitstop when I can do some work on her I'll give that a try - ill be in touch!

[Soulboy]

thanks Soulboy, on my next pitstop when I can do some work on her I'll give that a try - ill be in touch!

No worries mate,pm me your address and I'll send it to you!

[Shinsplintz 101]

I don't want to muddy the water..... BUT... my old mans old late P1 T5 had a similar problem & it was the ABS module. Threw up weird engine warning lights, codes & intermittent boosting issues [probably due to the ECU ££££ting itself with the codes]. Don't know if the P2's suffer with the same dodgy ABS modules, but thought I'd throw it out there...good luck

[expolicev70t5]

Got same issue on mine, then I get an over boost code and boost cut. I've got it down to be TCV that's faulty.

[Tee5alive]

I don't want to muddy the water..... BUT... my old mans old late P1 T5 had a similar problem & it was the ABS module. Threw up weird engine warning lights, codes & intermittent boosting issues [probably due to the ECU ££££ting itself with the codes]. Don't know if the P2's suffer with the same dodgy ABS modules, but thought I'd throw it out there...good luck

INTERESTING as I start off with no codes then an ENGINE SERVICE on the DIM and then BRAKE ASSIST advisory - hmmmm thats interesting. Thank you all

[Orca2]

Could be cracked abs rings, they open up when you boot it , the abs sensors then see the crack and cut your power cos they assume you are skidding, mine used to do it on roundabouts new rings cured it. The abs fault was dumping all the boost .

[Mart5in]

INTERESTING as I start off with no codes then an ENGINE SERVICE on the DIM and then BRAKE ASSIST advisory - hmmmm thats interesting. Thank you all

The brakes don't feel heavy at any point do they? Might be worth checking the pipe that goes from the manifold to the brake servo. It's got a little one-way valve on it.

As far as I know (what my local Volvo dealer told me) the P2 don't suffer from the same ABS module faults as the P1 did. all the P2's normally fail on the front sensors and rings. Rarely the rear sensors.

When you changed the ETM, did you fit one from another Volvo and have it coded? Or did you have it repaired with the contactless tps?

[Tee5alive]

The brakes don't feel heavy at any point do they? Might be worth checking the pipe that goes from the manifold to the brake servo. It's got a little one-way valve on it.

As far as I know (what my local Volvo dealer told me) the P2 don't suffer from the same ABS module faults as the P1 did. all the P2's normally fail on the front sensors and rings. Rarely the rear sensors.

When you changed the ETM, did you fit one from another Volvo and have it coded? Or did you have it repaired with the contactless tps?

NO Martin just bought a used ETM fitted it , disconnected battery to reset and that was it, BUT still hunting a little on idle

ORCA - THAT is interesting about the rings will check it thanks all

[Harvey]

NO Martin just bought a used ETM fitted it , disconnected battery to reset and that was it, BUT still hunting a little on idle

ORCA - THAT is interesting about the rings will check it thanks all

Next time you're down south give me a shout & I can stick my code reader on it .

[LeeT5]

Another dead thread with no result and no response.

[Mart5in]

Well, I know I'm not op but my situation was VERY similar and a new MAF combined with the ETM repair fixed it

all I've got left is a misfire from cold under load. can't set off without letting the engine run for a few mins.

[LeeT5]

Well, I know I'm not op but my situation was VERY similar and a new MAF combined with the ETM repair fixed it

all I've got left is a misfire from cold under load. can't set off without letting the engine run for a few mins.

Have you changed your plugs? Fit Genuine.

[Mart5in]

Yeah, I did change the plugs. Not Volvo, I used ngk but theyre the same heat rating if I remember correctly. I can't remember if the problem was there before I changed the plugs. I'll try the old genuine plugs back in sometime this week.