850 T5R momentary cut out under hard acceleration

PSJVTHEBEST · Apr 25th, 2024, 10:50

Dancake has kindly sent me a TCV to try but I have a poorly dog here at the moment who is taking up all my time so please don't think I have left this thread hanging. I will definitely fit it as soon as I can and revert. Thanks to Baffler and Luxobarge for their latest contributions.

PSJVTHEBEST · May 10th, 2024, 18:46

An update!
I switched over to the TCV kindly supplied by Dancake and there seemed to be an improvement in so far as the cutting out was less prevalent and at higher revs. But still there!
I am going to look at the turbo actuator now to see if it is sticking. I can get a hand to it and move it c. 10mm but don't know if that is enough to suggest it's ok. I will be able to get to it better once I have removed the heat shield.
I am still running with the non-Bosch replacement MAF sensor and am wondering if that might be contributing to the problem in some way e.g. unable to cope with the overboost?
I will update once I have got to grips with the actuator.

Luxobarge · May 10th, 2024, 19:37

I believe I'm right in saying that these cars are indeed quite picky about the quality and exact specification of MAF, and general opinion is that only original Bosch MAF is good enough, so if it were me I'd definitely be replacing that with a proper Bosch one of the correct part number, expensive though it might be.

PSJVTHEBEST · May 10th, 2024, 19:48

Thanks Luxobarge. yes, I have heard and read that too. Being somewhat, let's be generous to me, careful with money, I have wanted to exhaust other, possibly cheaper, potential solutions before buying a Bosch one. Especially since it's not throwing up any MAF related fault codes.

nickm · May 11th, 2024, 05:03

What plugs are you running?

Also I had this with a bad coil pack
And if the cam timing is off

PSJVTHEBEST · May 15th, 2024, 10:01

Genuine Volvo spark plugs.
I have put on a new camshaft position sensor which I hope reduces the risk of the cam timing being off but still could be, I guess.
I haven't investigated the coil yet-maybe underperforming under load perhaps?
Thanks for your comments.

Baffler · May 11th, 2024, 13:22

Quote:

Originally Posted by PSJVTHEBEST

An update!
I switched over to the TCV kindly supplied by Dancake and there seemed to be an improvement in so far as the cutting out was less prevalent and at higher revs. But still there!

But isn't this the whole reason why Dancake swapped out his old TCV for a new one? I would still try an new TCV if only to eliminate it from the equation.

Yes, it would seem most Volvo engine management systems are sensitive to having the correct MAF meter and aftermarket can cause a host of running and performance issues.

PSJVTHEBEST · May 15th, 2024, 10:02

It was from another car that had no issues, Liam. Agreed though, the absolute best option is a new one!
The old MAF will be going back in!
Thanks for replying.

Dancake · May 15th, 2024, 10:29

Quote:

Originally Posted by Baffler

But isn't this the whole reason why Dancake swapped out his old TCV for a new one? I would still try an new TCV if only to eliminate it from the equation.

Yes, it would seem most Volvo engine management systems are sensitive to having the correct MAF meter and aftermarket can cause a host of running and performance issues.

The TCV I sent came from another 850 and I never tested it. I did replace my original with a Pierburg unit but the one that came out was tested as faulty.

May 10th, 2024, 19:37	#3
Luxobarge Premier Member Last Online: Today 10:04 Join Date: Jan 2011 Location: Horne (Nr. Horley)	I believe I'm right in saying that these cars are indeed quite picky about the quality and exact specification of MAF, and general opinion is that only original Bosch MAF is good enough, so if it were me I'd definitely be replacing that with a proper Bosch one of the correct part number, expensive though it might be. __________________ Some people are like Slinkies, they serve no useful purpose but they still bring a smile to your face when you push them downstairs.

Apr 25th, 2024, 10:50	#1
PSJVTHEBEST VOC Member Last Online: May 15th, 2024 10:02 Join Date: Dec 2002 Location: Tiverton	Dancake has kindly sent me a TCV to try but I have a poorly dog here at the moment who is taking up all my time so please don't think I have left this thread hanging. I will definitely fit it as soon as I can and revert. Thanks to Baffler and Luxobarge for their latest contributions.

May 10th, 2024, 18:46	#2
PSJVTHEBEST VOC Member Last Online: May 15th, 2024 10:02 Join Date: Dec 2002 Location: Tiverton	An update! I switched over to the TCV kindly supplied by Dancake and there seemed to be an improvement in so far as the cutting out was less prevalent and at higher revs. But still there! I am going to look at the turbo actuator now to see if it is sticking. I can get a hand to it and move it c. 10mm but don't know if that is enough to suggest it's ok. I will be able to get to it better once I have removed the heat shield. I am still running with the non-Bosch replacement MAF sensor and am wondering if that might be contributing to the problem in some way e.g. unable to cope with the overboost? I will update once I have got to grips with the actuator.

May 10th, 2024, 19:48	#4
PSJVTHEBEST VOC Member Last Online: May 15th, 2024 10:02 Join Date: Dec 2002 Location: Tiverton	Thanks Luxobarge. yes, I have heard and read that too. Being somewhat, let's be generous to me, careful with money, I have wanted to exhaust other, possibly cheaper, potential solutions before buying a Bosch one. Especially since it's not throwing up any MAF related fault codes.

May 11th, 2024, 05:03	#5
nickm Member Last Online: May 14th, 2024 14:48 Join Date: Oct 2008 Location: Sydney Australia	What plugs are you running? Also I had this with a bad coil pack And if the cam timing is off

May 15th, 2024, 10:01	#6
PSJVTHEBEST VOC Member Last Online: May 15th, 2024 10:02 Join Date: Dec 2002 Location: Tiverton	Genuine Volvo spark plugs. I have put on a new camshaft position sensor which I hope reduces the risk of the cam timing being off but still could be, I guess. I haven't investigated the coil yet-maybe underperforming under load perhaps? Thanks for your comments.

May 15th, 2024, 10:02	#8
PSJVTHEBEST VOC Member Last Online: May 15th, 2024 10:02 Join Date: Dec 2002 Location: Tiverton	It was from another car that had no issues, Liam. Agreed though, the absolute best option is a new one! The old MAF will be going back in! Thanks for replying.

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