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'98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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abscate
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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by abscate » Mon Mar 12, 2018 3:47 am

Your turbo won't have the heated air intake as the inter cooler regulates intake air temperature

With the MAF disconnected the ECM will run on a table of values generated by rpm, which explains why that's will run well. Perhaps the Idle air control valve will let air in during your tests!


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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by SvenGWK » Mon Mar 12, 2018 11:16 am

Thanks for your answer.
If I understand the meaning of the idle control valve correctly, it ensures that the engine runs even when the throttle valve is closed by creating a bypass for the air.
That air would have to be sucked in through the intake hose, wouldn't it?
The problem is, the engine runs as normal when I close the intake hose with my hand, no air is sucked in from there.
When the car was parked overnight, it takes air through the intake hose, but only for a short time.
I don't understand where the engine gets the air.
I think there are not so much more opportunities to suck false air after the throttle valve?

Unfortunately, it's raining like hell again. I wanted to spray the throttle valve and intake manifold again with a brake cleaner, hoping to find a leak somewhere. I don't have a covered garage. :-/



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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by sleddriver » Mon Mar 12, 2018 12:40 pm

This is very odd as air is needed for combustion. Further, from what you've said, unmetered air is entering downstream of the MAF. That's not good as the ECM can't account for it.


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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by abscate » Mon Mar 12, 2018 2:26 pm

sleddriver wrote:
Mon Mar 12, 2018 12:40 pm
This is very odd as air is needed for combustion. Further, from what you've said, unmetered air is entering downstream of the MAF. That's not good as the ECM can't account for it.
Unless you unplug the MAF, in which case the ECM guesses, and its usually pretty close.

:D


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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by SvenGWK » Tue Mar 13, 2018 12:07 pm

Would it be a possibility that the engine could suck the air from the exhaust system through the turbocharger?
The wastegate somehow makes me wonder.
The push rod doesn't move at all, I touched it and let the engine turn up - nothing.
There is a slight vibration on the rod when trying to pull it towards the turbo.
The rod is completely immobile when the engine is really cold, and has minimal room for movement when the engine is warm.
Unfortunately, I don't know the normal condition of the Volvo, but as I have seen in various videos of other vehicles, the rod can be moved and even move when the engine is accelerating.
As i know, a permanently closed wastegate would provide a lot of pressure and power (at least for a while...).
At the moment, however, the car doesn't seem very powerful to me...

Actually, the hose has been found detached from the intercooler a long time ago, there was always a hissing noise when switching gears and the car did not accelerate properly.
I've been told, the cause was a rusted hose clamp.



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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by scot850 » Tue Mar 13, 2018 1:12 pm

The turbo bypass valve has a rubber diaphragm in it. You also have a TCV (turbo control valve) on a turbo engine. Both can and do fail with age. There is a small rubber pipe that runs from the TCV (usually mounted on the side of the airbox near the MAF. One of the small pipe runs down to the TBV. Remove that pipe at the TCV and pull a vacuum on the pipe to see if the TBV holds a vacuum. If it doesn't that may explain the lack of movement and power to the engine. If it does work it could be the TCV has failed.

Neil.
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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by SvenGWK » Tue Mar 13, 2018 1:52 pm

Thanks for your answer.
The TCV was replaced 2 years ago. At that time I had simply bought all the parts that seemed to make sense to me (because of the error that finally turned out to be a broken line at the intercooler). An original part made by Pierburg was used. What really worries me is that I can't move the wastegate pushrod by hand. I know that in the actuator the retraction is realized with a spring, but is it really so strong that the rod cannot be moved manually?



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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by abscate » Tue Mar 13, 2018 7:06 pm

It should move by hand easily. It sounds frozen up


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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by scot850 » Wed Mar 14, 2018 8:27 am

Agreed.

Neil.


2000 V70 R - still being an endless PITA
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Re: '98 Volvo C70 2.5T atmospheric pressure sensor and high consumption

Post by SvenGWK » Sun Mar 18, 2018 6:07 am

...After days of trying and guessing, I have discovered the root of all evil.
I built a smoking machine and have blown the smoke into the hose that leads from the compressor housing to the TCV.
I had suspected this hose anyway, because there is no pressure there - that's why the Wastegate doesn't work either. The smoke exits directly at the clamp, I suspect it has either not been tightened or the hose has ruptured/burst there.
Maybe a marten gnawed on it, I had fur remains on the engine every now and then and at the insulation of the bonnet also once one had fun.
Now, however, I have the problem that this part is almost inaccessible for me.
Is it possible to replace the hose (and tighten the clamp!) without removing the turbocharger?

Smoking machine in action:
http://sendvid.com/9m42jxba



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