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V70R Overboosting/Knocking/Lack of power

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

NewKidOnTheBlock
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V70R Overboosting/Knocking/Lack of power

Post by NewKidOnTheBlock » Wed Apr 15, 2020 10:06 am

I've got an issue with my 1998 V70r where if I go full throttle (or most throttle) I get a juddering and lack of power at around 3k RPM. The car's been like this for ages (possibly my entire ownership) but I've always driven around it and backed off the throttle when this occurred. I always run it on premium fuel as I'm sure it's worse on regular.

Years ago I replaced the Turbo Control Valve with an IPD HD TCV and all vacuum lines too (maybe relevant?)

Today I decided I would finally get around to checking the waste gate actuator, I've now set this to 4.4PSI to open, previously it was wound so long that it was barely even holding the gate closed with no pressure. (There was no clip either so I guess someone's played with this before).

After setting the waste gate actuator, hoping this would have cured all of my woes I found there was no change! So I fitted a cheap boost gauge that I had kicking about, this shows that when I reach 3,000RPM I seem to go up to about 14PSI and this is when the knocking/juddering begins, naturally I let off the throttle to stop this so I don't know if the car drops boost or that's just me closing the throttle.

I wonder if I need to re-teach the TCV after looking back in the manual but don't know if this would cause this? Any other ideas? Maybe my car's been badly remapped in the past?

Thanks in advance.

J.

NewKidOnTheBlock
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Re: V70R Overboosting/Knocking/Lack of power

Post by NewKidOnTheBlock » Wed Apr 15, 2020 10:08 am

Oh, I should also add that my car's an auto so I believe it comes with a lesser turbo and lower boost pressure than the manual equivalent.

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Re: V70R Overboosting/Knocking/Lack of power

Post by NewKidOnTheBlock » Thu Apr 16, 2020 8:36 am

Right... no responses as yet but I've spent the day working on it and have found a few things... After reading most posts I could find ref over boosting or similar issues I noted that most were down to vacuum issues. So I started by checking all vacuum hoses and connections were good, I found that I must have replaced the 3 for the TCV when I did that a while ago so they're nice thick silicone ones. I found that the hose that goes from the front of the manifold infront of the tree over to the to of the turbo was manky, I don't think it was split but I replaced it anyway. The main culprit however - the TCV seems to have had 2 hoses transposed (oops) so the waste gate actuator and the intake snorkel hoses were the wrong way around, obviously I put this right.

While I was there I also cleaned out the IAC valve as this looked pretty heavily caked in grime, some blasting with throttle cleaner and a small brush and that looks much better.

I had disconnected the battery while doing all of this and decided to try and get the ECU to relearn the TCV as per the instructions, warm up engine, do a half boost pull for 5-7 seconds, slow to sub 30mph and repeat 4 times, turn off ignition and wait for 12 mins, repeat.

I then tested the car and overall I would say it felt much better but still had a cutout issue and seemed to over boost.

Many misfire issues also seem to be attributed to plugs so I decided to replace these, I got some Bosch Super Plus copper ones, checked all were gapped at 0.7mm and installed.

Test drive again and it still seems to have the issue, I can now go full throttle for a sustained amount of time which I couldn't do in the beginning but still get cutouts when pulling hard. this time I noticed that I still seem to hit 13-14PSI after a sustained pull and then it cuts. I don't know why this is happening as far as I can tell everything it set correctly and everything seems to work, my only thoughts on the matter are - dodgey remap? or perhaps the waste gate actuator isn't working properly, not opening fast enough perhaps?

scot850
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Re: V70R Overboosting/Knocking/Lack of power

Post by scot850 » Thu Apr 16, 2020 11:49 am

Do you have a stock TCV? They can become sticky with age. The standard unit is only rated to 12 psi, so boosting beyond there may be causing issues and vice versa. I doubt you have an IPD TCV which can boost higher for tuned engines, but they have an issue when installing then that can cause sticking valve in the TCV.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

NewKidOnTheBlock
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Re: V70R Overboosting/Knocking/Lack of power

Post by NewKidOnTheBlock » Thu Apr 16, 2020 12:59 pm

Hi Neil,

Thanks for the reply, I do have an IPD TVC fitted, are you saying those can also stick? Perhaps it's worth blasting it through with throttle/carb cleaner or is that likely to damage it?

Jamie

scot850
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Re: V70R Overboosting/Knocking/Lack of power

Post by scot850 » Thu Apr 16, 2020 1:22 pm

Is your IPD TCV one with the 3 plastic 'spider legs'? If so the issue with those is the 'middle' leg on the front of the unit. Despite me flagging the issue with this to IPD they have never fixed their install instruction. This middle leg should be screwed on by no more than 3-4 rotations. Yes it will feel loose, but the problem with screwing all the way in is that there is a small wire mesh filter inside the hole. If you screw the middle leg all the way in it crushes the mesh against the valve making it either non-operational or sticky in operation. If you can get your hands on an original used version you may find this fixes the issue. The IPD version is not needed on the stock tune on an 'R'.


I have the IPD TCV and they supplied me with a free replacement as I pointed out that the issue was not mine but theirs and the fact was made worse as they knew of the issue but did nothing about it.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

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Clemens
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Re: V70R Overboosting/Knocking/Lack of power

Post by Clemens » Thu Apr 16, 2020 1:59 pm

Maybe try reducing the length of the wastegate actuator rod and see if that helps.
Also, my overboosting/fuel cutout issues were just caused by bad ignition components. I had OE Bosch cap and rotor fail within 3 years.
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

NewKidOnTheBlock
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Re: V70R Overboosting/Knocking/Lack of power

Post by NewKidOnTheBlock » Thu Apr 16, 2020 2:55 pm

Hi Guys,

Thanks for the responses.

Neil - Yes my IPD TCV is the one with the "spider leg" right angle joints, I did come across you mentioning the over tightening issue in another thread last night actually, I did check when I was in there earlier and noticed that all of the elbows were threaded in but loose to turn. I don't think I would have wound them in tight then back out when installing but it's not an impossibility.

Clemens - I did wonder about using the rod length adjustment to reduce boost but I thought it would be the other way, if I lengthen the rod then surely it's going to actuate sooner so reduce power? Although again from what I've read surely this will change it's initial response but not make much difference to the peak boost?

Regarding the fuel cutout - I've been thinking about this, how does the ECU know when to do this? I didn't think these early engines had a boost pressure sensor so what's giving the signal that boost is exceeding the limit? Is there a way to bypass the fuel cutout or perhaps disable it temporarily so I can find out if that's really happening? I did wonder if I could run a gauge to the fuel rail so I can monitor rail pressure while doing a pull to see if rail pressure drops off, otherwise it would be interesting to monitor. Any ideas?

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Clemens
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Re: V70R Overboosting/Knocking/Lack of power

Post by Clemens » Thu Apr 16, 2020 3:04 pm

I'm super tired after a 3 hour MTB tour today, so my brain isn't functuonong properly.
Please lengthen it, shortening will just bring boost buildup earlier.
Yes, the overall boost should remain the same, but if it comes later the ECU might be okay with it.
Do you know if someone tinkered with the tune in the past?
Summer: 1996 855 R
Winter: 1994 855 T5M
Donor: 1995 854 10V

scot850
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Re: V70R Overboosting/Knocking/Lack of power

Post by scot850 » Thu Apr 16, 2020 3:05 pm

Remove the middle leg and check the small wire filter for damage. If I recall it should be a little domed and of uniform appearance. If not it is damaged. It may be possible to pull the filter out to see if that will help.

Not sure of a fuel cut out, but others may be aware of one.

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

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