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On-going boost issues

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

Mstrshkbrnnn
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On-going boost issues

Post by Mstrshkbrnnn » Sat Mar 28, 2020 6:37 pm

I've had this '96 R for a while now and since I've gotten it, I've had random boost issues. First, the car hardly boosted at all. I smoke tested the intake system and found a crack in my intercooler, and on the turbo inlet pipe. Swapped in an intercooler from a dead s70 glt, and put in an ipd silicone intake pipe. I kept the stock airbox. After replacing that, the car would boost very quickly, but would then cut spark and rev limit at around 4k. I then replaced the tcv lines and found that the vacuum line running from the compressor housing was broken. I replaced the spark plugs, and that took care of the cutting issue, it would now pull to redline, but would feel a bit slow for "240" hp. I decided to stop wasting my time with the "boost gauge" that comes stock in the car, and bought a "temporary" harbor freight boost gauge (I really want the IPD one but am waiting until more pressing issues are resolved before spending that much on something for appearance). Boost gauge reads a slow climb to 5 psi before stopping there. I thought maybe the cbv was torn since I was experiencing symptoms of a torn one so I bought the upgraded ipd one but kept the stock spring. I replaced the vacuum line for the cbv as well. Nothing. The car still felt slow. I decided to try unplugging the red vacuum line going to the tcv (the compressor housing line), and to my surprise the car hauled ass. It spike at around 15 psi and maintained around 12-13 and the car felt great. I figured the tcv was bad due to oil getting in it (the originally line broke due to being soaked in oil). Just today I installed the upgraded pierburg tcv 7.22908.03.0 and I thought today would be the day it boosts normally. After installation I started the car with the appropriate lines connected, and drove the car. 5 psi. I drove back home then remembered since I had one vacuum line disconnected, I probably threw a MAF code. I checked and sure enough there was a MAF code. I erased it thinking "This is it!" It wasn't. I'm still peaking at only 5 psi, and the climb to it is very slow. Whats going on here??
'94 854 NA 287k (bought for $400)
'98 s70 GLT 243k (bought for $250 currently non running)
'96 854R 173K (bought for $900)
'88 245 DL who knows (bought for $600)

Sommerfeldt
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Re: On-going boost issues

Post by Sommerfeldt » Sun Mar 29, 2020 3:28 pm

Hey!

Okay, so boost control is pretty straight forward, and it can still be an absolute PITA to untangle when it goes "wrong". :)

The first point of order, as it were, should be to reset the ECU, to make sure there are no codes making it dial back the boost. If you do a reset (ie pull the battery a couple of minutes) go for a drive and the boost comes on normally, it's solved. If it comes on normally, only to drop off again, there's a code somewhere, or something is malfunctioning, making the ECU cut the boost.

If nothing changes, then we move on. You said that you get normal boost levels if you rob the ECU of control. So pipes, IC and compressor are all in order. This kind of narrows things down.

- Check your TCV hoses. Thrice. Make sure you are following the correct diagrams - there's at least one floating around with the wrong order of things.
- Check your WG actuator. It could be broken/leaking, or not set correctly at all. There's been several people with low boost issues, where the rod was simply set to where the WG would open just by looking hard at it, so to speak. Ideally, get a low pressure gauge, a check valve, a t-split, some hoses and a bicycle pump, and set it according to specs for your car. It's not hard (I managed to build a tool and do it, so it can't be hard.)

Since even the climb to 5psi is slow, it makes me think the WG is opening immediately... but go through the list anyway. :)

- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

Mstrshkbrnnn
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Re: On-going boost issues

Post by Mstrshkbrnnn » Sun Mar 29, 2020 4:09 pm

You know that makes sense. I’m thinking it’s a waste hate issue too, because under WOT, if you listen closely (which is hard to do since the car has no muffle right now and is flowing straight out of the cat), you can hear what sounds like a wastegate opening and closing at the speed of light. It’s a super fast like vibrating noise coming from the turbo that I assumed to be the waste gate opening and closing super fast. Could the wastegate itself be ruined? Could you explain a little better how exactly to test it? Also all my turbo-related vacuum lines are new silicone, and I’ve spent the last 8 months reading and messing w them. They’re not in the wrong places, and they aren’t torn.
'94 854 NA 287k (bought for $400)
'98 s70 GLT 243k (bought for $250 currently non running)
'96 854R 173K (bought for $900)
'88 245 DL who knows (bought for $600)

Sommerfeldt
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Sommerfeldt

Re: On-going boost issues

Post by Sommerfeldt » Sun Mar 29, 2020 5:58 pm

Since you could boost to 15/12-13psi without actuator control, there's probably nothing wrong with your wastegate itself, but it sounds to me that the actuator is doing strange things. Also, you should definitely not be hearing it under any circumstances, really.

What I mean by checking the lines, is check that the TCV lines are in the correct locations. If the WG actuator one is switched with another, you might get these symptoms. BUT - check or replace your wastegate actuator. If it's original, it's overdue - the heat cycles will kill it eventually. However, you should see if you can set it to the correct pressures first, and see what happens. Use a tool that lets you see the pressure you're setting it at - buy, rent, borrow or make one, and do it the right way. :)

Testing it is pretty easy.
Hose with check valve from a bike pump to a T-fitting. Low pressure meter on the fork of the T-fitting, and hose onwards to the WG actuator. Use the bike pump to put pressure on the line (which will be held in the line by the check valve), and see if the WG actuator holds pressure (don't go crazy). If it does, set the WG opening pressure to spec - I can't recall what it is for your car right now, but a quick search here should do it. :)

- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

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Re: On-going boost issues

Post by Sommerfeldt » Sun Mar 29, 2020 6:07 pm

Here's what you make (sorry about the iPhone edits - I had to repurpose the check valve and hose a while ago):
88A141F0-D2BE-4CBC-BC42-497990474F6B.jpg
- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

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Re: On-going boost issues

Post by abscate » Mon Mar 30, 2020 6:57 am

One note - you can't get an accurate waste gate setting with a 100 psi gauge on the low end of the scale - and the cheaper the gauge, the worse it will be

The set pressure for locating the waste gate is something like 3-5 psi depending on model/year - the error on a 100 psi gauge can be twice that.
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Sommerfeldt
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Re: On-going boost issues

Post by Sommerfeldt » Mon Mar 30, 2020 10:32 am

abscate wrote:
Mon Mar 30, 2020 6:57 am
One note - you can't get an accurate waste gate setting with a 100 psi gauge on the low end of the scale - and the cheaper the gauge, the worse it will be

The set pressure for locating the waste gate is something like 3-5 psi depending on model/year - the error on a 100 psi gauge can be twice that.
Exactly right.

Get a low pressure gauge like in the picture - 1 bar/15 psi max works well for this kind of thing. :)

- S
'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

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Re: On-going boost issues

Post by Clemens » Thu Apr 02, 2020 12:17 am

Maybe I didn't see it, but sid someone suggest the diaphragm in the CBV? I had a tiny hole in it, and it made boost bounce around and generally low. Also, I heard a hissing noise getting off boost while it was there.
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Mstrshkbrnnn
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Re: On-going boost issues

Post by Mstrshkbrnnn » Wed Apr 15, 2020 7:03 pm

Clemens wrote:
Thu Apr 02, 2020 12:17 am
Maybe I didn't see it, but sid someone suggest the diaphragm in the CBV? I had a tiny hole in it, and it made boost bounce around and generally low. Also, I heard a hissing noise getting off boost while it was there.
upgraded that part longggggg ago. just got back home to the PNW from attending a funeral in NY. Hopefully I'll be able to purchase those items to test my WG actuators a timely manner.
'94 854 NA 287k (bought for $400)
'98 s70 GLT 243k (bought for $250 currently non running)
'96 854R 173K (bought for $900)
'88 245 DL who knows (bought for $600)

Mstrshkbrnnn
Posts: 41
Joined: Wed Jul 10, 2019 12:13 am
Year and Model: 94 850
Location: Seattle
Has thanked: 4 times
Been thanked: 2 times
United States of America
Mstrshkbrnnn

Re: On-going boost issues

Post by Mstrshkbrnnn » Wed Apr 15, 2020 7:07 pm

Maybe this is a stupid question.... but where would I find a proper check valve to perform this test correctly. Is there a specific part number, or could I borrow one from the vacuum line system already in the car? Also, could I use a boost gauge? It reads to about 15psi, but maybe its not quite sensitive enough? I apologize if the questions I'm asking are unclear.
'94 854 NA 287k (bought for $400)
'98 s70 GLT 243k (bought for $250 currently non running)
'96 854R 173K (bought for $900)
'88 245 DL who knows (bought for $600)

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