2001 V70T5M Less Than (Stage) Zero

dux02v70 · Post by **dux02v70** » 21 Aug 2015, 10:12

I'm in the process of finish up a boost gauge install in my car with the gauge integrate in the cluster surround. I'll post about that separately when it's done (as long as it doesn't look like a hack job!) but I got the gauge plumbed in and the numbers don't look too good. I'm seeing 6.5 in Hg vacuum at idle and 4.5 psi max boost. I put pressure to the gauge and it is reading accurately on the boost side at least. I will confirm the vacuum later today.

I previously had a 1998 V70 T5M and that car would absolutely blow the doors off of this car. I figured it was not building full boost but I didn't expect it to be this far off. It idles smooth, accelerates smoothly (if not as quickly as I expected) and there are no codes.The idle vacuum is steady and the boost snaps right up to 4.5 psi and stays there. Not sure where to start but I must have a big leak somewhere, right?

mika · Post by **mika** » 21 Aug 2015, 10:30

did you check the wastegate actuator?

dux02v70 · Post by **dux02v70** » 21 Aug 2015, 10:34

Haven't checked anything. I'll start tearing into everything this weekend but I was just wondering if low vacuum and low boost together typically pointed to any specific issues.

Post by **kallekula** » 21 Aug 2015, 11:30

On idle you would typically see around 20 in/hg depending on if your'e in P or D and/or if AC running.
If not, start chasing vacuum leaks. And that is best done with a smoke machine. Go to a shop or build your own. If the leak is big u can hear it.
That low reading would probably set a CEL after a while due to the cpu will add more gas.

dux02v70 · Post by **dux02v70** » 21 Aug 2015, 11:42

That's what I would have thought too. I'm surprised to not see any codes so I'm going to double check the gauge as well.

I can set up a smoke machine if needed, but a thorough check of the hoses is in order first anyway. Is there any significance to the max boost being the same as the base setting? seems like an odd coincidence. If the TCV is stuck closed then that could happen, correct?

dux02v70 · Post by **dux02v70** » 21 Aug 2015, 19:41

Well the TCV works fine. Hooked up a vacuum pump to the input and it held vacuum against the the wastage port, then when I triggered it with 12 volts it bled off vacuum. So there's some money saved but one possibility off the list.

Post by **kallekula** » 22 Aug 2015, 14:12

dux02v70 wrote:Well the TCV works fine. Hooked up a vacuum pump to the input and it held vacuum against the the wastage port, then when I triggered it with 12 volts it bled off vacuum. So there's some money saved but one possibility off the list.

Do you have an obd2 reader? Whats the LTFT at? Think the cel wont be triggered until ltft reaches 20% or so?

dux02v70 · Post by **dux02v70** » 25 Aug 2015, 12:26

I'll have to check the fuel trim and see. I did find a nice split in the hose at the wastegate but when I replaced that it still tops out around 5 psi. And my vacuum is still at a whopping 6.5 in Hg. I just need to dig into it more thoroughly and check everything. Probably should pull the entire induction system and flush it, clean all the couplings and make sure it's all sealed up, check every hose downstream of the throttle body and then see where I am.

Post by **abscate** » 27 Aug 2015, 06:28

dux02v70 wrote:Well the TCV works fine. Hooked up a vacuum pump to the input and it held vacuum against the the wastage port, then when I triggered it with 12 volts it bled off vacuum. So there's some money saved but one possibility off the list.

The TCVs on these cars aren't DC solenoids, they take a higher frequency signal to control boost.

If it hasn't been replaced since original it's almost certainly sluggish.

There is a resistance spec but without some fancy gear you can't really check it with just voltage.

It's an obvious suspect for low boost

Post by **kallekula** » 27 Aug 2015, 16:42

dux02v70 wrote:I'll have to check the fuel trim and see. I did find a nice split in the hose at the wastegate but when I replaced that it still tops out around 5 psi. And my vacuum is still at a whopping 6.5 in Hg. I just need to dig into it more thoroughly and check everything. Probably should pull the entire induction system and flush it, clean all the couplings and make sure it's all sealed up, check every hose downstream of the throttle body and then see where I am.
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Replace all hoses. The turbo vacs are 4mms. Just do it