"Low" boost in a V70 2.5T

chandlerm · Post by **chandlerm** » 01 Oct 2020, 20:31

Poking around with the recording and diagnostic tools in VIDA, I'm barely reach a max of 4psi after a few hard pulls. I know this is the LPT version, but that just seems very low. This V70 has a nearly unknown service history other than basic Stage 0 stuff I've done since purchase, and what looks like a replaced engine just based on sharpie scribbling on the engine. At 195k, it's obviously got some wear and burns oil, going from full to low on the dipstick in about 3-4k miles.

Watching the wastegate/bypass valve arm, it seems to function normal but I haven't check to see if it functions normally. I also can't hear anything that sounds like a boost leak or loose vacuum line anywhere, but I might not have checked everywhere.

I know I can't get it perfect, but I'm hoping to restore at least some performance. I can post logs from VIDA if that would help anything.

Post by **- Pete -** » 01 Oct 2020, 22:05

Out of curiosity, what year?
I had some toils along these lines, but I was only boosting to 6-7-ish PSI, when I normally boost to 15 PSI on our “Stage 1” 04 XC70.
For what it’s worth, 2.5T LPT should make ~7-8psi in stock form/tune.

Aside from the low boost, the other stuff you mentioned rang true to me as well. Wastegate (& (new) TCV/MAP) functioning appropriately, MAF cleaned, all new vacuum lines, no induction or pressurized piping leaks, etc...

What I ended up discovering that helped was to unplug the ECM/TCM, spray contact cleaner, spray dielectric grease and then carefully re-install both ECM/TCM.

This proved to work for a couple thousand miles and then I noticed the problem creeping back in. Re-doing the above would always “fix” my problem for a period of time. Hot ambient temps always seemed to make the problem happen more frequently. Now that we’re into the 40’s for daytime temp it never reoccurs.

Now that I’ve realized fixing it’s more than just removing and reinstalling the ECM/TCM my next step will be to replace the ETA (electronic throttle assembly) connector and wires. I have already installed a brand new Bosch ETA and it didn’t even make hint of a fraction of an improvement.

Evidently, 2004 was one of the years known to have issues with the ETA connector/cable, thus the reason I asked what year you had.

In your situation, I would replace the TCV before anything. They are a relatively short lifespan component and pretty inexpensive. Also get a ECM/TCM removal tool - like $15-20.
Also, double and triple check your vac lines.

When the TCV fails the car defaults to make as much boost as the wastegate is set to allow - which is right around what you are making. I’m not saying your TCV is kah-poot, but it very well could be worthwhile to replace. The interval for replacement is pretty low, somewhere around 30k if memory serves me.

chandlerm · Post by **chandlerm** » 02 Oct 2020, 12:13

It's a 2004! Guess I know what I'm gonna check first then...

I'll probably get a new TCV, but since I'm going to the junkyard to get other parts for it, is it worthwhile to try a used one or should I not waste my time and just buy new?

Thanks for the reply, that helped a lot. I never found some of that info besides the TCV and vacuum line check despite digging through google and forums for a few hours.

What's also a little odd is I have 0 powertrain-related DTCs in VIDA.

Post by **- Pete -** » 02 Oct 2020, 14:03

No problem, I’ve been meaning to put my thoughts together in a thread regarding it, just haven’t gotten it done yet. Your post gave me an opportunity to jot some things down.

A new Pierburg TCV is $20-30, I wouldn’t bother buying a used one of unknown functioning.
Just get the standard Pierburg TCV, no need to take your chances with the HD TCV’s.

I also had no relevant codes to what my issues ended up being.

chandlerm · Post by **chandlerm** » 11 Oct 2020, 23:51

I've replaced the TCV, cleaned and reseated the ECU and TCM, and will be replacing the hoses once those arrive in the mail. In the mean time, I've installed a boost gauge to give me some better realtime info, and it seems to reflect what I'm seeing in VIDA.

Elz1234 · Post by **Elz1234** » 28 Jun 2022, 06:50

I have had a similar problem today with a low boost 2.5 T engine. This model is the XC70 2.5t AWD so a low pressure turbo engine. It was very slow and felt like it had no boost. I graphed the boost and found that it would boost to about 3 psi, not good.

Checking other sensors confirmed that the most likely cause was with the turbo/wastegate it’s self as the engine ran well apart from this problem, no codes or EML on the dash either.

Taking the heat shield away from the turbo showed the waste gate actuator which looked to perform normally. When taking it off it showed serious signs of wear and the slot in which the pin sits had been worn away so badly the wastegate was in effect open and flapping about.

Taking the wastegate off and adjusting the rod 8 half turns inwards gave the right adjustment so the watergate was fully closed. Almost straight away the power was back and the engine ran properly. The boost is now back up to 6 to 7 psi but there is some instability in the holding of pressure at higher rpm although this was barely noticeable. This may be due to wear on the wastegate or perhaps the vacuum control solenoid for the watergate needs changing.

To summarise, I would strongly advise anyone to take the wastegate actuator rod off and visually inspect for wear as this solved the problem for me for free and was not recommended by anyone I could find on forums.

Hope this helps someone

Elliot

Post by **jonesg** » 28 Jun 2022, 07:35

I had the same problem,
the hole in wastegate arm was wallowed out and pin from actuator arm was slotted.
I put a sleeve on the pin and drilled the hole in the actuator arm bigger to accept the sleeved pin, no more slop.

chandlerm · Post by **chandlerm** » 07 Jul 2022, 13:10

Funny enough, I just randomly came across my own thread after selling that 2.5T and having the same issue with my current R. The issue with the 2.5T was with the wastegate not being set correctly. Immediate improvement afterwards. I also had a replacement rod end where the pin slots through. Mine was slotted from wear like jonesg's. Replacing that and adjusting the wastegate fixed the issue for the 2.5T, but I'm still chasing the same issue on my R.

Post by **jonesg** » 07 Jul 2022, 19:07

heres what I did 3 years ago.
Sleeve goes over the original waste gate pin, threaded coupler drilled out to fit over the sleeve.
Tiny hairpin retaining clip no longer required.
other pic shows how much pretension I used to keep it from rattling around on the wastegate pin.

: turbo coupler.jpg (58.33 KiB) Viewed 3213 times