TCV Questions on 98 V70xc

Post by **Ludermilch** » 17 Apr 2015, 09:03

Little back story. Drove the car for months and enjoyed the performance. When I replaced the PCV system ( I vented it through the dipstick before) I found the yellow vacuum hose disconnected. After the repairs and replacement of vacuum hoses the car had a huge drop in performance.

Upon further inspection, I discovered the TCV to be corroded and found a good one at a yard. Still a drop in performance.

Here is what I'm experiencing. Before the repairs I got good acceleration through first, rpm dropped to 3000, and it pulled great through second, rpm to 2800 in third and would continue to accelerate.

After reconnecting the yellow vacuum this is what happens. Same acceleration through first. Once it shifts into second, it boggs down, like loss of boost from 2800 till 3500 then boost seems to kick in. Same for third gear.

Basically what's going on that it has more performance without the TCV connected and what problems would that cause?

Thank you so much.

Post by **mecheng** » 17 Apr 2015, 09:46

You can quite easily blow your engine as you are not activating the waste gate. WOT at low RPM, with high boost will bend your rods. Check your vacuum lines to the TCV.

Post by **scot850** » 17 Apr 2015, 10:25

mecheng makes good points. Check the pipes to the TCV are connected correctly (if in doubt check IPDUSA web-site for their aftermarket TCV, there is a pdf on fitting that gives which pipe goes where). Also as suggested check all the pipes as they are prone to cracking with age. They are a bit of a pain to fit, but well worth the effort.

Finally, TCV's tend to reduce in effectiveness with age. I noticed a huge improvement when I replace the TCV on my 98 V70XC.

There may be other stuff going on but start there.

Neil.

Post by **Ludermilch** » 22 May 2015, 09:59

I think I have it figured out. The TCV seems to be working as designed. It's my waste gate setting. I discovered it would open with just a lb of pressure. The valve spring is probably worn. I don't need a heavy duty one. So I set it to activate at a little higher pressure and now I get boost after the gear changes.