Problems surrounding the Turbo Control Valve and Vacuum Lines

mitch944 · Post by **mitch944** » 23 Sep 2018, 17:29

Hi All,

A few weeks ago, I noticed that the turbo on my car had either stopped working or lost a lot of power. I had the code P1238 for Turbo control valve. Its a 99 S70 GLT

I got a TCV from the junkyard and replaced it, along with 2 of the vacuum hoses (couldn't reach the 3rd). Then sprayed Electrical Contact Cleaner in the connectors for the TCV and Mass Airflow Sensor and put it all back together.

As I test drove it I applied throttle to engage the turbo, it worked for a second or two then I heard a POP. Not very loud but a pop. The turbo then quit again and the car drove like it had no turbo at all.

Then today, the car would drive for a minute or two then not rev past 1500 rpm and be very sluggish and 'coughing' on the road. would only throttle for a second then go to almost zero RPM. I checked my work and found that I had switched the 2 vacuum lines that I replaced. I fixed it but nothing changed.

The car now has symptoms of a bad Mass Airflow Sensor:
Sluggish acceleration
Very rich smell like fireworks or sulfur
RPM at idle bounces up and down until it stalls completely.

I am wondering if this could be a MAF issue? But I feel there is probably a bigger problem with the TCV and turbo but all the symptons point to MAF.

Thanks in advance

WhatAmIDoing · Post by **WhatAmIDoing** » 23 Sep 2018, 17:45

Have you checked your charged air / intercooler piping. If one of those pops off or splits, you will have similar symptoms. Also, the TCV units are known to fall. Not sure what damage you can do hooking it up backwards. Also, if your wastegate diaphragm is bad, you will get no boost.

Post by **scot850** » 23 Sep 2018, 17:57

Have you checked the CBV? It has a diaphragm inside which will split with age. One of the 3 pipes from the TCV runs down to the CBV. By removing it at the TCV end you can try to pull a vacuum on that pipe and see if the CBV can hold the vacuum. Even sucking on it may be enough to give an idea. One of those hand held vacuum pumps for bleeding brakes is useful as they sometimes have a gauge on them which helps to identify if the vacuum is holding. You can do it with a unit without a gauge but you will have to see if it holds a vacuum.

Also go around and check all the turbo hoses from the inlet from the air-box to the inlet manifold and use a mirror to carefully check that none has come loose or the rubber hoses has split. Also check the intercooler as best you can see for cracks.

Neil.

mitch944 · Post by **mitch944** » 23 Sep 2018, 18:10

WhatAmIDoing wrote: ↑23 Sep 2018, 17:45 Have you checked your charged air / intercooler piping. If one of those pops off or splits, you will have similar symptoms. Also, the TCV units are known to fall. Not sure what damage you can do hooking it up backwards. Also, if your wastegate diaphragm is bad, you will get no boost.

Thanks for the reply. The rubber portion the the intercooler pipe was replaced about 2 years ago.

I am wondering - if the vacuum line from the wastegate was plugged into the wrong solenoid port, maybe it was unable to accept the waste air and led to too much pressure in the wastegate and then POP.

I just started the car and unplugged the Mass Airflow, then it ran smoothly. I drove it for about 20 mins, which was long enough to where symptoms should appear if it was the MAF. I had it up to about 50mph and was all good, but I didn't try the turbo.

Will still try to narrow down the turbo problems

mitch944 · Post by **mitch944** » 23 Sep 2018, 18:13

scot850 wrote: ↑23 Sep 2018, 17:57 Have you checked the CBV? It has a diaphragm inside which will split with age. One of the 3 pipes from the TCV runs down to the CBV. By removing it at the TCV end you can try to pull a vacuum on that pipe and see if the CBV can hold the vacuum. Even sucking on it may be enough to give an idea. One of those hand held vacuum pumps for bleeding brakes is useful as they sometimes have a gauge on them which helps to identify if the vacuum is holding. You can do it with a unit without a gauge but you will have to see if it holds a vacuum.

Also go around and check all the turbo hoses from the inlet from the air-box to the inlet manifold and use a mirror to carefully check that none has come loose or the rubber hoses has split. Also check the intercooler as best you can see for cracks.

Neil.

I have not tried this, thanks for the suggestion. It will be next on my list. The junkyard near me has an s70 GLT wagon that was in amazing shape when wrecked. I'll see if I cant get one off it

Post by **rspi** » 23 Sep 2018, 19:45

A turbo car can NOT run without the turbo. You don't "try" the turbo, it always spins.

Post by **abscate** » 24 Sep 2018, 04:55

Since it’s math day at MVS there are3! Combination ways to attach the hoses on the TCV

These six ways are:

Correct way
Red to compressor housing
Yellow to wastegate
Blue to snorkel dump port

If you swap the yellow and blue, with red correct, the solenoid will be applying pressure to the wastegate at the wrong time, so boost won’t be regulated and will be on all the time!

If you put red on yellow , yellow in red, and blue correct - it should work as designed?

( stopping here to check colors)

Post by **erikv11** » 24 Sep 2018, 11:39

I agree with others that WhatAmIDoing cited by far the most likely problem, loose or cracked hoses in the intercooler path.

mitch944 · Post by **mitch944** » 24 Sep 2018, 11:51

abscate wrote: ↑24 Sep 2018, 04:55 Since it’s math day at MVS there are3! Combination ways to attach the hoses on the TCV

These six ways are:

Correct way
Red to compressor housing
Yellow to wastegate
Blue to snorkel dump port

If you swap the yellow and blue, with red correct, the solenoid will be applying pressure to the wastegate at the wrong time, so boost won’t be regulated and will be on all the time!

If you put red on yellow , yellow in red, and blue correct - it should work as designed?

( stopping here to check colors)

Good info.
It was the yellow and the blue that were switched

Post by **erikv11** » 24 Sep 2018, 12:19

Thanks for reporting back! All good now with them switched back?