P1238 Turbo Control Valve

bobice · Post by **bobice** » 20 Jun 2010, 12:27

I hope to get more advice with a new post - Previous post

The main symptom of my 2000 volvo V70 XC at 168000 Miles is the engine cycles from ~200-1000 rpm during idling (frequency at ~ 2 seconds). When I press the gas pedal, the engine can turn faster. The code is P1238: Turbo Control Valve.

If I disconnect the MAF sensor, the engine can run fine (in a limb mode?).

Since I tried one after-market and one Bosch MAF sensor already, I think MAF shouldn't cause this. From another post on the code P1238, I was told this code could also be triggered by Vacuum leakage, or throttle position.

So where is the throttle and how to check if it's functioning?

Also, have anyone replaced vacuum hose and the turbo control valve? How about the turbo control valve from IpdUSA?

Thanks!

Post by **jblackburn** » 20 Jun 2010, 15:57

That turbo control valve from IPD is awesome. It livens up the turbo response before 2500 RPM a lot on my car...from what I understand, it helps the XC's a lot too.

Before you replace it, check the vacuum lines first! There are 3 from the valve on the back of the air cleaner box to the turbo charger area. Inspect all of those for cracking, I know mine were pretty far gone.

Your problem sounds more to me like the ETM though, affecting the idle issue.

You can try cleaning it, but you may have to look into a re-built unit. Check out Don's ETM room in the list of forums here and do some reading to see if those sound like your symptoms.

bobice · Post by **bobice** » 20 Jun 2010, 16:08

jablackburn wrote:
You can try cleaning it, but you may have to look into a re-built unit. Check out Don's ETM room in the list of forums here and do some reading to see if those sound like your symptoms.

Thanks! But how to go to Don's ETM room? I tried to look under the Volvo Forums, but it isn't listed.

Post by **jblackburn** » 20 Jun 2010, 17:33

Here you go:

https://www.matthewsvolvosite.com/forums ... m.php?f=12

If you just click the volvo forums link at the top of the page, you will see it in the listing page there.

Since you have a '99, you have an electronic throttle module (ETM) rather than a throttle position sensor on your car. The strange idling up and down can be a symptom of a failing module, or it may just need to be cleaned. But hopefully some things there will explain it a little better for you.

Post by **schmidm90** » 22 Jun 2012, 16:28

Does anyone know where instructions are to replace the TCV? I am probably going to replace the lines this weekend to eliminate my P1238 code. I am also going to the junk yard tomorrow morning to get a "new" MAF, TCV and EVAP valve to eliminate all those possibilities.

My Volvo idles fine, but it stutters around 3500rpm and then will jump up and down 200rpm and then idle fine. I tried to unplug the MAF and it idles the same with/without the MAF plugged in.

Post by **matthew1** » 22 Jun 2012, 16:47

It's easy, just pop the new(er) one on and keep all the lines in the same place as the old TCV. The lines are color coded.

Post by **schmidm90** » 22 Jun 2012, 17:19

Thanks Matt! Do you know any place locally that would sell silicon hose to replace the lines? I know IPD sells it, but that is a few days away and I was hoping to give it a shot this weekend. Thanks again for all the input!

Post by **matthew1** » 22 Jun 2012, 17:34

I use Gates 3/16th vacuum line. I get it at my local auto parts store. Make sure you buy vacuum line, they might try to mistakenly sell you fuel line.

Post by **schmidm90** » 22 Jun 2012, 21:20

Matt, which store is it? Would autozone, CAP or advance autoparts have it? Also is this a hose I might be able to get at a hardware store such as Lowes or Home Depot?

Post by **matthew1** » 22 Jun 2012, 23:03

O'Reilleys, but I'd expect to find it or similar brand at any auto parts store. Home improvement stores, anyone's guess.