1998 T5 O2 Sensor and Vacuum Lines

[mecheng]

After doing a spark plug change, I reset my ECU and the P0133 code for the front O2 sensor has not appeared but it might be a matter of time. Before trying to change the O2 sensor because it is pretty much welded to the bung, I stumbled upon this:

https://www.matthewsvolvosite.com/tips.p ... rottlebody

There are 2 seperate posts from PAUL and LARS for vacuum lines causing O2 sensor codes, can anybody verify this? Does anybody have pictures of the hoses they are referencing, it is not clear from the post.

Thanks

[erikv11]

It is very common for vacuum or intake leaks to cause O2 sensor codes. In fact, more common than actual O2 sensor problems.

So you do want to thoroughly inspect all of the vac lines etc., e.g. the ducting to the throttle body intake too. Make sure everything is tight, look for cracks in the small lines and tears in the big ones. Any old and crumbly vacuum lines just replace, your car will run better longer, you can just use generic rubber vac by matching up the inner diameters.

Lars is referring to the famous "p0172" hose, get a flashlight and peer in underneath the power steering pump you will see it recessed back in there. Paul is referring to that one and/or the line from the vacuum tree to the fuel pressure regulator. These are key, common failures but you just need to check them all, get in there and look around at the various lines.

[mecheng]

I could not see any vacuum hoses under the PS pump. Here is a pic. The zip tie is for the ECT, the previous owner broke the tab on the wiring harness.

Under the PS Pump

I took a picture of two hoses that go into the intake that are rotted, they are adjacent to the throttle body which I cleaned.

Rotted Hoses Going in to intake manifold

What is this vacuum hose and the thing it connects to under the radiator shroud?

What is this vacuum line

[erikv11]

The line behind the PS pump is more like between the thermostat housing and the intake manifold. It hooks onto a nipple on the end of the manifold. This picture shows it well, with the manifold tilted up out of the car:

ibxfth.jpg (56.84 KiB) Viewed 1158 times

The black and white thing is a check valve. I don't know where that hard plastic line goes to offhand, you may have to trace it. It is fine to replace that hard line with a rubber or silicone line. The rotting line should be replaced too.

[mecheng]

The line behind the PS pump is more like between the thermostat housing and the intake manifold. It hooks onto a nipple on the end of the manifold. This picture shows it well, with the manifold tilted up out of the car:

ibxfth.jpg

The black and white thing is a check valve. I don't know where that hard plastic line goes to offhand, you may have to trace it. It is fine to replace that hard line with a rubber or silicone line. The rotting line should be replaced too.

Oh that looks like a bitch to get too, I'll try tonight, thanks!

[erikv11]

You can get to it OK with those really long nose pliers. You'll want a flashlight to eyeball it.

[matthew1]

The line behind the PS pump is more like between the thermostat housing and the intake manifold. It hooks onto a nipple on the end of the manifold. This picture shows it well, with the manifold tilted up out of the car:

ibxfth.jpg

Good photo. Here's a couple of the evil P0172 elbow "in situ".

[mecheng]

Great pics, I found it, it appears to be okay. I'll do a carb cleaner spray test on it tonight.
I did one Readiness test, apparantly I have to do 2 minimum? Soooo anonying, luckily I did it at 1 am and the roads were somewhat clear. No codes yet.