Vacuum pipes, Lamda lights and fault codes.

[Kernow1]

Some help / advice with a gnarly old problem please.

I have been having running problems for the last 2 months with my '97 V70 2.5T. Basically the engine, at worst after a 90 mile m/way run, will run rough for a few seconds (almost stalling if idling at traffic lights for instance), the Lamda light will come on, then it will carry on as if nothing had happened. The light stays on though.

Alternatively, on local roads it will, on the overrun at very slow speed (20 mph <), just cut out, all the dash lights come on and the engine has stopped. When placed in Park (Auto box) the engine will re-start and run OK again, although the Lamda light remains lit. Also, the Average MPG readout on the onboard computer seems to stop reading and display "diSC" for much of the time.

I got the AA to check it out twice, but on both occasions their diagnostics didn't 'talk' to my model. When I suggested selecting another model, it talked, extinguished the warning light but found no fault code.

With the light on again, I recently put the car in for a 90k service, and to get the diagnostics checked, at my local garage (non Volvo dealer). They said that the fault code indicated a 'Low Boost Pressure' code, and that they had found a split vacuum hose between the inlet manifold and the turbo. Fair enough says I, and paid up and drove away, happy that the light was out and the fault cured.

However, while driving the next day, the inevitable happened and I'm back to square one. I contacted the garage, explained, and they wiil have it back next Monday for another look. Call me cynical, but I thought that the 'fix' was a bit too easy. Especially as no such hose exists, I've discovered.

So, after combing the forum for similar problems I went out and bought a suitable Fault Code Reader. The reader worked perfectly and recorded one DTC : P 0102 (MAF A circuit - Low Output). I then erased the code and re-started the engine, to see if the original code showed up. Within 10 seconds the I/M light was back on, and when interrogated the code was this time P 0172 - (System Too Rich Bank 1(?)).

With this info I searched the forum for these codes and found two really useful threads about a MAF connecter problem, and worn vacuum pipe elbows. I checked the connector and have secured it as instructed, and went in search of the elbows. On the L/H/S of the engine (whilst under the bonnet), under the rad hose and inboard of the power-steering pump I can see a 4mm O/D(?) rubber pipe, approx. 3" long, which is connected, at one end, to the inlet manifold, but to nothing at the other end. The pipe looks a bit manky and hard, but I'm not sure what it's for. Surely not a breather?

Can anyone cast any light on what this might be? And do you think it might cause these symptoms? I'm really hacked off with Emission Controls and all the loads of little pipes that are a part of it !!!

Thanks for your patience. Any advice would be gratefully received..........while I still have some hair left !!

[Chris_Rogers]

The pipe you refer to is one that will usually give problems because of the failure of the elbow at the manifold end. The other end is at the inlet to the tubro where is connected to an electrically heated nipple. You will probably find the nipple is blocked solid and you may need to drill it out using a small twist drill held in your fingers.

there is a guide here:

http://www.volvoforums.org.uk/showthread.php?t=46946

I think if you follow this it will provide the info you are seeking.

I would advise maintenance of the PCV system and a clean of the throttle body and idle air valve.

If this does not entirely cure your problems then investigate further.

[Jod T5]

Originally Posted by Chris_Rogers

The pipe you refer to is one that will usually give problems because of the failure of the elbow at the manifold end. The other end is at the inlet to the tubro where is connected to an electrically heated nipple. You will probably find the nipple is blocked solid and you may need to drill it out using a small twist drill held in your fingers.

there is a guide here:

http://www.volvoforums.org.uk/showthread.php?t=46946

I think if you follow this it will provide the info you are seeking.

I would advise maintenance of the PCV system and a clean of the throttle body and idle air valve.

If this does not entirely cure your problems then investigate further.

Bang on Chris....
OP, you can connect a section of 4mm samco from the manifold nipple and pass this around the fuel rail and connect to the air inlet section to test if this is the issue. You will need to remove the existing elbow on the manifold and connect the samco using long nosed pliers, heating the pipe in boiling water to expand it will help....If there is a break in the brittle pipe (or it is not connected at all which seems to be the case) there will be an introduction of unmetered air into the system which will cause poor running....
Cheers
Jod

[Kernow1]

Thanks Chris and Jod.

Just a couple more questions, if you wouldn't mind please guys.

Where can I get the 4mm Samco pipe, and where is the heated nipple on the turbo situated? Does the pipe run across the complete width of the engine (Left to Right) and then back down to the turbo? (As mine seems to be broken I can't see where the other, longer bit of pipe is.)

Thanks again.

[Jod T5]

Originally Posted by Kernow1

Thanks Chris and Jod.

Just a couple more questions, if you wouldn't mind please guys.

Where can I get the 4mm Samco pipe, and where is the heated nipple on the turbo situated? Does the pipe run across the complete width of the engine (Left to Right) and then back down to the turbo? (As mine seems to be broken I can't see where the other, longer bit of pipe is.)

Thanks again.

The Pipe is part of the PCV system and runs from the inlet manifold nipple, behind the inlet manifold to the PCV heater which is located before the turbo on the inlet air tube...It will be just before the turbo.....The PVC valve should be easily identified as it has an electrical connector a fat tube and a thin (this is your one) one attached....

Not the greatest pic ever but see the yellow pipe.....and when on the right it joins a black elbow?......where the black elbow joins the main pipe there is a little stubby bit..?...thats your man.....
EDIT a better pic...
Cheers
Jod