Stuck in my secondary air system diagnostics (no vacuum from manifold?) - 1.9

[elgolfo]

Hello forum,

As of two weeks ago, I am the owner of a 1998 Z3 1.9 L. This forum has been a great help so far in working on my to-do list, but I now I am stuck.

I get fault codes P1423 and P1174 and found that my secondary air system is not functioning. I mostly followed this great guide, and found big holes in hoses 13 and 9 on the diagram below.

While I ordered replacements, the most important problem seems to be that I get no vacuum from the nipple at number 7 ("Container" - 11 61 1 312 762). Now, I have no idea whether this points to a lack of manifold vacuum, has to do with a broken "container" or more likely, more holes in hoses 5, 3, and 1. The latter would probably also explain the hissing noise in my engine bay. How can I access those hoses (5,3,1) for testing, they seem to be buried underneath the engine?

If I need to start removing parts for access, what else should I be looking out for, as I have read of CCV, oil separator faults and other things, but have no idea whether this could apply here or what/where to check and don't want to do this massive job more than once, but have parts ready in case I need them.

No overly rough idle, by the way.
Thanks a lot for your help!

[rf900rkw]

All the vacuum plumbing is surely rotten at this age. You will have to replace it. Your mixture code and lack of vacuum to the control valve hint that the lines under the manifold are done. Yes, they are nearly impossible to access with the manifold in place. I strongly recommend pulling the intake manifold off, replacing all the vacuum lines, fuel lines, and coolant pipes and hoses.

[elgolfo]

Thanks, although that doesn't sound like a lot of fun at all. Is there a kit I could purchase? Is there a good write up? And finally, what mechanical units should I purchase in advance to make sure that I have them on hand in case they turn out to be rotten, too?

I really wish there was a way just to replace the vacuum lines without taking apart the entire intake manifold. Again, I don't get rough idle nor bad gas milage.

I think I'll go to one of these DIY shops in the Bay Area and try my luck unless any of you nice folks are planning a similar sort of thing at your place, then I could swing by

[elgolfo]

Update:

I decided to take off the intake manifold, replace its gaskets and also replace the CCV and the hose that connects the CCV to the intake manifold. This will be a major project for me and I want to make sure that I have everything on hand that could cause hose 9 not getting any vacuum. Therefore:

Where does hose 1 come from? If there is no leak in this hose, it must be a problem in whatever this connects to. What could cause hose 1 not getting any vacuum?

What other parts should I have handy for this repair? I read of fuel lines but I cant find a kit or summary of the needed parts.

[elgolfo]

Ok, in case anyone wonders about this in the future: The source of my vacuum leak was hose 5 and 3 in the diagram above. It is indeed only possible to replace these with the upper intake manifold removed. I used this Pelican Parts manual for help. From the T-Splitter, I still don't know for sure where hose 1 connects to, but I suspect it runs underneath the intake manifold back to the very front of the engine (which is actually accessible with the intake manifold in place, but that doesn't help if it needs to be replaced as you can only access the vacuum source, not the end that connects to the T-Splitter). The other hose from the T-Splitter runs underneath the car in the vicinity of the fuel filter.

[2santiago]

Glad you solved your issue. I replaced 13 last month, went through the proper drive cycles and passed the emissions test here in Chicago, IL.


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