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  Sept. 29, 2010 7:48 a.m. 1988RedT2 Reader

  So it seems like I just fixed the convertible top issues and everything is looking swell and she starts running rough for the first 20-30 seconds or so on a cold start. I figure something with the VANOS system and I'd sort it out when I got around to it.

  Well, last night, the usual rough running smoothed out and she set a CEL. I pulled the codes this morning: P1421 and P1423. Referring to the amassed wisdom of the interweb, I deduced that this has something to do with the secondary air injection system. Lovely.

  I'm in the process of checking operation of the valve at the exhaust manifold. Should the pump run when I turn the ignition to the "ON" position? All I hear is some little gizmo near the throttle body making a light clicking noise. and a humming noise coming from under the intake manifold somewhere.

  Car is '97 328iC. 71k on the clock.

  Any advice is appreciated.
  

  Is this CEL even likely to be related to the rough idle on cold start?

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  Sept. 29, 2010 7:58 a.m. Giant Purple Snorklewacker SuperDork

  BMWs use a blower at start-up that only runs during the first 90 seconds or so - a little longer in cold weather. It satisfies the emissions without having to run all the time sapping power. The blower motor, sitting in the pass side rear of the engine bay is dying. It is a common problem, solved in one of two ways...

  • remove it and plug/weld the holes in the exhaust manifold and replace the secondary O2 sensors with dummys to turn off the light.
  • replace the blower motor

  If you go with the 1st option I'll sell you a set of welded manifolds I have laying around my garage for $50. If you go with option 2... I may still have the blower from my 98M3 in the basement but... its probably close to death as I had 85k on it when I removed mine (to make it a racecar).

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  Sept. 29, 2010 8:08 a.m. 1988RedT2 Reader

  In reply to Giant Purple Snorklewacker:

  Yeah, given that this is my wife's sunny day cruiser, I'll probably opt to keep it stock. I see that the blower is a tad pricey.
  

  The valve checks out fine. Given that a faulty valve is the most common cause of blower failure, maybe there's hope for mine?

  Turning the key "ON" and checking for airflow at the large hose to the valve yields "NOTHING". Blower does not appear to be running at all. Is there a fuse or relay that controls it? I checked the main fuse box, and it doesn't appear to live there....

  Thanks for your input!

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  Sept. 29, 2010 8:17 a.m. Streetwiseguy HalfDork

  In Volvoland, the blowers fail after they fill up with condensation from a leaky check valve. Considering the relative prices, I'd put a check valve on it too.

  Ther blower is commanded on by the ECU. There will be a relay somewhere that is the blowers power supply, probably fed by a largish fuse.

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  Sept. 29, 2010 8:23 a.m. Giant Purple Snorklewacker SuperDork

  I don't have a wiring diagram in front of me - I'm at work... but I'm sure there is a fuse in the chain. The ECU controls a relay to on/off the pump. Test that as well. Could be a weak field if the fuse is OK.

  Try juicing the motor with 12v 1st - if it spins easily and the fuse is good - replace the relay. If the fuse is popped be wary, it could seem OK but be drawing more current than it should because its dying. Assuming you verified the valve is fine so the load on the motor is ok. There are usually signs before the motor goes. It gets loud.

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  Sept. 29, 2010 8:26 a.m. JtspellS Reader

  

  Upper left hand corner is where it is like said and the valve is due south of it (just past the end of power on the exhaust side of the engine)

  My 98 323is had the same issue before we had to trade it and usually if you are going to do it there are some bushings at the bottom that hold it to the bracket that should get replaced. GL

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  Sept. 29, 2010 8:41 a.m. 1988RedT2 Reader

  Appreciate the help so far. I have news!

  Just got back in from the garage. I pulled the valve off the exhaust manifold and it is closed. Applying vacuum to the diapragm opens the valve. Operation seems fine. Judging from the appearance, it wouldn't surprise me if this part was replaced by the PO.

  I re-installed the valve, re-attached the vacuum hose, and left the large air hose disconnected. Then I fired it up and pulled it out. As I got out of the car I was greeted by a noise kinda like a Hoover at full scream. Not a bad sound, just a high speed blower and healthy rush of air. Blower seems fine also.

  So why am I getting codes P1421 and P1423?

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  Sept. 29, 2010 9:04 a.m. 1988RedT2 Reader

  So now I'm hot on the trail of the "air pump vacuum control" which seems to send the vacuum signal to the valve. Durn thing appears to be tucked up under the intake manifold where only a mouse could find it.

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  Sept. 29, 2010 12:41 p.m. Entropyman New Reader

  I had to track a similar issue. All my components were good but the system still didn't work. I finally just re-plumbed the vacuum system using a new check valve and it has worked great ever since. I will eventually replace the old components and neaten things up when I pull the intake manifold this winter.

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  Sept. 29, 2010 1:08 p.m. 1988RedT2 Reader

  In reply to Entropyman:

  Did you ever replace the vacuum switch under the intake manifold? I'm leaning that way right now. I still need to see if it's doing what it's supposed to be doing. Gotta find a vacuum gauge. I used to own one. Don't know where it's run off to.

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  Sept. 29, 2010 1:17 p.m. Giant Purple Snorklewacker SuperDork

  1988RedT2 wrote:

  In reply to Entropyman:

  Did you ever replace the vacuum switch under the intake manifold? I'm leaning that way right now. I still need to see if it's doing what it's supposed to be doing. Gotta find a vacuum gauge. I used to own one. Don't know where it's run off to.

  Yeah, if all the components downstream of the ECU are functional, look at what it uses to make its decision. Engine coolant temp, f-idle status... etc

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