Subject: Re: Great write up! What is the purpose of this air pump? Author: jbarton750 : member since December, 2004 : 182 posts Posted on: 2005-03-01 15:46:41

It pumps fresh air into the exhaust manifold at startup to fool the oxygen sensor into reading proper fuel mixture ratio. Without it, you would get a check engine light because your emmissions would be too rich.

• Secondary emissions air pump replacement procedure (pic) (url) - DavidC 2005-03-01 14:37:47 (31616 views)
  • Don't forget to replace the EGR valves, too! (url) - DavidC 2007-04-27 12:48:45 (1219 views)
    • Do I have this on my 97 740il? (nt) - alexe 2009-09-03 16:28:39 (40 views)
  • More info in a followup thread found here. (url) - DavidC 2005-12-09 12:19:44 (1139 views)
  • Re: Secondary emissions air pump replacement procedure - mortyk 2005-03-01 20:42:45 (1203 views)
  • Nice! Any other symptoms like SES, check engine or the like and - Magnum 2005-03-01 16:02:59 (1022 views)
    • There were no other symptoms and the SES light didn't illuminate (yet) - DavidC 2005-03-01 20:49:41 (1103 views)
      • Interesting, because after this post I listened to my car upon start up - Magnum 2005-03-01 21:41:59 (927 views)
        • Yes, a slight noise outside is normal, but not a loud noise that drowns - DavidC 2005-03-01 23:02:43 (844 views)
  • Damn. That's the longest extension I've ever seen! - sealbeach740 2005-03-01 15:39:53 (779 views)
  • Great write up! What is the purpose of this air pump? (nt) - silber98 2005-03-01 14:56:31 (1101 views)
    • Re: Great write up! What is the purpose of this air pump? - jbarton750 2005-03-01 15:46:41 (1316 views)
      • My Volvo has a similar pump... - txdarth 2005-03-01 18:45:50 (907 views)
  • David, do the V-8 4.0 liter have this pump also? - Gary 2005-03-01 14:42:51 (856 views)
    • Re: David, Great Article & Good Job!!! (nt) - HighLine740iL 2005-03-01 18:16:42 (760 views)
      • Re: David, Great Article & Good Job!!! - 81xavieromar 2006-02-28 18:19:11 (485 views)