Does the '90 have an incoming temp sensor? It is mounted in the silver intake runner going to the TB. If you do have this, remove it, spray the tip with some carb cleaner, then re-install. This sensor can get gunked-up over time from the charged air being slightly oily. This tells the ECU to limit boost depending upon if the temp of the incoming air is high.

What about the O2 sensor? It may not be faulty enough to illuminate the CEL, but might be wreaking havoc with the ECU/boost. Try removing it, and cleaning the tip with a propane torch, then re-installing.

Checking vac lines might not be good enough. You may need to replace the lines altogether. Many vac line leaks are pin-hole sized, and upon increased boost, grow to a larger size allowing a greater leak. There is also the vac line that goes to the in-dash boost gauge which can also be leaking. This one is sort of hidden within the firewall/dash. I would think a '90 would definitely be in need of new vac lines. I know my '93 900T needed them. You should also inspect the plastic "T" and "Y" fittings that the vac lines attach to, as well as the rubber grommets under them.

Removing the "W" line from the BPC proves that your turbo is capable of attaining wild boost. Obviously, this means there is something wrong with either the BPC or a sensor (telling the ECU to limit boost). It is quite possible that the "new" BPC you purchased is not working correctly either. I went through two O2 sensors because the first one, although brand new, was not good.

Does the cruise control system work? If not, I know in the classic 900's this would cause a limited-boost issue. Is this the same in the 9K's?

What about the charcoal cannister system? Functioning correctly? I know this is another probable cause of boost-issues in the c900's.

Whew, I'm drained now...

Joe
'98 78K
'93 900TC 129K

posted by 12.111.48...

• Batter up! Who can solve this one?, AK Colin, Tue, 24 Aug 2004 14:29:00
  • Does a 90 9000 have an engine knock sensor?, My, Winder, Thu, 26 Aug 2004 07:34:12
  • Some other ideas..., Joe98, Wed, 25 Aug 2004 10:30:43 <-- Viewing This Message
  • Have you put a vac gauge on it so you know, Noel, Tue, 24 Aug 2004 16:56:38
    • Re: Have you put a vac gauge on it so you know, AK Colin, Tue, 24 Aug 2004 17:05:06
  • I'm in the SAME exact boat with you, its not even funny, gavin, Tue, 24 Aug 2004 16:31:07

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