So I've been troubleshooting some base/reduced boost issues (when engine is cold mostly) in my '92 9KT (MT,TCS) for the last couple of weeks. Things that have been replaced over the last 10,000 miles include (not all are related to boost issues): DI cassette, BPC valve, hooter valve, downpipe & cat, air filter, fuel filter, fuel pump, NTC, all vaccuum lines, and O2 sensor. I'm also running SD APC/DI and ECU chips but the problem has been around long before these were installed.

This weekend I investigated the knock sensor. I unscrewed it from the engine block and tied it up in a rag and went for a drive.

I noticed an immediate difference in the smoothness of the acceleration and how well it held boost at WOT. There was no stumbling or backing off at all. However, after a few minutes of driving, everything was reduced to base boost and the check engine light came on.

The CEL flashed twice and then four times. I checked some older posts and these pointed to the MAP sensor and the coolant temperature sensor, respectively. I let the car sit overnight with the battery disconnected to hopefully reset everything so that I could start fresh again in the morning.

This morning I reconnected the battery and went for a drive. The CEL was gone and the car was behaving like the night before. Again, after a few minutes I was reduced to base boost and the CEL was on again with the same codes.

I screwed the knock sensor back in to the block and the CEL went away and full boost was returned.

I'm wondering why I would get those two codes with the knock sensor removed (but still connected electrically, of course). Also, I'll be damned if I can even find the MAP sensor in my car. I've scoured the past posts here and looked in my Haynes manual but it is flat-out not where it's supposed to be.

Any help on why I'd get these codes with the knock sensor removed and where my MAP sensor is would be great appreciated. Also any next steps would be really helpful.

Thanks.

• knock sensor removed, now CEL (longish), boomshnka, Sat, 26 Mar 2005 12:13:08 <-- Viewing This Message
  • Re: knock sensor removed, now CEL (longish), Jim Kane, Sat, 26 Mar 2005 13:16:27
    • You don't have a MAP sensor....., Ron J, Sat, 26 Mar 2005 14:30:51
      • Re: You don't have a MAP sensor....., boomshnka, Sat, 26 Mar 2005 14:45:27

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