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Re: More cool O2 sensor stuff (archive)
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Posted by Frank on November 18, 2001 at 14:34:08:

In Reply to: More cool O2 sensor stuff posted by Todd Kenyon on November 18, 2001 at 13:01:55:

Ever replace coolant temp switch?
Decided to use O2 sensor to see what is going on when my cold driveability problems act up. Problem is of course that the sensor normally takes about 60-120 secs to start working, so by the time it kicks in the car would already have warmed up. So I rigged the sensor heater inputs directly to the accessory block next to the fuse box. The red wire here is always on 12V. So I got everything ready (had O2 sensor disconnected from DME), and gave the sensor heater 12V for 2 mins before starting the car. On startup, got immediate readings on mixture with engine totally cold. Looked pretty rich until I started going. AS I approached 3-4000 rpms where I typically loose power, the needle went to ZERO. or extremely lean. The car started it's usual surging behavior, which coincided with the needle jumping up to rich and back to lean. After the ususal 2 mins or so of driving, it suddenly evened out, needle swung to rich and car drove great.

So what is going on? The normal cold enrichment process seems to be falling short somehow. Yet when it switches out of this mode (which is determined by coolant temperature, and which coincides exactly with the end of the blue zone for me) it gets plenty of fuel.

So does this point to the DME? Injectors? carbon deposits? At least now I know what the negine is experiencing, even if I don't know why...




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