LS6427

iTrader: (2)

Oh, ok, gotcha.

What exactly are we looking for? What temp at the time of break-up would tell us something?

Is there an exact temp my 1998 goes into open loop?

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joecar

Something else to look for:

with scantool monitoring command of EVAP, AIR, EGR, take note if the problem coincides with those being commanded on/off.

LS6427

iTrader: (2)

AIR and EGR have been removed.

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98Camarod

iTrader: (43)

There's a table that tells you what temperature it's commanded to go into closed loop. If you log those basic parameters, you should be able to find exactly what's doing it.

LS6427

iTrader: (2)

Hey, just thinking......can one bad 02 sensor make the other sensor throw codes?

Like if the Bank 2 sensor is wacked for sure......can it cause the other one to throw "slow response" and "low voltage" codes?

Or will the Bank 1 side run great no matter how bad the Bank 2 sensor makes thing run for that side?

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98Camarod

iTrader: (43)

Generally the slow switching is due to the o2 sensor not being close enough to the heat source, like with long tubes. I had this problem before. I ground down the bung to allow the 02 sensor to stick more into the header and that problem went away.

LS6427

iTrader: (2)

I've had my 02's in the same spot for 9 years so I guess that can't be my issue.

I was just gonna change out both of my 2 month old 02 sensors and see what happens.....before tearing into electrical things or trying a new PCM.

Just a thought....I'm still gonna get a full HP tuners log while its breaking up....hopefully someone here can make sense of it....before I do anything.

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.cammedZ

iTrader: (4)

FWIW I have experienced this before and it turned out to be a bad O2. When the car was started cold the o2 voltage would not come down fast enough, taking too long to heat up and start reading properly. This high voltage would make it think it was too rich when it would switch to closed loop and pull all kinds of fuel temporarily- buck, hesitate, stumble, then come out and run fine. Took me a while to catch it just right on the scan tool to see what was going on.

LS6427

iTrader: (2)

Cool.....cause we checked everything else possible so far. I'll get some new 02's ordered, they're cheap enough. Thanks.

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