O2 sensor replacement

[evildragon]

Ok, so my custom built PCM is complaining that the O2 sensor in my car is out of tollerance, both of them... (and my symptoms seem to match, poor gas milage and bogging until certain RPM)

I understand mainly how they come out, but when installing the new ones, is there anything special I need to do?

[silicon212]

Don't overtighten them. Thread them in and tighten them as you would a spark plug; no more. The new ones will have a substance on the threads - DO NOT CLEAN THIS OFF! It's anti-sieze.

[evildragon]

Originally Posted by silicon212

Don't overtighten them. Thread them in and tighten them as you would a spark plug; no more. The new ones will have a substance on the threads - DO NOT CLEAN THIS OFF! It's anti-sieze.

That sounds simple enough..

And here I thought it was a complicated job.. runaround

hopefully THIS will fix my hesitation problem once and for all.. (im surprised both O2 sensors went though.. then again, I've never changed them the whole time I had the car)

when you say thread them in, btw, you mean with something like plumbers tape, right?

[silicon212]

No, just screw 'em in. Keep in mind that the O2 sensor does NOT work until the temperature of the probe is at least 600 degrees F. They get hotter than that; plumber's tape won't last. Don't use it. The antisieze is all that's needed.

Heck, I'm thinking about building my next SB with Inconel exhaust valves - Teflon tape located about 10 inches downstream from Inconel valves would be pretty interesting. (Actually, these valves are designed to take a lot of heat, they find their application in turbo cars, @ $44 a pop they sure ain't cheap).

[evildragon]

Originally Posted by silicon212

No, just screw 'em in. Keep in mind that the O2 sensor does NOT work until the temperature of the probe is at least 600 degrees F. They get hotter than that; plumber's tape won't last. Don't use it. The antisieze is all that's needed.

Heck, I'm thinking about building my next SB with Inconel exhaust valves - Teflon tape located about 10 inches downstream from Inconel valves would be pretty interesting. (Actually, these valves are designed to take a lot of heat, they find their application in turbo cars, @ $44 a pop they sure ain't cheap).

That might also back up O2 sensors as the problem with my hesitation.. When it's cooler out in the morning and I go for a drive, the car runs great.. When it starts to warm up, and it gets hotter out, the car starts bucking like a bronco out of hell...

[evildragon]

I replaced the O2's today, the car still hesitates until a certain RPM.. My PCM no longer compains about the O2's though now.. But why still hesitate?

btw, this was what my old ones looked like..

http://blackevilweredragon.spymac.com/o2sensor.jpg

[Blue Bowtie]

Since your PCM is custom, or has a custom tune, we have no way of knowing what the fuel trims look like. Is there any data log or scan of the PCM data as the engine warms and loads change? A dyno graph with A/F ratios? You might be looking at a wideband O² (lambda) and A/F meter to get a handle on the problems.

Again, since the whole system is non-stock, timing curve is a big question.

[evildragon]

Originally Posted by Blue Bowtie

Since your PCM is custom, or has a custom tune, we have no way of knowing what the fuel trims look like. Is there any data log or scan of the PCM data as the engine warms and loads change? A dyno graph with A/F ratios? You might be looking at a wideband O² (lambda) and A/F meter to get a handle on the problems.

Again, since the whole system is non-stock, timing curve is a big question.

It does it with the stock PCM too.. But here's the thing, they both give different errors.. The stock PCM throws 51 and I think 53 (i lost my scan tool this morning----ehh, my fathers scan tool)...

And my homebuilt PCM gives this:

BLACK-DRAGON-HARDWARE
KERNEL V-0.7B
PCM FOR "GM L99 4.3"
KNOCK-MODULE INSTALLED:  LT4  (MIS-MATCHED, BUT NO ERRORS REPORTED)
CPU/RAM:  80286-12MHz/8MB
KERNEL ROM:  4MB
ENGINE ROM:  2MB

A FAILURE WAS DETECTED, AND NEEDS IMMEDIATE ATTENTION!

NOTICE OF FAILURE
-----------------
TIME:  8:43AM
DATE:  AUGUST / 2 / 2007
FAILURE:  UNKNOWN ERROR
SPECIAL NOTE:  RPM NOT CLIMBING AT A LINEAR PACE
CURRENT DRIVER STATUS:  4MPH, IN-DRIVE
ENGINE TEMP:  NO SENSOR (OR INFINITE IMPEDANCE)

(edited to show output from my newer OS kernel)

[evildragon]

my bad.. just checked the GM PCM, it was 41 and 43...

my PCM will be using GM OBD support in my next kernel (and hardware) update.. that way I won't need to do these "swaps" everytime...