Ive tried to run a search on 02's and their functions, but the search engine wont allow it.

I have a few questions on O2's and hopefully this can become a sticky for everyone's benefit.

What do o2 sensors do, and what can happen to an lt1 if they go bad?

I, for example, blew a header gasket on my pacesetter lt's, and i noticed that after driving around with the leak, I believe, as well as other mechanics, that I burned one of my o2s.

I would like to know if, assuming the 02s are out, what damage would be caused to performance? That is to say, it is normal for me to be losing low end power, as well my temperture rising, or are those coincidences????

As for the temperture rising, Ive noticed that the 160 is not working anymore, and Im drifitng more into the middle of the gauge in my daily driving, as opposed to my constant 160 degree.

 

A leaky header gasket will cause the car to run rich causing loss of power. If your O2's are out or fouled, get them replaced. Most likely the sensor wires got burned on the headers.

 

By the way, Pacesetter gaskets are crap..get the Percy's dead soft aluminum gaskets. As for the temperature rising, my guess is that the headers are causing more heat under your hood.

 

The O2 sensors help the PCM control the A/F ratio for "normal" driving. The PCM tries to keep the A/F ratio switching back and forth from slightly above 14.7:1 to slightly below 14.7:1. That "dithering" helps the cats to function, first storing up small amounts of excess air (O2) as it breaks down the NOx, then using the stored air to oxidize unburned HC's and CO.

The O2 sensors tell the PCM whether the A/F ratio is rich or lean, so it can keep it near 14.7:1.

If the O2 sensor is faulty or damaged, the feedback to the PCM will be incorrect, and the PCM will start incorrectly adding or subtracting fuel, thinking that the A/F ratio is incorrect. That could cause your engine to run excessively rich or lean, and lose power.

 

thanks for the responses.

i apologize for not being clear. i just changed the header gasket with mr. gasket lt1's, and i noticed that upon changing the gaskets, i still had a loss of power.

now, when i say loss of power, what i mean is that the car is not awake till a little over 1800 rpms...it really takes its time in 1st to wake up, but once i pass the rpm marker, it runs...

would this have anything to do with bad o2s? or my bigger question is, what would be causing this car to run the way that it does? according to what injuneer says re: the o2s...that may be the culprit

 

guys.

responses are welcomed.

 

Did the new header gaskets seal the leaks? If the header flanges are warped, it could still be a problem.

From what you're describing, the engine has no power whatsoever up to 1,800rpm, then suddenly wakes up and performs normally? Does this depend at all on whether the engine is cold or warm?

With the limited data, its hard to pin it on the O2 sensors. If they were causing the PCM to incorrectly "subtract" fuel, it might cause it to run lean, until you reach the transistion point to "PE" mode (a table based on rpm and throttle position). But that's all just speculation.

What year engine did you put in the car? What year PCM? Is it "really stock"? Have you ever had it scanned? Any data logs?

 

Injuneer, allow me to start off by saying thank you for all your input on the boards...you are a very helpful member/moderator, and that is hard to find these days!

with that said, Ill be a little more specific. I have a 95RS swapped out from a 3.4/a4 to 5.7/m6. The car is 95. The motor is 96. The engine harness, interior harness, and relay harness, as well as the computer is off a 94 obd1.

Mods include:
Pacesetter LT's
Taylor 8.5s
MSD ignition coil
ac delco o2's installed while the motor was being put in.
moroso cold air
1le elbow
40 series flowmaster.

Now, I installed Mr. Gasket Header gaskets, and it seemed to have solved the noise from inside the engine compartment. I have a gut feeling that the c-clamps holding the y-pipe to the collectors has gone bad, but ive taken it to a few shops, and everyone disagrees with me. they say i have no leaks there. As for the flanges, the bolt on just fine to the heads.

From what I described in terms of the no power till 1800, it really does it all the time. It doesnt differ from the time it is cold, or hot.

I dont know what else would cause a loss of power downlow. Ive always been told that loss of power at low rpms (and again, when I say loss of power, i mean torque. I went up a steep parking lot, and i literally floored it till it got to 2000 rpms) is due to overheating...is that true??? i really dont have any overheating problems...

im so lost.

 

Thanks for the positive feedback....

I can understand your confusion... doesn't seem real easy to solve. I'm just sort of poking around trying to see what the possibilities are. Your original post indicated that the engine appears to be running warmer than it used to be? Did the loss of power correspond to the engine temps increasing?

Has the engine ever had the power you expected since you swapped it in, including below 1,800rpm?

It would be interesting to see how the TPS voltage and the MAP signal respond to the initial push on the throttle. Does it feel like it might be running lean when it lacks power? Is there any evidence of a misfire? Any audible signs of knock/detonation? Any chance the inlet elbow is folded under, and not sealed to the throttle body?

 

NO PROB...ITS THE TRUTH! YOU'VE HELPED ME OUT COUNTLESS TIMES!

Now going back to the question at hand, I realized the problem with the heating as of late, and it may have to do with the fact that it is gettin hotter down here in miami..lol!

but, again, no, it did not correspond with the engine temperture rising. Its been giving me that problem before the temperture issue. I just thought one would have to do with the other.

in terms of the engine having the low end power, it did immediately after the swap. low end power was all over the place.

I agree with getting the diagnostics...TPS and MAPs to start off.

there is no evidence of misfire; i installed new plugs and wires recently.
no knocks/detonation that can be heard
and the elbow is just fine

 

Sounds like it might be a head gasket leak,

have you noticed any smoke/steam comming from the exhaust?, creamy looking oil or oil in the coolant?

Do you have the tools to check for a vacume leak?

Have you reset the computer since the new header gaskets? maybe the pcm has some really bad learned fuel adjustments for near idel conditions. Also maybe try and unhook the o2's and the MAF and reset the comptur then take it out for a spinn.