mysterious oxyen sensor - Page 2 - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
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post #16 of 38 (permalink) Old 06-13-2019, 05:20 PM Thread Starter
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How possible is it that the Throttle body is leaking. after another smoke test it looked like it was coming out of where the spring is. This may explain the double whammy bank 1 lean!
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post #17 of 38 (permalink) Old 06-14-2019, 07:16 AM
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Long term fuel trims are exactly that. They are from many short term samples. Try disconnecting the car battery. That will reset the pcm. Of course it will take some driving time for pcm to relearn.

If your fuel trims are still way off, time to get the smoke machine back out. The intake manifold can leak, as well as all the 20+ year old vacuum lines. Don't forget exhaust system from exhaust manifold to cat for leaks that cause unmetered air to be pulled into engine.

Your scan pics are inconclusive, as readings have to be seen second by second to determine proper sensor readings. For obd 1 car owners, the pc based program called "Freescan" was perfect for posting to forums. It recorded the data stream and you could play it back in real time. That way a complete picture of sensor activity could be seen.

Unfortunately, I'm not familiar enough with obd 2 scanners & programs to recommend 1 that has similar data playback capability.
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post #18 of 38 (permalink) Old 06-14-2019, 10:46 AM Thread Starter
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Have you ever heard of a throttle body leaking? I see smoke coming out of the spring. Not bellowing like it did from the elbow but enough to raise an eyebrow. Tonight, Watson (the smoker) and I will check for exhaust leaks as well
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post #19 of 38 (permalink) Old 06-14-2019, 12:19 PM
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Thottle body is like a carburetor that only lets air into engine. Just like a carb, when spindle bearing & seals go bad, air can be introduced to engine. And since this air would not be counted by the maf, it would cause changes to air fuel mixture.
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post #20 of 38 (permalink) Old 06-15-2019, 01:30 PM Thread Starter
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Should there be vacuum in the air pump lines during normal idle with pump off? I read about a stop switch valve but was wondering if there was any acceptable amount. After plugging the intake to the pump my short and long trims started to fall. After looking at your website I also don't think I have the AIR recall/ extra vacuum control line

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post #21 of 38 (permalink) Old 06-16-2019, 07:18 AM
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The valve that controls air pump flow to exhaust is built into the pump. There are check valves in the lines to prevent reverse flow or air when pump is running. Pump is electric & controlled by pcm.


Pump forces air under pressure into exhaust system and should never have vacuum. I suspect that system is not hooked up correctly if you are getting vacuum in air pump lines.
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post #22 of 38 (permalink) Old 06-17-2019, 11:13 AM Thread Starter
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after plugging the exhaust air ports a got the short terms to go down to 0 with the long on bank 1 still stuck at 25 and on bank 2 at 10. I know there must be a small leak in the throttle body because I did see a little smoke come from there but not like the elbow. One crazy think I don't understand is sometimes the trim will jump negative. This morning when I started it up bank 1 short was at -37 for a minute with the long still at 25 then like magic will jump back up. I recorded data as I was driving and at one time the long term was down to 10 then a few frames later jumped to 25.

more on the 02 sensor
this is the 2nd sensor I've tried and is a delco. It still wont jump around like the bank 2 sensor. it just seems sluggish alternating at half the speed of the other side. ive tested the wires and I have power and ground. when started cold it almost seems like it alternates more normal and will reach up to .9 v which is when I got the -37 shtft but after the car is properly warm it slows down and will only reach up to .5

Im starting to wonder if all these exhaust fumes are getting to my head.

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post #23 of 38 (permalink) Old 06-17-2019, 12:33 PM
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As long as the O2 changes readings and doesn't stay at the same mv number most of the time, it is doing it's job. The O2 that is changing more rapidly just means the pcm is having to add or subtract more fuel then the O2 that is changing readings less often.


You probably do still have a small vacuum leak. And maybe an exhaust leak to go with it.. Have you tried disconnecting the battery for a few minutes? This will reset the pcm. And after pcm relearns settings, O2 & fuel trims might be better.


Is the exhaust still smell like unburned fuel?
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post #24 of 38 (permalink) Old 06-17-2019, 01:52 PM Thread Starter
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you prove a good point on the o2 sensor status. I have tried disconnecting the battery but will again. the exhaust does still smell like unspent fuel but less then when we started so thank you again. Do you recommend anywhere in particular to get the throttle body rebuilt? What may cause my short fuel trim to be -37 when it is cold?

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post #25 of 38 (permalink) Old 06-18-2019, 06:25 AM
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I don't know anyone that rebuilds throttle bodies, or if the parts are even available to do so. Try to find a carburetor rebuilder in your area. See if they can rebuild your tb.

The only other thing would be to buy a new tb. Stay away from the larger than stock one's. You'll end up with a whole new set of air/fuel problems.

Fuel trims should be higher with engine cold. Not in the - reading. You might consider engine problems being present in addition to the vacuum/exhaust leaks. Worn piston rings allowing a lot of blow by would feed the blow by into the combustion chamber to be burnt with the fuel. Maybe that's what your smelling.

Bad valves or valves not closing all the way do to incorrect valve adjustment could be allowing unburnt gas to exit cylinders into the exhaust stream. I believe it's time for a compression check and cylinder leak down tests to be performed.

Or maybe it's time to hire a witch doctor to drive away the evil spirits residing in your car.
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post #26 of 38 (permalink) Old 06-20-2019, 08:44 AM Thread Starter
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I hooked the smoker up to the tail pipes for about 45 mins yesterday and only got a small exhaust leak after the bank2S2. Beleive me i prayed i would find on preO2 sensor leak. lol.

I reset PCM to all trims were 0 after the smoke test and as soon as it hit closed loop it they jumped back up again. Im not sure if it was all the mineral oil in the exhaust but it smelled a whole level of terrible after that startup.

After that I one by one disconnected and plugged the vacuum at the manifold for the EVAP, PVC and line to under the TB, line to right valve cover and its inlet to the TB, line to the EGR, distributer, even brake booster with almost no change. Im not pround of this but i even put an oversized balloon over TB covering all the spring and assembly with no change. (not saying i got a perfect seal)

The fuel trims are always the worst when the car is idling. watching them as I drive down the road sometimes but only sometimes the bank1LT will even get down to 10 but as soon as I come to a stop they come back up to 25.

I notice when I disconnect a vac line completely. it idles up. and the short trim goes up at about 10 which makes me this this must be a massive leak or problem to get the long term at a constant 25

For the first time ever I got P1133 insufficient switching for B1S1.

I know I tested it before but for kicks is my PCM/ sensor ground the same as the diagram for a 93? (above the starter)
Every once in awhile I get a B2S2 heat circuit code. Is it possible its effecting them all?
Is it possible this Camaro is actually from the "depths of the underworld"? At this point its making my exgirlfriend look like a saint

This weekend I will do a compression/let down test

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post #27 of 38 (permalink) Old 06-20-2019, 01:55 PM
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Have you checked the intake manifold itself. It's seal can leak and admit extra air. Also, since you have not owned the car since new, consider the possibility of high performance internal engine mods.


Pcm would need to have a tune for the mods installed. If you have an obd 2 tuning program, read your Pcm's bin file and compare it to stock 97 bin file. You can download many Pcm bin files at the gearheadefi forum.
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post #28 of 38 (permalink) Old 06-20-2019, 02:22 PM Thread Starter
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high performance engine mods? this day might turn around after all. LOL That's a good point too. I assumed it already had at least some tranny work done bc it churps 2nd gear religiously.
I do not have the obd2 tuning program.

the only way I have checked for intake manifold leak was through the smoker into one of the vacuum lines and I saw no smoke from the intake manifold. If it was leaking out and not from the top would it travel into the space drained by the PCV? Now that you say that I do remember a slight bit of smoke coming out of the PCV when the smoker was hooked up. I thought the smoke may have traveled through the right vac line into the right valve cover and through.

Either way I think I should be telling people it has internal engine mods now

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post #29 of 38 (permalink) Old 06-20-2019, 08:52 PM Thread Starter
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now that I think about it I bet if I ran the smoker with the pcv valve off and crank case line on the right side blocked I could tell if the leak was from going under the manifold.

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post #30 of 38 (permalink) Old 06-21-2019, 07:20 AM
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Sounds like a plan. Let me know results.
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