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  Topic Review (Newest First)
Today 02:51 PM
Danomax6.6 I see what you mean. That was tested with the line on with the engine off, and on at idle. I have not noticed any fuel in the line. I will retest the fuel pressure next. thank you.
Today 01:12 PM
bobdec01 Pulling that vac line increases fuel pressure, so injectors are going to pump in a little bit more fuel but not a lot since your PSI numbers are pretty close. Your FP test in post #33 only showed 3 psi difference between high and low ranges, did you test with vac line off (acceleration/ low-no vac/higher fuel pressure) and then with it connected (idle/ high vac/ low fuel pressure ) Is there any raw fuel entering the the intake from the regulator vacuum line ?



Coco.. I've been using the old OBD1 scan programs (Tunerpro, CAT's, TTS Datamaster,Scan9495) for years, has there been any LT1 OBD2 free software that developed since I've been away from the LT1 mainstream the past 5 years. Sure could use it here, I'm so used to fixing problems with data logs that I'm running out of ideas.
Today 12:31 PM
Danomax6.6 Thank you for the reply! unfortunately I do not have scanner capabilities to know the different tuning cells. HOWEVER! after disconnecting the fuel pressure regulator Vac my bank 2 to dropped to 0 long and short term fuel trim and Bank one dropped to 0 and +10! The line to it doesn't appear to be crack bc I can plug the end going into the fuel pressure regulator and the trims stay low. The weird thing is that the regulator seemed to be working correctly when pluged in but maybe there is a leak in it somewhere?
07-07-2019 11:22 AM
bobdec01 Danomax, pic attached is very old log from my 1994 LT1 back in the days when it was stock and prior to any tuning. Ignore the DTC 77 as I was doing some home brew messing with the fan switching, prior to tuning the fans it. The log is at idle on a warmed up engine, in closed loop (BLM Enabled). Remember there are 19 BLM cells, idle uses cell 16, an will show any vac leaks as much higher due to the TB being closed and higher vacuum being pulled. Also when you plugged the PVC vac side of the system there is also a PVC input to the engine that feeds MAF measured fresh air to equal whats being sucked into the intake (keeps trims balanced). It's a hose on the right valve cover to the TB on the '94, not sure where it is on the '97. If you plug PVC vac to crankcase then any blow back will go thru that open hose to TB and could be why trims changed.
What are your readings at idle in BLM cell 16 ? . MAP , ST trims, BPW (injector Pulse widths), INJ DC (injector duty cycles), AFGS (air flow gms/sec), TPS%, TPS voltage, IAC position, RPM, IAT (input air temp) , spark advance and retard. I know your scan tool may not have all these diaplays but the more the better.
07-05-2019 03:49 PM
Danomax6.6 Compression test on Bank 1 was #1 155lbs #3 155lbs #5 150lbs #7 155lbs.
PCV valve, Throttle body, and an evap line replaced with no change.
I will check compression on the other side tomorrow.
I still dont understand why even the long term on bank 1 will sit at 25 at idle and jump to 3, then 10, then back to 25 while driving.
What are normal values for MAP, MAF, on a stock motor at idle?
06-25-2019 09:46 AM
Danomax6.6 It certainly has been. Ive made more progress on this issue in a few weeks then in the years ive owned it and that is thanks to you.

Fuel pressure test: within normal limits of the of the service manuel. (42psi when primed and about 39 during idle. once turned off fuel pressure holds loosing only 10 psi over night.)

Compression test: Still trying to get my hands on a let down tester might just buy the harbor freight one.

Throttle body: ordered with delco TB gasket.

Beers: running dangerously low

Unfortuanly due to my upcoming board exam further tests will be postponed until next weekend
Ill let you know the results of the next few test. Thank you again
06-23-2019 06:38 AM
cocobolo95 94-97 use same throttle body. Yes, new intake gaskets would be good. Be sure to follow directions in 96 service manual. Use a good grade of silicon sealant on front & rear of intake. Let it skin before screwing in bolts. Then just snug it up. Let silicon cure for 24 hours before tightening down & torquing. bolts.

Only guess I can make as to why fuel trims increase when pvc system is plugged is; pvc system sends out oil vapor which has O2 mixed in. When system is hooked up, this extra O2 is being sucked out of engine. When plugged, the O2 is somehow getting into the combustion chamber causing leaner O2 readings and causing pcm to increase fuel.

This has been a long thread. Did you ever put a fuel pressure gauge on fuel rail to see if fuel pressure was within proper limits during idling & different driving conditions?

When you do leak down test, you will be listening for air flowing from combustion chamber to oil pan, intake system, & exhaust. If you get air in pan, you have piston, ring, or cylinder problem. If you get air in intake, intake valve problem, or mis adjusted intake valve. If air in exhaust, exhaust valve or adjustment off.

One last place to look will be air coming out of valve guide. And test must be performed with that cylinder at top dead center, on firing stroke. That is with both valves closed. If test is done with piston in any other position than tdc on firing stroke, you'll get air going out either intake or exhaust valve or both.
06-22-2019 03:38 PM
Danomax6.6 Results: no smoke into the crankcase after a solid 20 minutes on the machine. Still some smoke coming out from the arm with the spring of the throttle body.
Will a 94 Throttle body be the same as my 97? I found a brand new one on ebay. it looks the same but I figured you would be the guy to ask.

https://www.ebay.com/itm/LT1-5-7-Thr...w/254264800566

Before I buy it I will do a compression and let down test but my thoughts are if 1psi of smoke can get through it its probably not helping the problem.
Furthermore, If I do buy I feel like I should just do the intake gaskets to be safe.

One last thing. I noticed with I blocked both the PCV valve and the vac line of the left side the fuel trims actually got higher. Why is this?

This may be normal but both o2 sensors stay pretty close to the .6/.7 mark at cold start but drop low after 30 seconds.
06-21-2019 07:20 AM
cocobolo95 Sounds like a plan. Let me know results.
06-20-2019 08:52 PM
Danomax6.6 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.
06-20-2019 02:22 PM
Danomax6.6 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
06-20-2019 01:55 PM
cocobolo95 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.
06-20-2019 08:44 AM
Danomax6.6 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
06-18-2019 06:25 AM
cocobolo95 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.
06-17-2019 01:52 PM
Danomax6.6 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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