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Discussion Starter · #1 ·
I have a 97, z28 with only 35 k. I have been dealing with misfires and problems on bank 1 for six months. I have replaced the OPTI, injectors, plug wires, coil and O2 senor B1S1. Check for vacuum leaks, checked the intake vacuum: rock solid at 21, checked the fuel pressure 45 psi.

I have attached a screen shoot of my post warmup 02 wave form from my scan tool. You can see it's stuck way up on the rich end. I cant figure out what causing this. Any suggestions?

Thanks for any useful input.


Gary
 

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Have you tried using your multimeter to check continuity of signal wire that goes from O2 to PCM. Both ends of wire need to be disconnected when you make ohms measurement.
 

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Discussion Starter · #3 ·
I have not. My thought was that if I had no continuity the sensor would not work at all. Electricity is pretty binary. As you can see it does have a wave form just not the ideal or expected one. Plus it is a real PTA to get at that sensor harness tucked up above the cat and then location the other end on the ECM.

For some reason the car runs rich, misfires, backfires only on bank one after warm up.
So this not a bilateral issue i.e. only Bank1.

Any know rich fuel causing culprit such as coolant temp sensor, MAF and MAP would be bilateral affecting both sides.

I have installed a new OPTI thereby eliminating distributor and cap problems
Installed new injectors eliminating the possibility of poor fuel atomization
Replaced all the plug wires on that side eliminating that issue
Replaced the O2 sensor B1S1- that's what you are looking at above.
The car has only 35K and the plugs were replaced at 25K when I put the shorty headers on ( the only mod) I don't recall the brand of the plugs but they were like $10 a piece iridium's.
I did not do a compression test which would be impossible to do correctly (warm engine, all other plugs out and throttle body blocked) but I did do a manifold vacuum test and got rock solid 21 in of vacuum. I thought considering the low miles that there would not be a mechanical issue e.g. broken value spring, blown head gasket or bad rings, those would have shown up on the manifold vacuum test or would have other tell tale signs: blow by, coolant loss, water in oil etc.

I also checked for upstream exhaust leaks with Seafoam and did find a small leak where the Y pipe bolts up to the exhaust on the other side but not real bad only visible with Sea Foam and well downstream from the rear O2 sensor. But no obvious leaks from the manifold gasket on Bank1.

The only thing I have not done is check the plugs on bank 1 except # 7 which appeared fine. I do get code 300 random multiple cylinder misfire and in a few instances 305 and 307 . I just didn't think it could be a plug issue considering the the low miles and the fact they were changed 10K ago.

Any ideas would be greatly appreciated, I have dealing with this for a year!

Gary
 

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Discussion Starter · #4 ·
Have you tried using your multimeter to check continuity of signal wire that goes from O2 to PCM. Both ends of wire need to be disconnected when you make ohms measurement.

Yes, i just did it last night both wires OK , Also checked PCM for reference voltage got 5 V
 

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Have you tried switching left & right O2's to see if problem follows the sensor that is stuck at .700 volts?

The only other thing I can think of, would be to hire a witch doctor to excise the evil spirits living within your car.
 

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I have a 97, z28 with only 35 k. I have been dealing with misfires and problems on bank 1 for six months. I have replaced the OPTI, injectors, plug wires, coil and O2 senor B1S1. Check for vacuum leaks, checked the intake vacuum: rock solid at 21, checked the fuel pressure 45 psi.

I have attached a screen shoot of my post warmup 02 wave form from my scan tool. You can see it's stuck way up on the rich end. I cant figure out what causing this. Any suggestions?

Thanks for any useful input.


Gary
You didn't mention whether or not you replaced your plugs, could be a bad plug on the misfire. As far as rich bank one it could be a mechanical problem, oil burning in one or more cylinders. You could be sucking oil past your intake valve guide seals, or a broken oil ring. Try doing a wave form of the cranking amps. Set up a trigger on number one cylinder so you know what cylinders are pulling low amps.
 

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Discussion Starter · #7 ·
I tried everything and just cant figure it out. Someone on the z28 Forum said they had a similar issue and it was actually an exhaust leak. I observed that I do have a small leak in a Y pipe connector but downstream from the 2nd O2 Sensor, which has nothing to do with fuel trim.

Here is the problem again: Car runs rough and backfires
Throws code PO 132 high voltage O2 B1S1
O2 Sensor flat lines, no wave form @ .8

Things done: Manifold Vacuum 21, rock solid
New Plugs and Wires on Bank One
Checked for vacuum leaks
You didn't mention whether or not you replaced your plugs, could be a bad plug on the misfire. As far as rich bank one it could be a mechanical problem, oil burning in one or more cylinders. You could be sucking oil past your intake valve guide seals, or a broken oil ring. Try doing a wave form of the cranking amps. Set up a trigger on number one cylinder so you know what cylinders are pulling low amps.
You didn't mention whether or not you replaced your plugs, could be a bad plug on the misfire. As far as rich bank one it could be a mechanical problem, oil burning in one or more cylinders. You could be sucking oil past your intake valve guide seals, or a broken oil ring. Try doing a wave form of the cranking amps. Set up a trigger on number one cylinder so you know what cylinders are pulling low amps.
You didn't mention whether or not you replaced your plugs, could be a bad plug on the misfire. As far as rich bank one it could be a mechanical problem, oil burning in one or more cylinders. You could be sucking oil past your intake valve guide seals, or a broken oil ring. Try doing a wave form of the cranking amps. Set up a trigger on number one cylinder so you know what cylinders are pulling low amps.
Yes, I did replace the plugs, I did not do a compression or leak down test, don't see how it could be done with the lack of space, FYI, I looked for oil on the plugs when I changed them and did see any only lots of fuel. Also as I said I did pull a manifold vacuum test and got 21 rock solid, usually that will reveal issues related to low compression especially if the are that severe. On the z28 Forum said that they had a similar problem from a downstream exhaust leak. I don't see how that would cause such a problem especially if its downstream form sensor 2? I do have any exhaust leak but it's downstream from sensor 2?

One other consideration the only mod on this car is Edelbrock Shorty Headers. I ran some Seafoam through a vacuum line but didn't see any smoke coming form the gaskets or the headers only the downstream leak which is not real big.
 

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I tried everything and just cant figure it out. Someone on the z28 Forum said they had a similar issue and it was actually an exhaust leak. I observed that I do have a small leak in a Y pipe connector but downstream from the 2nd O2 Sensor, which has nothing to do with fuel trim.

Here is the problem again: Car runs rough and backfires
Throws code PO 132 high voltage O2 B1S1
O2 Sensor flat lines, no wave form @ .8

Things done: Manifold Vacuum 21, rock solid
New Plugs and Wires on Bank One
Checked for vacuum leaks




Yes, I did replace the plugs, I did not do a compression or leak down test, don't see how it could be done with the lack of space, FYI, I looked for oil on the plugs when I changed them and did see any only lots of fuel. Also as I said I did pull a manifold vacuum test and got 21 rock solid, usually that will reveal issues related to low compression especially if the are that severe. On the z28 Forum said that they had a similar problem from a downstream exhaust leak. I don't see how that would cause such a problem especially if its downstream form sensor 2? I do have any exhaust leak but it's downstream from sensor 2?

One other consideration the only mod on this car is Edelbrock Shorty Headers. I ran some Seafoam through a vacuum line but didn't see any smoke coming form the gaskets or the headers only the downstream leak which is not real big.

Did you have the misfire first or the rich bank one..? Who's injectors did you use..? New or rebuilt injectors..? LT1's are sensitive to injectors. I put a set of Accel injectors that were suppose to be the right one's according to Accel tech support. The motor ran like crap, so rich I have to change the oil. The ohm's on the coils were suppose to be 12.5 instead they were 15.8. OEM's are 24 lbs Accel were 24.6 lbs. Also an injector could be hanging open at times.
 

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your spark plug wires are probably cut for a older disributor in back off side and are pulling tight and vibrating loose .
pull every wire off put a extra spark plug in boot and make sure the boots are not too long cause they will break your connection doesnt matter 7 or 8 mm LT1s are a nightmare on mixing the wires up
theres just no room
and maybe two answers mines blue max moroso 80 bucks right lengths and numbered
but 1 of your problems is a spark plug wire
but still check the boots with a spark plug in your hand in front of your face .
go over firing order I think your front o2 sensor might be drowning in un fired gas
but part of you problem is tuneup
push the wires farther through the boot if you have too
take a paper clip and take out wires out of plastic plug on front 02 sensor dont loose where they go in plug
the 02 is a heating element and wires get hot so inspect the heck out of plastic part of plug
and check wires one at a time on o2 plug and make sure they are tight
and little tangs are pushed out farther so they click in plug better
 

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I had an issue with my ‘96 WS6 T/A, where I replaced the O2’s with all new Delco sensors, all but one would read correctly, I’m pretty confident I got an O2 sensor that wasn’t a “ Case Grounded” unit, like the stock O2’s,
(Probably an Amazon knock off that is an isolated ground sensor, like the newer LS engines have) any way’s, if you suspect that is the case, try running a separate ground wire to the Tan colored wire in the O2 harness plug,
That could solve that problem, maybe.

hope this helps,
Ben Smith
 
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