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Discussion Starter · #1 · 11 d ago

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 21 but does slowly creeps down to 16 and then back up ( ignition timing or valve springs) ,I also checked the fuel pressure 45 psi.

I have attached a screen shot 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?

I am beginning to think it is mechanical problem like a weak or broken valve spring that is causing a misfire that is dumping unburnt fuel into the exhaust manifold and tricking the 02 sensor resulting in the wave form or lack of below.

Thanks for any useful input.


Gary


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Have you tried switching left & right O2's to see if problem goes to other side of engine? If it does then O2 is your problem.

If it stays on same side, after switching O2's then suspect wiring, connectors, grounds.

Hope when you bought a new opti that you bought a GM, Delco, or Delphi opti. All the rest are junk. I suggest buying a PC based oscilloscope to check opti low & high resolution pulses for proper square wave with no drop out or waveform changing.

You can get a PC based scope for around $70 on ebay, amazon, etc. I'd also download the 96 factory service manual at the following site. It has driveability & emission section, as well as full wiring diagrams.
 

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Discussion Starter · #1 · 11 d ago

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 21 but does slowly creeps down to 16 and then back up ( ignition timing or valve springs) ,I also checked the fuel pressure 45 psi.

I have attached a screen shot 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?

I am beginning to think it is mechanical problem like a weak or broken valve spring that is causing a misfire that is dumping unburnt fuel into the exhaust manifold and tricking the 02 sensor resulting in the wave form or lack of below.

Thanks for any useful input.


Gary


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My 93 vette with 40,000 miles is in the shop today replacing the cheap opti I installed with a new ac delco because of the same problems you have. I bought cheap got cheap....
 

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Discussion Starter · #4 ·
My 93 vette with 40,000 miles is in the shop today replacing the cheap opti I installed with a new ac delco because of the same problems you have. I bought cheap got cheap....
Let me know if does any good. I replaced mine with an aftermarket OPTI but it did not make any difference. Let know if it helped or otherwise solved your issue. Did installing an OEM AC Delco Opti solve the problem yes/no ?
 
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