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2G Initial start rough idle

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98spyderboost

98spyderboost

15+ Year Contributor
265
0
Aug 2, 2004
Mount Juliet, Tennessee
Hey all, I just reinstalled my rebuilt head and when I start the car it runs very rough and dies. :cry: I did all the procedures with the new timing belt and hardware. Straight edge on the sprockets, made sure the oil pump/balance shaft was in phase, crank timing, etc. I've checked the CAS position. Checked vacuum hoses, and sensor connectors. All the plugs are equally black and slightly wet. The car is completely bone stock. Posting a video below. Any ideas or suggestions beyond what I have checked so far? :confused:

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Did another log this morning. This time got it all the way to running temps and with a few more types of data. Does the O2 voltage start cycling properly only in closed loop? If so I'm seeing the O2 stay at .02V(generally). Which if this is the case then it's obviously never going closed loop. Maybe the new info will reveal something....
 

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  • Datalog 112110.csv
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The o2 sensor should start cycling in closed loop mode 10 to 30 seconds after you turn the car on, notice that last bullet in post #23. The cars in closed loop mode when you start it even without the cycling o2 sensor, its after 128 seconds that it doesn't cycle the car locks in open loop.

The only thing that log shows is that your front o2 sensor isn't functioning, just like your other 4 logs. Just starting logs and posting them isn't going to fix the car you've got to be proactive about it. Get in there and check the wiring at the ECU using the pin out I posted above. Pin 76 of the ECU receives the front o2 sensor signal so make sure its wired up and has good continuity. If it checks good replace the o2 sensor...

:dsm:
 
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Sorry I did check that. The wire had continuity pin to pin.
You said the low voltage could mean a lean condition. Wouldn't the car be running with default values after it sees the O2 isn't working? After which time the car should run fine? Does this mean something is keeping the computer from switching into open loop even tho there is something wrong with the O2? Or I have a fuel delivery issue that's choking everything out and that .02V is an actual count instead of a screwed up O2? In which case do I need to look at fuel pressure?

:banghead:
 
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The O2 sensor was replaced, twice... A bosch and a denso were both used. I have the bosch in there now.

Edit: Looking back I see that I noted a new O2 but I didn't tell you I exchanged the Denso the next day for the Bosch hoping for a different result. Sorry...
 
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Well I went for a third shot on the O2 sensor. Same result :beatentodeath: . Did a 10 minute datalog and a new problem starts running its way out and to the floor :notgood: (eventually very agressively). Perhaps the FAILPRO head gasket was to blame for all my woes... Cometic head gasket is on the way. Hopefully it will run better then...:pray:
 
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Please update this post if you get it working. I just did a complete rebuild and am having the exact same thing happen. I also changed the o2 sensor since it was not cycling like it is supposed to. I have checked everything I can and it still will not stay idling. I posted a log on the Link forums, so maybe someone there will have the answer.
 
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1fast fwd said:
Please update this post if you get it working. I just did a complete rebuild and am having the exact same thing happen. I also changed the o2 sensor since it was not cycling like it is supposed to. I have checked everything I can and it still will not stay idling. I posted a log on the Link forums, so maybe someone there will have the answer.
Click to expand...

Oh trust me I will :) Right now I'm waiting on a head gasket at studs. Should be here Tuesday. I want this to be an issue with the head gasket all along but it doesn't seem likely. So are your O2 readings as messed up as mine are?
 
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