These are 3 code I found on my 98 gt.

P0500 - Vehicle Speed Sensor fault.
P0171 - System Too Lean - Bank No. 1.
P0174 - System Too Lean - Bank No. 2.

new plug and wire with 2 new bosch o2 sensort, my car is smoke alot the other day and water was coming out the tail pipe, I lucky enough to fix it with head gasket repair, now it no or very little smoke when start up, after its warm up no more smoke . Could it be water destroy my o2 sensort ?

and my idle is around 800, when I put the gear to neutral to brake the car, then edometer is point at 1500 and after the car complete stop, few second later it drop down to 800 ?

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Okay, don't hate me for it, but the simple solution has to be asked... you did disconnect the battery when doing the swap to reset the computer right?

 

check for vacuum leaks

 

Yes the battery has been dis the whole time.

 

Here's a list of trouble codes and what they mean. Check to see what it says, maybe it will help.
http://www.paladinmicro.com/PalMFrame00.htm?wks=obd

 

thanks

 

First off, clear the codes and drive it until they come back on to make sure the swap didn't cause them somehow. The speed sensor has nothing to do with the PI swap so if it comes back on just replace the sensor. The lean condition sounds like a vacume leak so check all your vacume hoses and your intake pipe to make sure it's all the way on the throttle body and clamped down. If everything looks good there try changing the o2 sensors.

 

Take start fluid and spray in possible leak areas and if the car revs u found ur leak. I did the swap just the other week and the car started and ran fine. It did take almost a day of driving around for it to really get used to the new intake though.