the car idles from 1100 rpm and surges to 1750 and back again. only happens in park. goes away in drive. plugged in a code reader and got po135 bad o2 sensor. it does not tell me if it is the top or bottom one. i am assuming once i put it in i own it and can't return it so i would like to do the right one first. how do i find the right one? is there a most likely one to fail?

 

http://www.troublecodes.net/honda/hondaobd2.shtml

If you need to buy a new one, make sure it is OEM, and buy it online to save money.

 

secondary (back) o2 will not have an impact on performance from what Ive read

 

i just did a motor swap. could i have put the top sensor in the bottom and the bottom one in the top? would it make a difference?

 

? anyone?

 

Year make and model of car?

Make/model of engine?

 

97 civic lx 1.6

 

P0135 is the primary/top oxygen sensor.

You really need to pull the two bolts out of the heat shield on the exhaust manifold and look very closely at where the top 02 sensor screws into the manifold - those cars are notoriuos for having the manfolds crack, and subsequently throwing a primary o2 sensor code P0135 or P0141.

That's why I asked year/make/model.



Oh and you said you swapped the engine - is it stock?

 

there is definitely a crack. saw that when swapping the engines. i just figured that would have a small exhaust leak. bummer. guess i need to replace the manifold instead of the o2 sensor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by allisonmo2 &raquo;</TD></TR><TR><TD CLASS="quote">there is definitely a crack. saw that when swapping the engines. i just figured that would have a small exhaust leak. bummer. guess i need to replace the manifold instead of the o2 sensor?</TD></TR></TABLE>

I'd change the manifold and the sensor.

If all you did was change the sensor the code would be back soon enough because of the crack in the manifold screwing with the readings.

If all you did was change the manifold chances are the sensor itself is bad too now.

 

total run time has been less than 5 minutes. do you think it would kill the sensor that quick?

 

if you just bought it, go exchange it for a new one.

also, is that manifold crack not still warrantied? I thought they extended it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by allisonmo2 &raquo;</TD></TR><TR><TD CLASS="quote">total run time has been less than 5 minutes. do you think it would kill the sensor that quick?</TD></TR></TABLE>

What about the car it came from?

 

as for the warranty i am at least the 3rd owner so that won't help. and i will check the donor motor when i get home tonight. the motor i swapped in cam with the manifold already on it so i didn't bother to swap it.

 

my 97 civic is doing the same thing... idles all wierd and crazy in my situation its the secondary sensor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boosted16z6 &raquo;</TD></TR><TR><TD CLASS="quote">my 97 civic is doing the same thing... idles all wierd and crazy in my situation its the secondary sensor</TD></TR></TABLE>

I've never seen a secondary o2 sensor affect idle wuality and make the engine run crappy.

Are you sure you don't have any more codes?

 

the downstream sensor is ONLY used to monitor catalyst effiiciency and has nothing to do with engine performance!! if your idle is fluctuating then try closing the SAS screw some, check for vaccuum leaks and the iacv aswell. The reason it is doing so is because the idle is too high and the ecu is seeing that and cutting fuel pulse fom the injectors to help lower the idle.

 

okay, so back to my problem for a minute. swapped the exh manifold back to the original engines one and still have the same surging problem once warm. the funny thing is when i put it in drive it idles just fine. still sound like an o2 sensor? i just want to be sure before i plunk down the $ for a new one since i can't return it.
thanks

 

nope...

 

any other ideas then since po135 is the only code i get

 

well i replaced the o2 sensor and my cel is gone. but i still have that surge in park when it warms up. when i put it in gear(automatic) it idles fine all day. it will jump up to about 1750 rpm for about a second then fall back to 1000-1100 then back up again.


so now what?

 

again .... check for a vacuum leak, sas screw adjustment, and check the iacv....