O2 sensor reading!!

[UnhuZ]

Hi guys,

my friend installed the GT-One headers and GT-One Titanium (the same as Vancehu) without any cats ...it's a 91 nsx.... and... the CEL lights up...sometimes it takes a good half hour of driving arround, others it takes about 30s. The code is for O2 sensor.

the sensor was replaced but the problem persisted.. we switched the O2 from one bank to another and the problem persisted on the same bank..

we then checked CO emissions, and the good bank showed a reading of "1,5" and the bad one read "6" lot's of gas on that one...

what was my line of thought???... lot's of gas...so...i think it can be 1 or more of the following:
1 - bent or burnt valves
2 - injector malfunction
3 - coil pack malfunction
4 - spark plug malfunction

number 1 is out because a compression test showed a perfect match between all 3 cylinders

tomorrow we will take out the injectors to have them tested

new spark plugs will be installed

will test the coil packs (have new ones and my own ones to test)

i ask you guys what you think of what would the problem be and if my thoughts are good ones

thanks very much,
Nuno

 

[Briank]

There are 2 codes for each o2 sensor which one are you getting?

 

[UnhuZ]

Hi Brian,

when i read the CEL code list (prime faq) i see that the 2 codes are only for OBDII...this is a 91 NSX...

now...there is something strange here... because the code read is "2" (Rear O2) but the richer bank is the front one....

today we made some tests and when we retrieved the codes, there were 3 new codes :

43 - Front Fuel Supply System
44 - Rear Fuel Supply System
15 - Ignition Output Signal

now...as both 43 and 44 are shown, and only one o2 sensor code (the rear one) i think the problem could be before the 2 fuel rails, somewhere between the fuel tank and right after the fuel filter...

the 15 code, i don't have a clue, need some help on that one...

i find hard to believe that the install of the complete GT-One exhaust system (headers + muffler) could bring all this problems!!!

 

[Briank]

Check the vacuum line to the fuel presure regulator. What o2 code are you geting the 1 - 2 or the 41 -42, both could be caused be bad o2 extension cables or the cables melting on the headers.

 

[UnhuZ]

will check the vacuum line..

the o2 codes are the "2" not "42" :wink:

the extensions were checked with a multimeter and the headers are all wrapped up to stay warm and cosy the longest :biggrin: :biggrin: :biggrin:

thanks dude,
Nuno

PS -sometime soon i'll send to you the 2 AC CC that i mentioned sometime ago by PM :wink:

 

[Briank]

Are they new 02 sensors or reused ones, if you reused the old ones that could have been mechanically damaged or contaminated with penetrating oil used to remove them in either case they will need to be replaced with new.

 

[UnhuZ]

reused ones...we have tried with 4 different ones....the 2 originally from the car, and other 2...the results are always the same, wherever we plug each one

 

[angus]

wiring problem

 

[Larry Bastanza]

Check to make 100% sure you do not have the front 02 sensor connected to the rear connector and visa-versa. When you install headers, with the change in position of the front 02 sensor wire this can easily happen.

If the two banks get switched, and I have seen this a few times before, the ECU is confused because it is controlling fuel for the wrong bank of cylinders.

HTH,
LarryB

 

[UnhuZ]

Larry, that could be possible...but is not the case here ahheahae

an update... a important one:

these appened right after the install of GT-ONE F1 headers and GT-One Titanium v2.1 (the same as Vance's)... i never thought by changing the complete exhaust line, that a problem could arise beside the O2 sensor damage by uninstall them from the old headers. So i thougth that the problem would be elsewhere.

My friend sent an email to Hitoshi from GT-One... his reply made everything clear... the O2 sensors from NA1 (and don't know if NA2 till 2001) are a little restricted in terms of reading and can't handle the flow with the complete exhaust...he said that the exact same thing appened to his red NSX, this appen worse in the front bank besause the header line is more straight backward (!??!!? thought both had to have the same speed)..

his cure to the problem: Use late OEM O2 sensors ... this make some sense, because TURBO2GO didn't had any problem like this (right dude? :biggrin, and he has a 02+ :biggrin: :biggrin: :biggrin:

what you guys think of this???