Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I think I know the answer but I just want to ask . new engine running like poo. its practically all new, but the computer says lean. it wont go into closed loop, I found a crack in the exhaust manifold, ordered a header as a manifold is no longer produced. my question is, would the O2 be stopping the system from going into closed loop?
If the pcm thinks the O2 is bad it will ignore the sensor and stay in OL. If the pcm thinks the O2 signal is valid although it´s at fault the engine will enter CL ( if all the other conditions are met). Based on the faulty O2 signal the pcm will make (fuel trim) adjustments that can make the engine run poorly.
Nevertheless, your situation seems to be different: If the pcm stays in OL id does not make any adjustments due to erronreous inputs from the O2, leading to a poor running engine So a poor running engine in OL would not be due to a misreporting O2 signal.....
Does the O2 react to fuel enrichment and did you test for possible causes of a genuine fuel delivery problem like fuel pressure/volume, clogged injectors etc?
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Yes I have checked and everything in the fuel system (new injectors) (new regulator) and a psi around 38psi . I have smoke tested the intake side and I have a tiny tiny leak near the butterfly on the throttle body. when I say runs like poo I mean it has a tad of a shimmy at idle ( it acts like too much fuel) and the bank one 02 sensor does react when you rev it up but at idle it is flat and very low. If I recall it is somewhere near .002 volts. the engine is flooding you can smell it when you sit very long, but the ECM is giving a P0171 in pending and never writes it. I realized the crack and it is a pretty large one by smoking the exhaust. it is on the #4 runner and after research it is pretty common with this car. I already ordered the header as it needs to be replaced I will report back after install I was just curious if a 02 sensor (it is heated) could stop the closed loop status. in the code it does say engine not getting to temp./ however the ECM shows the temp between 180 and 185. I also checked the ohm of the temp sensor and it is in spec. when I unplug it the readout goes to -40 and if you jump it the temp goes to 347 I feel that the ECM is working right and the only thing I can find is the crack in the manifold. also both 02 sensors are brand new
What do both of the oxygen sensors read? Front and rear? If the rear reds full Rich I’d check the actual signal with a multi meter or scope and compare to scan data
