So you’re saying anywhere between 0-3000 rpm if you “get on it” its bogging down ??...if in 3rd and you do it it’s fine ??...where are your long term fuel trims sitting right now...just want to know if it’s been lean ??...does your Tech 2 show show MAF grams/second or voltage...look at that at idle and under load !!...my 01 is around 7 grams/sec at idle...should go up to around 190 grams/sec at WOT !!...both upstream O2’s should go RICH under acceleration !!

Rob

One Test Is Worth 1,000 “Expert” Opinions”

You have a Tech 2...a factory scan tool !!...you can see if you are in open or closed loop just by looking at live data...you'll be in open loop when 1) cold engine when first started, WOT, heavy accel and decell,...if you had a fixed O2 sensor either rich or lean that will force it into open loop AND you'll have a DTC. can't remember if there are any others. You should NOT be in closed loop during these conditions...Like I said I usually don't diagnose just based on symptoms...you gotta test !! ….like I said look at fuel trims, MAF PIDS, etc... You can disconnect the MAF and let it run off your MAP sensor...it will throw a DTC and run rough for a second or two after starting but you'll see if you have the same issues while driving like you have now. You said it "seems" like the O2 are working...do you know what the O2's are supposed to look like under various driving conditions ??...I'll include a link to O2's and fuel trim operation...you'll learn a lot !! ...look at part 2 about the 3:50 minute mark into the video...he explains MAF diagnosis with fuel trims !!...long term fuel trims are what most diagnose driveability issues with but some forum members may disagree...in the video we are looking at the LONG TERMS !!!

They are hot enough !!!...You'll have issues if the O2 heater circuit is inoperative after startup...you'll be in open loop then and stay there and a DTC will set...when the O2 sensors are warmed up you'll start to see the fuel trim numbers starting to move either positive or negative...your are now in closed loop...check that with your Tech 2...during idle operation the upstream O2 sensors will be switching between 200-800 millivolts or so...the down streams will be kind of steady somewhere around 450 millivolts....just remember....LEAN IS LOW (below 450 mv) and RICH IS HIGH (above 450mv)....if O2 around 200 it's lean...if 800 it's reporting rich !!

He probably should have gotten a misfire DTC...either P0300 or cylinder specific...without some testing you just don’t know !! :)).
With that Tech 2 OP just has to get some data together !!

You Tube

Just looked at my Autel...it doesn’t read MAF voltage..just airflow...ask a forum member who might have one...I think my man Froggy just bought one...I can tell you how to check it...with MAF unplugged you should have your 5 volt ref. on the yellow wire, 12 volt on the pink and ground on the black/white which is a body ground...G106 !!

NO !!!....you need a multi meter !!...you have one ??

Ok, you’re GOLDEN then !!...like I said you can find out if any member has a Tech 2 if you want to know if it should read 0...you have a VERY powerful diagnostic tool in your hands...you just have to know how to interpret what your looking at !!...there are some excellent YouTube videos on diagnostics where you can REALLY learn...IF...you have the desire !!...Paul Danner...AKA “Scanner Danner” in my opinion is the best out there hands down...I have been following him for years and if I have a question he always has time to reply !!

I’m reading 5 volt ref. KOEO with connector plugged in...that’s “probably” what your scan tool is probably reading...you might be missing your 5 volt ref. if you said it reads 0 !!...the 5 volt ref. is shared between other sensors...another sensor MAY be dragging it down...or you have an "open" in that circuit...if you get to this point and may need help let me know !!

PERFECT !!...that’s your 5 volt reference !!

:cheers:

Hi !!...usually O2 sensors that are usually starting to get “lazy” are starting to go bad...did you use an aftermarket sensors on the ones currently installed or OEM ??...and when going bad they will indicate lean...what do your long and short term fuel trims look like ??...as far as the hesitation I don’t know if I mentioned it but disconnect your MAF sensor and see what happens when you drive it...it will throw a DTC so don’t worry...also, do you know how to graph your TPS 1 and 2 voltages with the Tech 2 ??...with the key on engine off slowly push the accelerator down and release and look at the TPS signals...they should not have and drop outs or spikes in the signal...you can try this for now !!...good luck !!

Another question before you change the O2...have you ever cleaned your MAF sensor ??...I think you said you had a Tech 2...did you look at MAF airflow or frequency at idle and WOT...I prefer looking at frequency...can you try that ??

Looked at the top snapshot and it looks like the O2 is fixed rich...is the downstream O2 rich ??...normally you would see the short term and long terms fuel trims go negative in this case..,what did the downstream O2 look like ??... Other snapshots O2 looks strange also !!...did you ever look at the TPS voltages with the Tech 2 ??