NA O2 Sensor Question

[brian300zx]

I have been having a weird issue where when I start my car it hesitates pretty bad on a cold start but as soon as it gets to operating tempsture it’s completely fine. I’m thinking it’s my O2 I have no CEL, I’ve checked my injectors, I’ve cleaned all of my connections, as well as checked the AICV unit. I’ve also ran the O2 test and it came back good. I can remember after a Plenum pull I had a CEL that said I had a bad driver side O2 but after driving for a few miles it went away. My guess is the O2 heater core is messed up. What do you guys think? The prices of the O2 are kind of ridiculous otherwise I would have just bought them.

[macgiver]

mac here, same engine I have (J30), and I'm going to give a kind of tunnel-visioned answer , for so many things can do this - simply replacing things , unless your rich ,is frustrating time-consuming and pricey . So here it is , I believe a good "first diagnostic" is to start car , when it is doing this ( don't let it warm and have symptom disappear) - running badly for the few minutes SHUT it OFF , remove all spark plugs (fairly easy on these!) - mark them , observe any fouling oil or gas , broken , differences in color etc. Say if a coilpack or an injector , or single cyl. rings valves etc. bad ?? Get my drift , a warmup can affect and alleviatte the culprit , you can narrow down a cylinder .Maybe you try a set of new plugs ($60 ??) because splashed water or freak fluke can "crack porcelin" and you may have tried $$hundreds$$ of fixes.Outside of the new plugs this costs only "Time" !! My opinion is best "first attack " at your problem, Glen 2/10/2018

[brian300zx]

Also forgot to mention I’m getting horrible gas mileage. I’m getting about 150 miles on a full tank of city driving with a somewhat heavy foot but nothing crazy. I’ve read people getting anywhere from 200-250 which is why I’m saying the o2’s as well. My plugs are about a year old and I’ve only put 6k miles on the car in about a year

[macgiver]

mac again , O2's are operated open / closed loop .Open loop is startup to a pre-determined time-out and/or engine warmup plus adequate O2 warmup ( most O2's are electrically "heated") - during this time , they are OUT of the equation .Whearas your problem seems to be in this mode . After so much time that the O2's do come into play would seem to not be when your problem is at it's height - for it WILL take time to recover even after initiating "closed loop" (normal running -all sensors + O2's IN the equation) - as you say it becomes fine.
Next point is if your O2 test turns out Ok ,intermittantly ?? ,yet at one time showed in OBDII (i'm guessing)badly - the inspection of plugs can especially show that one BANK of cylinders is "off" and to go ahead and further check O2's (you have front&rears ea. side?) on a specific side ; but again if in closed loop you got a "greenlight" on the O2's for both banks ,you see how now O2' seem a distant possibility and a plug inspection , and I forgot to mention a very easily done COMPRESSION Chk. at this time . Just so you can avoid the jump to "shotgun approach" too soon(very expensive & no real logic either that way!!)
Respectfully Glen 2/10/18

[macgiver]

mac again , O2's are operated open / closed loop .Open loop is startup to a pre-determined time-out and/or engine warmup plus adequate O2 warmup ( most O2's are electrically "heated") - during this time , they are OUT of the equation .Whearas your problem seems to be in this mode . After so much time that the O2's do come into play would seem to not be when your problem is at it's height - for it WILL take time to recover even after initiating "closed loop" (normal running -all sensors + O2's IN the equation) - as you say it becomes fine.
Next point is if your O2 test turns out Ok ,intermittantly ?? ,yet at one time showed in OBDII (i'm guessing)badly - the inspection of plugs can especially show that one BANK of cylinders is "off" and to go ahead and further check O2's (you have front&rears ea. side?) on a specific side ; but again if in closed loop you got a "greenlight" on the O2's for both banks ,you see how now O2' seem a distant possibility and a plug inspection , and I forgot to mention a very easily done COMPRESSION Chk. at this time . Just so you can avoid the jump to "shotgun approach" too soon(very expensive & no real logic either that way!!)
Many different very serious problems do "clear up" after warmup ; coolant leak into cyl. onto a spkplug ,oil splattering(valve seals or rings) onto & fouling a plug - until they're hot and "burn-off" the oil ,head gasket losing seal - only to gain tightness after aluminum "expansion" closes up the problem , on, and,on and on!.Plugs wil help indicating this - even your new plugs - nobody is saying they were'nt replaced when you did ,it's just the FACT that all plugs do tell a STORY !!
Respectfully Glen 2/10/18

[echonightsi]

I too am having this problem. Although maybe a little different. I was thinking it was my cats, due to nasty smell until the car warms up and starts hauling a$$. Either way they have to be clogged at 190k. Do you notice a smell? Im replacing the cats sometime this week and will let you know if it worked or not.

[brian300zx]

I doubt it will be my cats honestly I’m pretty sure my cats are straight through at this point. I’ve had this problem ever since I got the car. But yeah my car is at 200k right now and I’m pretty sure the o2’s are still the original since they look really corroded.

[macgiver]

Cats can go well over 200k mi ,mine have 270k , and in my opinion from what I've learned - aside from corrosion due to very short trips ,winter snow/salt and such - a probable order of "Cat killer" is 1)fuel additives,you gotta make sure they say "safe for cat/emission" (even those are in a small way damaging) , 2)bad fuel ratio , yes as brianxxxx is trying to eliminate as a culprit his O2's,for they play a lead role,among other components ,3) blowby - bad rings,oil seals etc. -and oddly a bad choice of "oil supplements", which if do get "burned-off" through , out to the cat will be the"clogged" thing.But a kept up system , not going "nuts" with every additive out there (remember Arco Graphite? ) and they really can't assume a specific end of life.And we've heard of them being "extended warrantied" in some cases !Another reason to be completely sure of needing them replaced - being one of the most expensive emissions/running component.

[amc49]

Fuel additives indeed are cat killers and anything as well that bumps up the level of unburned fuel going through the cat. Why car makers warn against say running the cars out of gas and not to overfill the tanks, both of which can make the engines run too rich. I for one NEVER use any fuel maintenance chemicals of any kind ever and I used to sell thousands of gallons of them.

[brian300zx]

Same with me I have never used fuel additives even though they claim to help with mpg’s. My other option would be dirty injectors? Even though they read good they might be dirty/clogged? Being on the west coast I don’t have to worry about snow/salt so that’s easily eliminated for me. My car burns absolutely no oil stays on level until my next oil change. I’ve akways used Mobil 10-30 full synthetic which I’ve seen many people use. My best bet would be on my o2’s or dirty/clogged injectors