O2 sensor PROBLEMS

[poweroptions]

Our Q45 keeps showing code 138. The O2 was replaced with a replacement I ordered from Sparkplugs.com, it was OE replacement. In the last 9000miles the SES comes on at any given time. Car went to Infiniti where they reprogrammed the ECU. Worked for the first 1000 miles now SES is on code 138 again.. Went to Infiniti this morning now they are saying I need to replace both O2s on that bank. Infiniti service is telling me the NGK O2 is not the same as theirs out of their parts dept. IS THIS TRUE? They said $600 for both.
Modified by poweroptions at 8:22 PM 5/30/2008

[Q45tech]

Pretty near impossible to buy oem parts except at dealership. Some companies/ebay sell overstocks, stolen, highjacks, or Chinese copies...........just like Rolexes.

NGK often sell functional equivalents or just generics to aftermarket discounters.

Well dealers warranty their parts/labor for 12/12k that will tell you if the O2 are indentical if the codes stop in 1000 vs generic NGK.

[maxnix]

The NTK sensors on http://www.sparkplugs.com were not correctly specified on the served web page when we bought ours a couple of years ago. Had to call to obtain the correct ones.

Joe will have the OEM ones.

http://www.infinitipartsusa.com

[poweroptions]

No the dealership hedged on a warranty yesterday when I asked what they would do that if in 1000 miles the SES 138 reoccurred. The senior service rep said, " well it could be a couple of more possibilities, ex: bad ecu, a clogged catalytic converter, and something else with the cat converter, all would need to be replaced." OK thats scaring me. I didn't feel like gamb|ing the $600 on a questionable fix. I picked it up last night and returned the 08 G35 they lent me. I see Maxnix has maybe the answer. I assumed the Sparkplugs replacement was pretty much the same as the OEM. They looked the same to me. Grrrr I wish I had the right fix.

[poweroptions]

Thanks Maxnix for the advice! I'd really like not to see the SES on. I hardly think the cat converter is plugged or the ecu is bad. The dealership themselves tell me our Q is one of 3 of the nicest of this vintage in the Dallas area they service. This is the 3rd trip to Sewell Infiniti and I got the feeling they didn't really know why the damn code comes up. Like I say thanks for Joes address, I really want to get this right.

[maxnix]

Well, most of the difference is in connections and perhaps mounting depth of the sensor.

i am sure Sewwll is nice, but what it really takes is an experienced Senior Infiniti Tech, in your case someone who was senior and traind on the VH41DE in 1996. With OBD II and experienced analysis of Consult II readouts, problems should be narrowed down to a couple of secenarios.

Clogged converters are pretty easy to determine for a dealer.

[poweroptions]

I need a knowledgeable mechanic in east texas, living out here in the country driving back and forth to Dallas for repairs for something minor like this is driving me nuts. Would you think replacing both O2 on that bank is the answer? All my other cars are mechanical not computer operated, I don't have a frickin problem with any of them. Our rolling whorehouse (78 TownCar, blk/red velvet) gets nearly equal mileage to the Q, 16MPG verses 19MPG.

[maxnix]

Hmmmm.....that's about 20% difference.

O2 sensors are best replaced in pairs. this has to do with the duty cycle of a new vs. and older one. Once again, this applies particularly to primary sensors.

none of the injectors have been removed, have they? And they do ohm test correctly? Ever used BG44K? No ethanol in your gas yet, I trust? there is in Dallas and Houston, I know.

[bullittandy]

It seems very unlikely to me that the original O2 sensors caused a code and then a replacement se of O2 sensors caused the SAME code.

I would not replace the rear O2 sensors (especially for $600!!!!!!, parts are $50 and labor is 1 hour at most!!), I think that the rears were "universal" as compared to th front when I bought my last set. NGK is reputable brand and so for now assume that the problem is elsewhere.

I would replace the front O2 sensors since they are probably due and see what happens next. As long as you don't have any drivability problems you can be patient-unless you're like me and hate the light!!

I just saw your other post about the idle miss, replace the bad coil and you lose that light I think.

Now how to find the coil? Nobody knows without a OBD code and they don't appear to trip with a bad coil. Nobody knows how to find one so.......

[poweroptions]

To my knowledge it is ALL original I bought this Q with 33,000 miles and all Infiniti Store service records that showed no repairs of anykind. I did the gas Treatment BG44K. It ran great with it. After 2 or 3 tanks the SES was on again. The stumble I had felt at idle ceased when Infiniti reprogrammed the car. I only have premium fuel with 10%-15% ethanol available. There is nothing else . It does drive me wack to have a warning light on , on the dash. I drive all my old cars of my lifetime and none of my others have warning lights on , if they did, it would get fixed. Well I'm fricking blue collar and $600 was not going to happen. I compared the NGK rear I replaced to the original Infiniti and it all was identical on the outside including wires and clip harness. None of the injectors, nothing beens screwed with or changed. The Q is ran to DFWairport/ doctor appt,out of town road car. No stop and go, mostly hwy. So NEXT step is for me to replace the front O2 ? Right?? NGK or should I step up to Joes @ Infinitiparts for twice as much$ TYall

[bullittandy]

Re-read my post. Replace the front O2 sensors because they are wear items and need to be replaced anyway (like an airfilter) and so even if it doesn't knock out the light you haven't wasted money.

The idle miss is a bad coil-I don't know how to find which one (out of 8) is bad without a check engine light so.......

[poweroptions]

Got it, ordering front O2 and at least one new coil. Light had been out for 195 miles since bringing it home. I pulled up to a stop at my gate, getting out of the car I felt the shake in the body glanced at the SES and its was on.

[maxnix]

Good. Now you have a code. See which cylinder is misfiring (hopefully only one). Switch that coilpack with a known good one. Clear the codes. Whenit happens again, see if the code followed the coilpack or or reamined at the same cylinder. if it remained, you nedd to discover if it is injector, plug, or ?

I agree with Andy's recommended triage. But if the rear O2 sensors are bad by test (not just OBD II codes), then you will have to replace them also.

[bullittandy]

Got it, ordering front O2 and at least one new coil. Light had been out for 195 miles since bringing it home. I pulled up to a stop at my gate, getting out of the car I felt the shake in the body glanced at the SES and its was on.

I am having the exact same problem right now with my 99. Occasional idle stumble and today for the first time it stumbled through the rev range. The problem I'm having is that it is not tripping the SES/CEL light and so there is no easy way to find the bad coil.

Please, does anybody have a way to test a coil?

[maxnix]

EC-399 in the 2000 FSM is the only reference. You'll need a scope.

If it's misfiring, it has to be throwing a code. Are your KS and harness good?

[lakeq45]

Sounds almost exactly like what I went through on my '01. There are posts about it in at least a couple threads. In my case ended up requiring a new ECM, under the 80K warranty thankfully. You can move the "bad" O2 sensor, if it is really bad the code will move too.

I paid for the initial "bad" sensor and labor, just under 400 if my memory serves (I'm too lazy to go dig through the records). This was followed by a lot of repeat visits while the techs traced the actually problem. Probably took longer then it should have, but they didn't charge me for their guesses.

[poweroptions]

Doesn't someone on here rebuild ECMs? My Q went throwing this O2 code just as the 8yr wrty ran out at 41,000 Oct.07, it's been nothing but to the shop with the SES on, it's now May 08 and Q just turned 50,000. Aggravates me and it hasn't shown a code for missfire. Those ECM are $$$$ hope it isn't the problem

[maxnix]

Well, you could take your chances with a used known good ECM.

Not rebuildable, unfortuantely.

[poweroptions]

I didn't think I'd be having problems like this with this car. I have parts coming but I am unassure if this is the right fix. Distressing to know Infiniti is just as unassure. At 50K I thought I'd have smooth sailing in a Q. Tonight the steering wheel is vibrating when I step on the brakes. I assume this is warped rotors NOW. I was looking at drilled slotted replacments with ceramic pads. Anyone have an opinion???

[maxnix]

Get the Stillen Brembo rotors from Joe with OEM pads.

He might be running a special very soon, right Joe?

I really doubt the ECU cause, but a quick switch with another known good one will tell.

[poweroptions]

I don't see a sale posted yet. Is there a "sale" area I missed?? I was right in new rotors and pads since it just started vibrating when I brake?? I can apply harder brake pressure and there isn't the thrashing steering wheel. I need to go shake that money tree, o2s, coils, brakes.