Bad O2 sensor? Ok to drive on? Cost effective solutions?

[SpeedDemon]

Hi all,

Tomorrow is the big So. Cal NSXPrime Canyon Drive, and suddenly I get hit with the following:

- The car's idle has gone bad. Idle is running lower than usual (700rpm), stuttering, often times will die when getting out of gear & coming to a stop, etc. (If it doesn't die when coming out of gear, it will "just" catch itself, and continue to run rough).

- Smoke from both tail pipes when idling. Ahh, the rich smell of gasoline! (Smoke looks very much like the thin wispy condensation vapor you'd see when you first start up in the morning by the way).

- Have had a few rough starts with regards to the engine catching -- cranking the engine/running the starter took much longer & engine was rough as it finally caught/started.

- Interestingly enough, the car runs fine in gear. Drives relatively normal if gears are quickly changed, seems to run fine under WOT even...

- No check engine lights so far!

That's all the symptoms. The dealer is indecisive w/o having a check engine light & told me to keep driving until something hopefully comes up (seems doubtful, I've been driving like this for 2 days now). They say they could blindly change the O2 sensors, but with a price quote of $280 for the rear primary O2 part (n/i labor), that could get costly fast if it's either the other O2 sensor (would have to buy both to find out!) or neither.

Questions:
1) How likely is it that it's one of my O2 sensors based on my symptoms?

2) Am I ok in driving the car for the 300+ mile NSX canyon drive tomorrow, including some of the aggressive driving that might take place?

3) Advice on the most cost effective way to deal with this? I'd guess people here could identify sources for O2 sensors where I could probably get both for the price the dealer wants for a single one! FYI, the dealer said that the front & rear primary O2's are different part numbers & aren't interchangeable, they claimed the sensor element might have a different length/depth front to rear.

Thanks much, especially if anyone can give me some speedy replies today!

Best,
Marc
97 NSX-T twin turbo

 

[len3.8]

Your o2 sensors are most likely still under warranty. With the turbo they may give some grief. But they are under an extended warranty from Acura. Call you dealer and see what options you have. With my SC they just replaced mine.

Search about o2 sensors there was someone with an issue a week or so ago. Look in the technical do-it your self section.
There is a link to the TSB
Len

 

[Briank]

Sounds like you have a fuel system problem, you need to check the fuel presure to the fuel injectors. The fuel presure regulation system which for the SC is modified from stock to provide additional presure / fuel to meet the needs of the engine under boost. Looks like you are running at higher then needed presure at low speed.

 

[Elite]

you will also want to check for boost leaks.

 

[DutchBlackNsx]

The NSX O2 sensors are known to fail after 10 years or so, but what normally goes on them is the internal heater, and not the O2 sensor itself. If the heater goes, the 'check engine' light comes on for sure, since this is easily to see for th ECU.
Driveability is not affected, and there is no real danger in driving without the heater.
But thats for a NA only, if this is FI, then i wouldn't take a risk if there is is a problem with fuel management in ANY way.

 

[Klas]

DutchBlackNsx: I got my ‘check engine’ light lid up yesterday at the track with code 42 = Rear HO2S Heater.
My mechanic says it’s the O2 that’s gone bad and the engine run in with preset values witch is rich and potentially can damage the cats if I drive to long and to hard.

When the subject is up, is it possible to change the rear O2 with normal tools, is there any DIY on this?

 

[sjs]

The idle symptoms are severe enough to worry me because it sounds rich enough to damage not only the cats but perhaps also the rings/cylinder walls. The good news is that if it was known to be an O2 sensor issue then is only applies in closed loop so it would still be fine when driven hard. But the reality is that even during an aggressive street outing you are in closed loop mode quite a lot, so I would question the wisdom of doing the Canyon Drive. Not what you wanted to hear of course.

Some of the symptoms are similar to a "boost leak", or more accurately a vacuum leak in this case, but that seems unlikely if in fact it is also running very rich.

Overall I'm inclined to suspect an O2 sensor but there is no guarantee. One way to test it, though it requires a bit of messing with the wiring, is to split the output of one sensor to feed both, then swap the other way. Perfectly legit with the only problem being that all cylinders are trimmed according to the output of only three, but that's no big deal if all are reasonably similar and certainly adequate for testing. If that fixes it, go on your canyon run and enjoy.

 

[sjs]

...But thats for a NA only, if this is FI, then i wouldn't take a risk if there is is a problem with fuel management in ANY way.

Although I agree with the last part, if this is an O2 sensor issue then it is no different for a turbo or SC car than a stock one because the sensors are out of the loop and doing nothing long before boost.

 

[Larry Bastanza]

Hi Marc,

Since you mentioned in the beginning the idle is "rough" have you checked the plugs and coils? Since this is an ODBII car it will normally give you a rich/lean O2 code if it is an 02 sensor. Actually I find it very strange you do not have a ECL. Maybe a spark plug? The coils are also checked by the ODBII system to insure that they are firing correctly.

Oh, Are you running a standard ECU, or a AEM, Motec etc??

Anyway, just a thought. If in general your setup is a little on the rich side, a fouled plug is not out of the question.

HTH,
LarryB

 

[BadCarma]

I agree with SJS's assessment. also pull off your intake and look behind the butterfly on the throttle body and check if it is gunked up with any sludge,this could cause the rough low idle if you are getting heavy blowby. do you use a catch can?

I dont think it would account for the heavy rich condition you mentioned (thick gas smell unless you run straight pipes) also I would think if you were running that rich you would be throwing a code already. pull the codes yourself:

http://www.nsxprime.com/FAQ/DIY/trouble_codes.htm

if it was mine I would:
retreive codes
check throttle body for sludge
poke around for vacuum leaks ,doubtful if running rich but check anyway. also I would check the fuel pressure at the service port on the fuel filter.B&M makes a gauge for honda's with the correct adapter to access pressure at the filter.
these are all very easy to do and will take about 30 minutes, more if you check pressure, it cant hurt. I would not drive it at all until resolved in case you are running super rich and the potential for aggravating the problem or damage,lastly remember we often fear the worst and it could be minor but dont take any chances

let us know what you find out when you do resolve the problem and if it does turn out to be 02 sensors checking the throttle body is worth the time as well as pressure anyway

best regards david
PS larry posted while I was writing,checking the plugs and coils is a good idea as well

 

[sjs]

...Since this is an ODBII car it will normally give you a rich/lean O2 code if it is an 02 sensor.

Good point. I make the mistake of thing OBDI like mine which can run very rich without it complaining, but with the OBDII I'm surprised it can run that badly without some kind of code.


BTW, the dealer's recommendation sounds irresponsible at best.

 

[SpeedDemon]

Hi,

Just wanted to thank everyone so much for all the great advice.

The problem was not the O2 sensors, and I never did get a check engine light. I can't comment right now on what it was, except to say that it relates to too much fuel getting into the cylinders due to mechanical causes (ie, leaky injectors, etc) and not from anything electronic/management related (like ECU or O2 sensors). I'll explain more eventually when I can!

Thanks again to everyone that responded!

Best,
Marc

 

[sjs]

Oh sure, leave us in suspense!

Wow, that rich and didn't throw a code. Might think about that later.

Well, hope you mad the drive!

 

[Larry Bastanza]

Yes, But Marc did not answer my quesiton about the actual fuel management in use. Maybe there are no codes to get!!

mmm............................



LarryB

 

[SpeedDemon]

>Yes, But Marc did not answer my quesiton about the actual fuel
>management in use. Maybe there are no codes to get!!

Ooops .

I'm running with the stock 97 factory ECU.

I think it's an important point to note that the stock ECU will apparently not throw a code if you're not running well at idle unless a component it checks for is failing (rather than looking at how you are running...) At least in my case, anyways.

Best,
Marc

 

[Larry Bastanza]

OK, Now we are in COMPLETE suspense.

How was the Canyon Run??

LarryB