I just took the car (99 355 F1) for a smog test and it failed the 15 MPH rest with NO at 776PPM. The 25 MPH passed with 280 PPM. The last test was just six months ago and 1,000 miles. It passed easily then. Would a bad O2 sensor cause this and shouldn't that set a light? I have never had a Check Engine light. Which side is the number one bank from the rear of the car looking forward?
I would get an OBDII reading on it and check to see what codes come up for a proper diagnosis. I'm lucky living in the state of Pennsylvania, as I'm emissions exempt as long as I put less than 5,000 miles per year. I'm lucky that each year they keep slapping an emissions sticker on my F355 with the tubi exhaust and test pipes. California I know is a different story.
What was your HC level during the failed NO? Also, which side did they test last time?? a scanned copy would help.
Today= %CO2 14.2, %O2 0.6, HC (PPM) 18, CO% 0.02, NO (PPM) 776 6 months and 1,000 miles ago %CO2 14.6, %O2 0.0, HC (PPM) 12, CO% 0.03, NO (PPM) 109 The only real change is the NO readings, from 109 to 776 in the 15 MPH test. 424 is passing The 25 MPH test passed with the NO readings at 280. 711 is passing for 25 MPH I'm going to try to get the ODB2 scanner on it tomorrow and see if there are any codes.
Is there a way of checking the air injection at the manifolds. There is a valve cap there, can it be checked with a pressure gauge? if so, what should the pressure be?
Hmmm, I always thought HC and NOx values moved inversely to each other. That is, high HC is supposed to be a possible rich condition and high NOx is supposed to be a possible lean condition. Don't know where I originally got this info, just repeating it in the event it corroborates any of the other information you obtain. Good luck!
I can think of a bunch of things which could cause problems some cheap and some expensive. But in this case it really looks like high NOx and the Hc is fine. Most diy'er don't have tools like the pros so you gotta take potshots at likely candidates. I'd be looking for obvious vac leaks. Throw an obd2 testor on there to get some clues. You can have pending codes that do not show on the mil as an example. You can also read more than just codes on better testors. Scope the engine to see what the electronics were doing like looking for misfires. All that stuff can be done for a few hundred bucks in meters and such. Or some smog shops or even the local gas station usually have the equipment to scope the engine for the $50 buck range and 15mins of time. I don't know what the 355 has for an EGR system but looking in that direction is a good idea to. Failing EGR sytem can wreck NOx output. Lets hope for cheap easy stuff.
I just smogged my 1999 F355. Passed very good. I took her to the 76 station in Belmont. It's at the intersection of Ralston & Old county Rd. Guy named Norm. Knows his stuff. Not sure where in the bay area you are but sometimes a second opinion is worth it. Good luck.
One big change you have overlooked is the increase in 02%. In an OBDII car, an increaase from 0.0 to 0.6 is massive. You aren't getting a good burn from either the cat, or something else. How cold was the car? What octane gas are you running? If I were you, I would go out and pound on the car with at least 94 octane in the tank and get the thing good and hot. Then pull it right into the smog test and you'll probably pass. NO is not your problem right now, it is the presence of too much O2, which in turn in pushing your HC and NO numbers up slightly. you aren't that far away from passing. Definitely get the octane up to 94 via boost or better yet, a few gallons of 100 octane. And then keep it at 94. People who run 91 here in CA in their F355's are not doing it any favors in the least.
Pre cat readings, there are ports provided will really help pinpoint your concern. NO is caused by high combustion chamber temperatures. Generally lean conditions cause this but ignition timing, camshaft timing and catalyst concerns plus anything causing engnie to run hot are all items that need to be looked into.
OK, here's what happened today, I used electrical cleaner on the connectors, but not the sensors themselves, put it all back together and took it to the smog guy Michael suggested. (BTW, a really nice guy, thanks Michael) Now there are two different codes. P0131 and P0137, Both passenger side O2 sensors have low voltage! I've ordered two more sensors but they won't be here until Wednesday. I'd really appreciate any help on this as the car is sold and I can't deliver it until it's smoged.
I am always leary of new codes that pop up especially when you have done something. That code could be the 02 sensors themselves or the wiring to them. First thing I would think of is to take the connectors apart again. Clean them again on the sensor and the car side and let dry or blow out with compressed air. I would bend the pins of the connectors to ensure good contact. Then I would erase the codes and see if they come back. Also, this new issue once resolved may still not solve the old no pass condition.
I've had the connectors apart several times, they look good. I'm not worried about having two more O2 sensors if that doesn't fix the problem because they're the same as the 550. Thing is I don't know what voltage I should have on which wires in the car side of the connectors. Shouldn't I have some heater voltage on some pins?
Yes heater is ground and 12V+ so O2 sensor does not have to rely on engine heat alone to get into closed loop function. With most DIGITAL VOM's you can back probe the trigger wire (while engine running up to temp in closed loop) and look for fluctuating voltage say around 0.2-0.8V. Low voltage hanging can imply bad sensor or real problem upstream like Vac leak which would also spike your NOx because lean mixtures are hot and hot=more NOx. This code could be a coincidence or really be something.
I replaced both right side O2 sensors, passed with flying colors. Nox went from 776 down to 77 Now I just have to round up everything that goes with it and deliver it to it's new owner. Kinda sad to see it go after twelve and a half years but it's time to move on.
Thanks for posting the solution. Always nice to have an answer like this filed away for future searches.
NOx is produced when cylinder to temperatures reach 2500° the egr system dilutes the air charge to lower cylinder temperatures if your co and hc reading are some what good and the NOx is going out of range at 15 mph but gets better at higher speeds you will need a scan tool to check short and long term fuel trims and also check the egr system possible that one bank is not getting efficient flow of exhaust gas at lower road speeds Sent from my iPhone using FerrariChat.com mobile app
try getting your exhaust hotter take it for a good hi way rip and then get to the smog shop Or you could wrap your cats that is if they are like hi flows If they are stock it will still help. If it does not pass in my experience the post o2 sensor is giving problems. you could also look at your fuel trims to make sure nothing is major wrong
