Hi, I've chasing a bit of misfiring when the engine is warming up. I've done a lot of work making sure everything is working and now I've come to the O2 sensors. From conzult, the RH one seems to move a lot slower than the LH side. It never goes out of limits but it just goes from rich to lean slower than the other. The problem is, how do you confirm it's the O2 sensor. If there was a problem with the RH side of the engine, wouldn't that cause the same thing? I'm leaning towards the O2 sensor though as I don't believe they have ever been replaced - 140k kms. Cheers, Matt
It's slow when warm>>> After holding the revs at 2000rpm when hot that is, like the test is supposed to be done. I'm just not sure they would affect the car when it's cold because I believe that the feedback value in the ecu determines the temp that the ecu starts to look at the o2 values. Mine is set at 75 which means that at 50 degrees C it takes readings from the o2 sensors. I can't see what else would affect it when cold. I've checked the idle control valves, air regulator, no air leaks, replaced spark plugs, ecu coolant temp sensor gives correct readings....not sure what else to check. Cheers, Matt
Re: It's slow when warm>>> If its still slow when its warm. Then the O2 is stuffed. If your quick you can get a new pair on the group buy.
Define 'warm'. Really need at least 80 degrees+ to get best feedback/assessment from 02's... A hard run on boost over 10 minutes on a warm day should suffice... then test... I've seen 02's that appeared : * 'dead' @ 69[sup]0[/sup], * 'lazy' at 75[sup]0[/sup], * almost perfect @ 80+[sup]0[/sup]
if they dont work at startup they are stuffed The 300zx O2's have internal heaters and will work properly from startup. The bizzo about the car needing to be warm for them to work is not right. In old cars that had single wire O2's the car had to be at operating temp for them to work. Not ours If they dont fluctuate from the car starting cold, they are basically stuffed. The ECU on the other hand will not use them to adjust mixture until the car is off the choke and warmed up. If they are lazy until the car is warmed up they should be changed.
Hmm. Well, I recently put brand new genuine ones in and they are lazy until the car starts to warm up?
I understand what you are saying Graham, but I have experienced this phenomenon of 'lazy-when-cold, ok-when-hot' on at least 50+ zeds in the last 12 months. I agree that if they are lazy when properly hot then they need to be replaced at some stage but I think people are often too trigger-happy to write off an 02 just because it appears a bit lazy on consult/datascan. My RHS 02 is 99% dead and yet I still get 400K+ b4 fuel light and have superb acceleration on stock boost :thumbsup:
Having said all that I have one of those in the car myself. The interesting thing that happened to me is that I Consulted the car and one O2 didnt move till it got warm and I figured it needed replacing. I didnt do it for ages as I was tied up with other stuff. Anyway, I tested it again a while ago and the bastard is now working great from cold to hot. Makes me wonder if external issues like lots of WOT running and the richness that zeds do from stock at WOT tends to stuff these bastards up. And then it takes a while to burn the crud back off em so they work again. I would bet that on a well tuned car the O2's work much better. Stock tuning isngt helping them I dont think.
O2 sensors only start to work at around 300 degrees >> Zirconia Oxygen Sensors are made from a ceramic that is known as zirconium oxide (ZrO2). This oxide is selected for use in the automotive industry for its outstanding properties such as, high flexure and tensile strength, high fracture toughness, high resistance to wear and corrosion, low thermal conductivity, and oxygen ion conductivity. Zirconium dioxide along with platinum electrodes and a heater make up the major current internal components of the zirconia oxygen sensor. Because the zircon dioxide ceramics material becomes conductive from about 300° C for oxygen ions, an electric voltage develops with differing oxygen content between outer and inner electrode of maximum 1 V, which is picked off via the cable terminals. The lowest amount of nitrous oxide (NOx), carbon monoxide (CO) and hydrocarbons (HC) are created when the air/fuel mixture is a perfectly balanced aka "stoichiometric" fuel mixture of 14.7 parts of air to 1 part of fuel. The zirconia oxygen sensor at this 14.7:1 mixture generates a nominal voltage of 0.45 volts. The zirconia oxygen sensor's output voltage does not remain constant but rather varies between 0.0 volts and 1.1 volts depending on manufacture.
a non Z specific article says for the heater lines to be turned on the engine to be running for a certain amount of time, (probably in the seconds), coolant temp to be above 32 degrees and when air flow is below a given point. The signal is ignored during engine starting, during cold engine operation, during heavy to moderate engine load, during accelerating and decelerating I can confirm this with my dodgy O2's in that it takes about a minute before it starts running like shit.
I think you're right Mark K-zed found my RH O2 to be lazy at the dyno day. However I tested it again last weekend and it appears to be ok again. The little buggers have got a mind of their own:wacko:
Teky, that's not quite correct. The O2 sensors may react when the engine is cold, but the ecu will ignore the signals. It's the constant closed loop feedback between the O2 sensors and the ECU which causes the signals to fluctuate. The regular fluctuation of the O2 sensor readings is due to the O2 sensor saying that the mixture is eg rich, which causes the ecu to lean the mixture off, then the O2 sensor reports that the mixture is lean, so the ECU richens it up, the O2 sensor reports that the mixture is rich, so the ecu leans it off, and so on. If the ECU is ignoring to O2 sensors, then the output voltage of the O2 sensor may vary according to how much oxygen is in the exhaust, but it will not vary regularly like it will when the ecu is using O2 sensor readings to fine tune the engine. The inbuilt electric heater in the Zed O2 sensors (and others (commonly called 'three wire sensors')helps to bring the O2 sensor up to operating temperature sooner, keeps it within its operating temperature during warm running, and also helps to keep it clean. O2 sensors will tend to clog up and be sluggish or not respond at all if the car is driven slowly eg in heavy traffic or the mixture is overly rich or the exhaust gas has oil in it, some fuel additives, etc. Taking the car for a highway speed drive helps to burn deposits off the O2 sensors. For this reason it's always a good idea to check O2 sensors straight after a highway drive, or a 'spirited' drive (or two) around the block. 4CE FED, having said all that, 140,000 km is a bit much to ask of an O2 sensor, so replacement would be a good precaution. I doubt that your misfire while warming up is due to O2 sensors though. Have you tried using ConZult to tell the ecu that the coolant is hotter than what it actually is, to see if this changes your misfire? Just thinking it might still be your temperature sender, maybe allowing the mixture to be too rich while warming up? Good luck tracing the misfire :zlove:
I'll give it a try But i've watched with conzult and the temp seems to be fine. Starts off around 20 C then gradually gets up to 80 C when the right temp. You're right, I wouldn't think the o2 sensors would affect it during warm up. I'm just unsure what else could be causing the problem. I took the air regulator off yesterday and took it to pieces, cleaned it and put it back on. Also blasted carby cleaner thru the idle control valve, it all seems fine. Cheers, Matt
Didnt I say that earlier about the O2's not working when its cold???? The sensors only work at idle and in closed loop. WOT running in open loop use the Fuel map to inject at a preset amount of fuel for the load. I understand how they work to keep the car stoic So my point is. If you hammer the shit out of it at WOT, or continually floor it in traffic. The car is running in open loop a hell of a lot. That is a very rich state. I was making the point that it could clog up your O2 sensor if you run for prolonged periods in open loop. (like on the auto bahn) Your points about the heaters are valid, and basically what i said. Cool The overriding point I was making about the O2's is that they can clog up if the car is running too rich. Here is a Fuel map from an NA. See how the map values in closed loop are almost the same in each cell. [/URL] The blue area is closed loop and means that the O2's are being used to adjust the mixture. The top axis is throttle position and the left axis is revs. See how at idle the car is always in closed loop. So idling in traffic is one of the best situations for emmisions. But have a look what happens when you floor it. The car goes into open loop and uses the table to instruct the ECU to shove in the right amount of fuel. At this point I can say most Zeds run rich. Its because the open loop portion of the maps are too safe and enriched. This is why I think the O2's can be clogged at WOT. The car is blubberingly rich at these time. If you drive like a nanny. You can see the car is efficent if the O2's are good. We are at one Dangerous :LOL::LOL::LOL:
