emissions testing showed NO too high.
Yeah I learned my lesson for smog with the above problems. I've got a bit of breathing space when it comes to HC and CO since they were pretty low. Just gotta pretest until I find that magic middle point between all 3 and hopefully pass my smog check. When I do indeed pass I'll keep you posted and tell you the final numbers.
Alrighty, old thread, same problem. I went back for another smog check the other day to see if I'd finally pass with a new cat and a new o2. Failed again. Here are the readings.
15mph:rpm = 1717%co2 = 14.2%o2 = 1.3HC (PPM) = 11CO (%) = 0.00NO = 1356 <---Fail
25mph:rpm = 1748%co2 = 14.4%02 = 1.1HC (PPM) = 6CO (%) = 0.00NO (PPM) = 1074 <--- Fail
So now that I've eliminated the cat and the o2 as possible culprits, the focus goes back to the EGR. I was told by the smog technician that the EGR does function, but it doesn't open up all the way. It just blips open. The other possibility he said was that I've got carbon deposits on the walls of my cylinders that's insulating the cylinders thus keeping the temp high.
I'm planning on getting a new muffler with just a 1" opening to see if that'll help out the situation to keep some of that backpressure around. That's the kind of muffler my car had when I bought it and it passed back then. So that's a possibility.
The other possibility is that perhaps my egr needs cleaning? Other thing is how would I go about cleaning the carbon deposits off my cylinder walls? My car has 175,875 miles on it now and that's a possibility.
The other thing the guy told me that stands out is when he asked me how accurate the afc's air flow reading was. He said that the air flow was around 10% and that I should try to raise it up to 14%.
Any ideas on what I could do?
15mph:rpm = 1717%co2 = 14.2%o2 = 1.3HC (PPM) = 11CO (%) = 0.00NO = 1356 <---Fail
25mph:rpm = 1748%co2 = 14.4%02 = 1.1HC (PPM) = 6CO (%) = 0.00NO (PPM) = 1074 <--- Fail
So now that I've eliminated the cat and the o2 as possible culprits, the focus goes back to the EGR. I was told by the smog technician that the EGR does function, but it doesn't open up all the way. It just blips open. The other possibility he said was that I've got carbon deposits on the walls of my cylinders that's insulating the cylinders thus keeping the temp high.
I'm planning on getting a new muffler with just a 1" opening to see if that'll help out the situation to keep some of that backpressure around. That's the kind of muffler my car had when I bought it and it passed back then. So that's a possibility.
The other possibility is that perhaps my egr needs cleaning? Other thing is how would I go about cleaning the carbon deposits off my cylinder walls? My car has 175,875 miles on it now and that's a possibility.
The other thing the guy told me that stands out is when he asked me how accurate the afc's air flow reading was. He said that the air flow was around 10% and that I should try to raise it up to 14%.
Any ideas on what I could do?
richen it up. all your readings indicate your running lean. he may be correct about bumping it to 14. I am not familer with your device but i believe he is saying you want it to show its recieving more air which would tell the computer you need more fuel. this will help cool the cyl. even then you may still have an egr problem. but your egr will fluter like that if it is not under load. the back pressure wont maintian if its not under load.
Ok well I had the car running at 0% change in the AFC's settings. So I should richen it up to get the cylinder's temperatures down. ok got it. With the air flow, I'm not sure how to change that. The AFC only tells me how much air flow is flowing and doesn't physically change that. Only thing I can really do with the AFC is modify the fuel maps by tricking the ecu. So come around next smog check, I'll richen it up more in that 1k-2k rpm range and see if there are any improvements. Also, how can one tell by those numbers that you're running lean?
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Chuck Hanlon
- Posts: 86
- Joined: Fri Feb 20, 2004 4:40 pm
- Car: road racing, drags, camping, fishing, grandkids
15mph:rpm = 1717%co2 = 14.2 [generated by the burn and cat function this indicates efficency of burn]%o2 = 1.3 [oxygen content leaving exhaust indicates its a little lean, should be less then .5]HC (PPM) = 11 [amount of raw unburnt fuel this is really good but if it gets up around 100 it indicates miss fire]CO (%) = 0.00 [ amount of partially burnt fuel. this number should be slightly higher at its present level indicates it does not have enough fuel ]NO = 1356 <---Fail [ fused nitrogen to oxygen created by heat and pressure] The temp in your cyl will rise when less fuel is present the pressure already exists. Although readings like yours indicate there may be more then just that.
25mph:rpm = 1748%co2 = 14.4%02 = 1.1HC (PPM) = 6CO (%) = 0.00NO (PPM) = 1074 <--- Fail
HC and CO go hand in hand in most cases if a failure were to have high HC and low CO it indicates it is extreamly lean and is most likely missfiringand will fail for NOx in the 2000 range. On the other side If CO was high and HC was very high it would indicate a rich condition. the NOx in this case would be very low in the 100 or even lower range.
same holds true for 25mph readings. although your HC and CO readings are very good and your car would pass the TSI test it will not pass the ASM test you are having done. You have to be careful when you richen it though as your CO and HC will rise with the adjustment so you need to do it in small steps. The carbon in the cyl theroy is still possible. What happens in that situation is carbon will build up in the head around the valves. This does 2 things 1] it makes the cyl smaller which increases pressure. This can be checked with a compression tester. If the pressure is substantially higher then the standard spec then you most likely have build up. 2] the carbon gets hot and retains heat in many cases you might hear pinging [preignition] due to the heat from the carbon igniting the fuel before the plug fires. This theroy though on nissans is rare, so rare I have never seen it or heard of it on one.
You have a point as well with your back pressure in your exhuast for egr operation. you need to be sure its there. best way to make sure is to hook up a vaccum gauge teed in between the BPT and the EGR then place the vaccum gauge so you can see it while driving. watch it on mild accel from a stop or while cruising down the freeway. it should come up and hold about 5 in of vaccum under maintained light accel.
25mph:rpm = 1748%co2 = 14.4%02 = 1.1HC (PPM) = 6CO (%) = 0.00NO (PPM) = 1074 <--- Fail
HC and CO go hand in hand in most cases if a failure were to have high HC and low CO it indicates it is extreamly lean and is most likely missfiringand will fail for NOx in the 2000 range. On the other side If CO was high and HC was very high it would indicate a rich condition. the NOx in this case would be very low in the 100 or even lower range.
same holds true for 25mph readings. although your HC and CO readings are very good and your car would pass the TSI test it will not pass the ASM test you are having done. You have to be careful when you richen it though as your CO and HC will rise with the adjustment so you need to do it in small steps. The carbon in the cyl theroy is still possible. What happens in that situation is carbon will build up in the head around the valves. This does 2 things 1] it makes the cyl smaller which increases pressure. This can be checked with a compression tester. If the pressure is substantially higher then the standard spec then you most likely have build up. 2] the carbon gets hot and retains heat in many cases you might hear pinging [preignition] due to the heat from the carbon igniting the fuel before the plug fires. This theroy though on nissans is rare, so rare I have never seen it or heard of it on one.
You have a point as well with your back pressure in your exhuast for egr operation. you need to be sure its there. best way to make sure is to hook up a vaccum gauge teed in between the BPT and the EGR then place the vaccum gauge so you can see it while driving. watch it on mild accel from a stop or while cruising down the freeway. it should come up and hold about 5 in of vaccum under maintained light accel.
right on. thanks for that info. I'll have a look at the vac pressure from the bpt and the egr to see what's cooking down there. I'll post my results when I have access to my tools this weekend. Thanks again for the help, it's very greatly appreciated.
Yeah apparently the guy I bought the car from bought a 26.00 muffler. Yes $26.00. That would explain why it rusted apart in about a year and also had the very small opening. I'm counting on that to help me get some more backpressure. lol *cries at the same time*
Yeah apparently the guy I bought the car from bought a 26.00 muffler. Yes $26.00. That would explain why it rusted apart in about a year and also had the very small opening. I'm counting on that to help me get some more backpressure. lol *cries at the same time*
Alrighty, so I've got the old muffler coming in from a friend who's donating it for this cause. However, I'm still a bit paranoid about the EGR. So I assume I've gotta pull the egr off the head and then start to hose it down with carb cleaner huh? Any recommendations on how to get the sucker off? It's in there pretty deep.
it is a task be patient and think it through logically before you start ripping parts off to get to it. Find the easiest road before you put any tools to bolts. It is a bear to get out but if you think it through first it will be a breeze. I dont know the exact step by step process but if you remove the BPT and its bracket it does make it easier.