Failed Emissions Again
11-19-2007, 01:02 PM
#21
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no oil burn!! at all compression is SPOT on! ( to my suprise) im running the out of it before the test its a 1/2 mile off the highway so cat is hot o2 is good checking timiing tomorrow just to make sure but man! this thing runs like a beast and the gas mileage is getting better and better but the readings keep getting worse
11-19-2007, 02:22 PM
#23
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Have you tested with it not real hot, just warmed up? I seem to remember something about NO being produced more at very hot temps. It must be running lean to be have such good MPG and a lean engine can run very hot, like melting valves and pistons hot. Maybe you're running too lean from a bad O2 sensor or something.
11-19-2007, 03:09 PM
#25
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The 5w30 was running a little thin I had to add about a qrt. between changes I put in the 10w30 and it was'nt loosing as much... now that I'm running the Engine Restorer stuff at each change as well I might tyr the 5w30 again but this engine has 315K on it and the thicker oil might still be better... we'll see what happens...
You have something else going on here.
Fred
11-19-2007, 03:28 PM
#27
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My memory was correct, cylinder temps too hot cause more NO.
http://findarticles.com/p/articles/m...9/ai_n15353730
Might try testing it with a cooler engine temp
I'll quote them here since the pop ups are so bad in that link:
http://findarticles.com/p/articles/m...9/ai_n15353730
Might try testing it with a cooler engine temp
I'll quote them here since the pop ups are so bad in that link:
First off, Dan, I believe the article you're referring to is actually three Driveability Corner columns written by Mark Warren. The first appeared in the April 2003 issue, and was followed by February and April of 2004. While the columns did deal with a driveability problem on a Jeep 4.OL, the problem was entirely different from what your customer is experiencing.
Second, a lack of backpressure caused by the aftermarket exhaust system should not cause an increase in NO^sub x^, at least not on a vehicle that's capable of adjusting its own air/fuel ratio. Let's consider the things that can cause NO^sub x^ to increase to an abnormally high level. Oxides of nitrogen (NO^sub x^) are formed when the combustion chamber temperature exceeds 2500°F (the ignition point for compressed nitrogen). The engine must normally be under some kind of load before it develops such high combustion chamber temperatures.
Many emissions systems rely on an EGR valve to lower combustion chamber temperatures. Adding a small amount of inert exhaust gas when tlie engine is under load lowers the temperature in tlie combustion chambers just enough to reduce the formation of NO^sub x^. I've always thought this mediod was similar to feeding manure to a horse. Automotive engineers must agree because many vehicles now manage to control NOx without the help of an EGR valve. The Jeep you're working on is one such vehicle.
But everything else must be working properly if the EGR valve crutch is removed. As you correctly surmised, combustion chamber deposits can artificially raise the compression ratio and encourage the formation of NO^sub x^. Overaclvanced ignition timing can also cause NO^sub x^ formation. Since the Jeep does not have an externally adjustable ignition system, we should be able to rule it out as a possible cause in this case. Jury-rigging the ignition in an attempt to retard the timing is not an acceptable solution.
Check with the owner to make sure the PCM hasn't been "chipped" or modified in some other way. One quick and dirty way to increase engine performance is to change the spark advance curve. This used to be accomplished by changing the advance springs in the distributor. Now it's done by changing the PCM's timing decisions. Too much advance at the wrong time, caused by an aftermarket chip modification, could be responsible for the excessive NOx problem.
A lean air/fuel mixture can also encourage NO^sub x^ formation. The lean mixture can be caused by insufficient fuel pressure or volume, or the engine management system may actually be commanding the mixture lean. This could occur if the PCM is receiving bogus information from an oxygen sensor that has a lazy response rate or has become biased rich. Your emissions readings didn't include an Oo reading, which would have been helpful in determining whether the engine is running rich or lean under load.
Be sure to consult Sam Bells article on lambda in this issue ("What Goes In..."). The lambda calculation is a great way to determine whether an engine is running rich or lean, without having to concern yourself with other influences.
Last of all, an engine that's running hotter than normal will encourage NO^sub x^ formation. A faulty thermostat or a clogged cooling system could be keeping the Jeep's operating temperature just shy of overheating. Adding a load pushes the combustion chamber temperature to the point where NO^sub x^ formation increases to an unhealthy level. The engine should be producing almost no NO^sub x^ at idle. If the NO^sub x^ reading is high at idle, run through the NO^sub x^-influencing factors I've listed until you find the cause.
Copyright Hearst Business Publishing Sep 2005
Provided by ProQuest Information and Learning Company. All rights Reserved
Second, a lack of backpressure caused by the aftermarket exhaust system should not cause an increase in NO^sub x^, at least not on a vehicle that's capable of adjusting its own air/fuel ratio. Let's consider the things that can cause NO^sub x^ to increase to an abnormally high level. Oxides of nitrogen (NO^sub x^) are formed when the combustion chamber temperature exceeds 2500°F (the ignition point for compressed nitrogen). The engine must normally be under some kind of load before it develops such high combustion chamber temperatures.
Many emissions systems rely on an EGR valve to lower combustion chamber temperatures. Adding a small amount of inert exhaust gas when tlie engine is under load lowers the temperature in tlie combustion chambers just enough to reduce the formation of NO^sub x^. I've always thought this mediod was similar to feeding manure to a horse. Automotive engineers must agree because many vehicles now manage to control NOx without the help of an EGR valve. The Jeep you're working on is one such vehicle.
But everything else must be working properly if the EGR valve crutch is removed. As you correctly surmised, combustion chamber deposits can artificially raise the compression ratio and encourage the formation of NO^sub x^. Overaclvanced ignition timing can also cause NO^sub x^ formation. Since the Jeep does not have an externally adjustable ignition system, we should be able to rule it out as a possible cause in this case. Jury-rigging the ignition in an attempt to retard the timing is not an acceptable solution.
Check with the owner to make sure the PCM hasn't been "chipped" or modified in some other way. One quick and dirty way to increase engine performance is to change the spark advance curve. This used to be accomplished by changing the advance springs in the distributor. Now it's done by changing the PCM's timing decisions. Too much advance at the wrong time, caused by an aftermarket chip modification, could be responsible for the excessive NOx problem.
A lean air/fuel mixture can also encourage NO^sub x^ formation. The lean mixture can be caused by insufficient fuel pressure or volume, or the engine management system may actually be commanding the mixture lean. This could occur if the PCM is receiving bogus information from an oxygen sensor that has a lazy response rate or has become biased rich. Your emissions readings didn't include an Oo reading, which would have been helpful in determining whether the engine is running rich or lean under load.
Be sure to consult Sam Bells article on lambda in this issue ("What Goes In..."). The lambda calculation is a great way to determine whether an engine is running rich or lean, without having to concern yourself with other influences.
Last of all, an engine that's running hotter than normal will encourage NO^sub x^ formation. A faulty thermostat or a clogged cooling system could be keeping the Jeep's operating temperature just shy of overheating. Adding a load pushes the combustion chamber temperature to the point where NO^sub x^ formation increases to an unhealthy level. The engine should be producing almost no NO^sub x^ at idle. If the NO^sub x^ reading is high at idle, run through the NO^sub x^-influencing factors I've listed until you find the cause.
Copyright Hearst Business Publishing Sep 2005
Provided by ProQuest Information and Learning Company. All rights Reserved
Last edited by mt_goat; 11-19-2007 at 03:30 PM.
11-19-2007, 03:42 PM
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11-19-2007, 04:12 PM
#29
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it happens! lol anyway i was thinkin of testing it cooler but wasnt sure man im gonna be a emissions wiz after this lol anyway this has got me really puzzled is this common for this engine or just yotas?
11-19-2007, 04:20 PM
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Was'nt changing subjects at all another member asked why I switched oil grades was all... sorry for the topic drift...lol
as for the O2 throwing a code it might not. As long as it is still "working" you would'nt get a code though the device might be screwed up anyways...
as for the O2 throwing a code it might not. As long as it is still "working" you would'nt get a code though the device might be screwed up anyways...
11-19-2007, 04:30 PM
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lol thanks ok so why would an o2 sensor change the readings when everything else has been changed i mean the cats new and muffler is new but those are AFTER the o2 plugs should shift the readings better even at the o2 cause theres less gas in the exhaust is my thinking right or am i off?
11-19-2007, 05:06 PM
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Like someone said above, you are fighting a "lean/hot" problem. NOx is formed when combustion temps are too high, a lean mixure is one of those possibilites.
So things to look at that may cause hot combustion temps (maybe you have checked some of them already, but there are too many posts and threads to check now):
Check the TPS as per the manual
Check the VAFM as per manual
Check/change the O2 sensor
Check the coolant temp sensor for the ECU
Check the ignition timing
All of these devices influence engine fueling/spark, if any of them are out of whack, you could be running lean and having too hot of combustion, causing high NOx. They don't test for NOx in my state, so I have no experience with my truck and this, my only experience is from previous race car tuning and reading.
So things to look at that may cause hot combustion temps (maybe you have checked some of them already, but there are too many posts and threads to check now):
Check the TPS as per the manual
Check the VAFM as per manual
Check/change the O2 sensor
Check the coolant temp sensor for the ECU
Check the ignition timing
All of these devices influence engine fueling/spark, if any of them are out of whack, you could be running lean and having too hot of combustion, causing high NOx. They don't test for NOx in my state, so I have no experience with my truck and this, my only experience is from previous race car tuning and reading.
11-19-2007, 10:41 PM
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Very likely your EGR isn't opening while driving. The valve itself is probably ok, but the transducer that controls vacuum to the valve fails often. To test if your EGR opens while driving, tee in a vacuum guage at the EGR valve. Use a long hose so you can monitor the guage while driving. The guage should flucuate with the throttle up to about 5" hg. Cruise at 20-30mph, guage should read steady.
If you get no vacuum reading, then check the hoses and source ports for leaks/blockage. If they're ok you need a transducer (dealer only usually)
If you get no vacuum reading, then check the hoses and source ports for leaks/blockage. If they're ok you need a transducer (dealer only usually)
11-20-2007, 04:41 AM
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No more testing here in SW ohio either. It was a crappy system they had. Brand new cars were failing and smoke belchers were passing no problems. The testing facilities were privately owned so there were some questionable practices. I have personally had vehicles fail the first time because they werent completely hot yet. drive it around for another 20 minutes and come back and it passed fine.
11-20-2007, 05:31 AM
#35
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Another thing that can cause a lean condition is an air leak in the intake tubing after the VAFM (sits on top of the stock 3.0 air box). Check that tubing for cracks or loose clamps or PCV hoses dissconnected, loose or cracked. Any air that can enter after the VAFM is unmetered (and unfiltered BTW) so the ECU doesn't know that extra air is going in and that throws the A/F ratio off to the lean side. Great MPG but dangeriously hot combustion temps, that also makes more NOx.
11-20-2007, 05:48 AM
#36
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Well I thought I had put up a post on this but maybe I forgot to hit send.
You NOX readings are very high and I would at this point stop assuming that which is new is also good. A bad EGR while raising temps, should not raise it that high.
The first culprit I would look at is the new cat, it has the largest impact on NOX. The cat should be 50-100 degrees F hotter on the outlet than on the inlet. This can be checked with an infrared thermometer which one can get at Radioshack for 50 bucks or borrow one if you can find it.
If you are not throwing a code 71 than the EGR should be working.
How do your HC's look?
One scenario could be, if I read he order of part replacing correctly, is that a bad O2 sensor let the engine run too rich which makes the cat get very hot and can in many cases cause the internals to melt. Since you changed it you fixed that but possibly damage was already done. Just a thought.
Frank
You NOX readings are very high and I would at this point stop assuming that which is new is also good. A bad EGR while raising temps, should not raise it that high.
The first culprit I would look at is the new cat, it has the largest impact on NOX. The cat should be 50-100 degrees F hotter on the outlet than on the inlet. This can be checked with an infrared thermometer which one can get at Radioshack for 50 bucks or borrow one if you can find it.
If you are not throwing a code 71 than the EGR should be working.
How do your HC's look?
One scenario could be, if I read he order of part replacing correctly, is that a bad O2 sensor let the engine run too rich which makes the cat get very hot and can in many cases cause the internals to melt. Since you changed it you fixed that but possibly damage was already done. Just a thought.
Frank
11-20-2007, 06:08 AM
#37
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You did, he has 2 threads going for the same thing, but at least the other one has a better title. 
https://www.yotatech.com/forums/f116...higher-130228/
He says he's got good MPG, I don't see anyway he could be running rich and still get good fuel economy.
Also his new cat is $$$OEM$$$ which should be a great cat.
https://www.yotatech.com/forums/f116...higher-130228/He says he's got good MPG, I don't see anyway he could be running rich and still get good fuel economy.
Also his new cat is $$$OEM$$$ which should be a great cat.
Last edited by mt_goat; 11-20-2007 at 06:17 AM.
11-21-2007, 11:48 AM
#38
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just thought id take a min to say thanks to everyone for there input with my emissions problem! today was the last straw!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! had a mechanic take a look at things i KNOW him and trust him timing is A OK all the other options have been tried cat o2 muffler egr timing all pefect! so after having him look at things and all the parts i put in i have finally made it to the "you pass just for spending money point" the limit in ohio is 300.00 and with the receipts i have now i will be given a waiver for my 4runner which says I PASS and wont be hassled by the testing anymore woooohooo now its time for tires gears lift lockers and flares not sure what order they wil be in but wooooooooooohoooooooooo
09-26-2009, 06:37 PM
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I know this is an old thread but i wanted to let everyone know about a trick that i use to get by the california emmisions or smog test . Any truck will pass bad cat bad whatever , you run your car down to a gallon of fuel then add a gallon of denatured alcahol to your tank , go to smog shop and watch the smog guy scratch his head as your truck passes with flying colors , after test asap fill up with reg gas . This works everytime /
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