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mike foti
Dodge Dakota
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9/04/2005
17:37:39
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 Subject: failing emissions for nox
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Message:
I have a 93 dakota 5.2 with 120k miles that is failing for nox at 5.75 gmi limit is 3.75 gmi on the oregon emissions test (dyno test to 30 mph 4 times). I have already replaced the plenum gasket which was not blown but was leaking I also did 2 treatments of sea foam down the intake, egr valve is 2 years old and is working fine, ran 2 bottles of STP injection cleaner through the gas tank, egr passages and tube were cleaned thoroughly, 180 tstat was already installed, I put in the 1 step colder autolite plugs, new pcv valve, catcon was replaced (before the catcon and plenum gasket I was at 4.4 gmi on HC and 6.8 gmi nox now after the changes I am at .6 gmi for HC and 5.75 gmi nox). oxygen sensor has only 6k miles on it. I have had it into the shop twice so far, once before the repair work and once after and they say everything looks good as far as sensor readings. I have also had the diff fluid changed over to synthetic, and the transmission fluid and filter have also been changed just to try and lower the effort the engine has to put into turning the wheels a little. I only hear pinging on hard accelleration when I drive but when they do the test the engine pings half the time they are doing the test, the rollers seem to put more load on the engine than when it's driven. I have been through DEQ 3 times now and I'm running out of ideas. The only other easy thing I can think of is to fill up with premium and put in some fuel dryer to try and reduce the pinging during the test, this may raise the HC a little but I'm hoping it will drop the nox levels. The only other repair items I can think of are timing chain and distributer drive gear and bushing to rule out timing variability. Any advice would be greatly appreciated. Mike...
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b1llyw
GenIII
9/04/2005
17:41:00
| RE: failing emissions for nox
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Message:
You want to run hotter, not colder. Take the 180 t-stat out and put a 195 back in for the test. Run the stock heat range plugs, not the one step colder plugs. Not your best performance setup but will help you pass smog.
Is that your original fuel pump? Have you changed your fuel filter?
Bill White - KRC Performance
'03 SRT-4 w/goodies
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johnson
Dodge Dakota
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9/04/2005
18:40:05
| RE: failing emissions for nox
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Was the converter replaced with an OEM part is is it the "universal" type?
You might have a more serious underlying problem like worn rings or valve guides.
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mike foti
Dodge Dakota
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9/04/2005
19:33:57
| RE: failing emissions for nox
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I thought in order to help get rid of the pinging you want to lower the heat range of the plug and t-stat as has been stated on this board a number of times. The cat was replaced with a universal because the dealer wanted way more than I could afford at the time and from what I have read on this board the OEM cats seem to fail/ self detruct. passed before with a universal catcon. I have done a compression check and all cylinders are between 150-160 psi. I used to get some blue smoke on startup and after running in hot weather in a lot of stop and go tracffic but it would clear up once i got out of traffic, haven't had either of these problems since replacing the plenum gasket.
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mike foti
Dodge Dakota
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9/04/2005
19:35:40
| RE: failing emissions for nox
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The fuel pump was replaced at 60k and the filter on the frame was replaced 6k miles ago. mike
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mike foti
Dodge Dakota
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9/04/2005
21:21:38
| RE: failing emissions for nox
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One other thing I forgot to mention is that when I talked to the dealer about a new OEM catcon and I gave him the vin # he said that the truck is a high altitude model, which makes since since I bought it in albuqurque nm. I don't know what makes it high altitude or if the computer is set to run leaner and if that may be adding to my problems.
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b1llyw
GenIII
9/05/2005
06:44:30
| RE: failing emissions for nox
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Message:
Pinging is running lean and that's usually a good thing on an emissions test. Are you running 93 octane during your tests?
Bill White - KRC Performance
'03 SRT-4 w/goodies
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mike foti
Dodge Dakota
JOIN HERE
9/05/2005
10:59:55
| RE: failing emissions for nox
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Message:
The problem with running lean and having pinging (detonation) is that I believe it causes spikes in combustion temperature and pressure which leads to the formation of NOX. I was running 87 octane during the last test. I am going to try premium tomorrow and see how it does. It may increase my HC but I'm only at .6 and the limit is 2.4 so I should be ok there. My CO is at 1.9 gmi and the CO2 is at 830 gmi, so the engine seems to be burning everything ok. It's just NOX at this point. Any other suggestions? Mike
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Kowalski
GenIII
9/05/2005
17:41:35
| RE: failing emissions for nox
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Message:
Did you use Bill's other suggestions about the T'stat and plugs ? He's right about lower emissions at higher temps.
Lead, follow, or get out of the way
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mike foti
Dodge Dakota
JOIN HERE
9/05/2005
18:02:17
| RE: failing emissions for nox
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Message:
The interesting thing about the temp is with the 180 tstat installed I usually run between 1/4 and 3/8 on the temp gauge and on the emissions test report the middle 2 cycles are the best for nox and on the last cycle nox creeps back up. when I get back in the truck after the test the gauge is between 1/2-3/4 and the truck pings noticeably until the temp comes back down after driving it a bit. I did run the truck through with the proper heat range plugs and now I'm just trying every little thing to drop the nox levels a little more. The first test before i did anything was at 7.9 gmi and now I'm down to 5.75 gmi. I agree about higher temp being better for HC and CO but don't you want lower temps for reduction of nox levels? mike
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mike foti
Dodge Dakota
JOIN HERE
9/07/2005
13:22:48
| RE: failing emissions for nox
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Message:
just back from DEQ, the truck finally passed, I filled up with premium and after that I couldn't get it to ping even on hard accelleration and no pinging during the test. NOX dropped from 5.75 to 2.28 (limit 3.75) which is the best I have gotten out of the 4 times I have registered the truck. HC came up from .6 to .99 (limit 2.4) and CO went up from 1.9 to 5.9 (limit 80) CO2 was still close to 800.
Mike
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b1llyw
GenIII
9/07/2005
13:26:05
| RE: failing emissions for nox
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Message:
Congratulations! You passed, that's all that matters. How often do you have to test where you live?
Bill White - KRC Performance
'03 SRT-4 w/goodies
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mike foti
Dodge Dakota
JOIN HERE
9/07/2005
18:47:38
| RE: failing emissions for nox
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Message:
we have test and register every 2 years so I have some time to figure out why the truck still tends to run lean, but for now i'll just keep running 89 or 92 octane.
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