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Thread: 5.7L running too lean (very high NOx), won't pass state emissions

  1. #1
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    5.7L running too lean (very high NOx), won't pass state emissions

    I have an 89 Jeep Wrangler with a 95 Chevy 5.7L TBI crate motor mated to a 700R4 trans. The computer (1227747), wiring harness and all sensors are out of a 92 chevy truck. Since the 700R4 is non-electronic, it has the 1227747 computer. This setup was installed in 2000 but it only has about 8,000 miles on it since the vehicle was primarily used for off-road. The main problem is NOx are very high around 1300 (max allowed is about 800). California does emissions testing at 15mph and 25mph which is about 1600rpm on this vehicle - so part throttle. High NOx means the combustion chamber is running way too hot because the engine is running too lean. I had a certified mechanic check it out a few months ago. He thoroughly checked the EGR components, no vacuum leaks, TPS and other sensors, timing, replaced O2 sensor, replaced coolant temp sensor (the one that feeds the ECM), new catalytic convertor, switched fuel canister & purge system from Jeep to Chevy, etc. Engine starts right up, idles fine, and has plenty of power. Also, replaced P/N switch and wired it with a new starter relay so ECM B10 get a ground if shifter in P or N. So, I purchased the Moates Extreme ALDL hardware and cables and TunerPro RT (using $42-1227747-V5.2.adx). Data is streaming fine and I have attached my XDL file which shows cold engine through normal operating temperature (about 200 degrees). I am new to reading the TunerPro RT results, but it looks to me like the ECM goes into closed-loop mode when the coolant reaches about 115 degrees, BLM holds pretty steady around 128 but occasionally goes into low 130's. I did notice that once fully warmed up and at part throttle, the O2 sensor output seems to be quite low (100mv or less) and the Rich/Lean parameter pretty much stays Lean - event hough the BLM remains steady at 128. I don't quite understand this. So, can someone take a close look at my attached XDL file and perhaps explain what is going on? I haven't measured the fuel pressure since it is a pain to get to the metal line under the rear of the throttle body with the engine crammed in a Wrangler.

    Lee
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    Last edited by bigmac; 03-10-2017 at 06:47 PM.

  2. #2
    Fuel Injected! uncabob's Avatar
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    Hi bigmac:
    Just curious about your O2 sensor: Is it a heated sensor? Is it located in or near the manifold or collector? Do you have headers or cast iron manifold?
    What size exhaust pipes and are they dual going into a Y or crossover? One cat or two?
    Bob

    ps Didn't look at your .xdl.
    Last edited by uncabob; 03-09-2017 at 07:54 AM.
    Don't force it, get a bigger hammer!

  3. #3
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    O2 is single wire (non-heated). It is located in the rear of the passenger side ceramic header (just above the collector area). Driver side exhaust connector pipe runs under oil pan to a y-collector on passenger side. A single 3" diameter exhaust pipe runs from the y-connector to a new cat then to a muffler then over the rear Dana60 axle terminating under the bumper.

    Lee

  4. #4
    Fuel Injected! uncabob's Avatar
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    May not be getting hot enough? If nothing else is obvious you may want to go to a heated sensor.

    Bob
    Don't force it, get a bigger hammer!

  5. #5
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    Thanks Bob. I will look into converting to a heated O2 sensor.
    Lee

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    If the 02 sensor was cooling off the engine would run rich, not lean. I would check your base timing and make sure it is set for TDC or 0*BTDC. Also check the base fuel pressure the engine is running at. These engines like to be in the 12-13 psi range even with a stock engine. Maybe as much as 14 psi with a higher flowing intake/exhaust setup. Finally check your injectors to make sure that you have the 61 lb/hr injectors, not the 46s or 55s from a 4.3 or 350. I would also suggest that dropping the coolant temp will help prevent the formation of NOx emissions. A 180*F thermostat will drop the numbers some as well.
    Last edited by Fast355; 03-09-2017 at 10:48 AM.

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    Fast355, I will check the timing and fuel pressure. However, I have a question about the injectors. Since this is a throttle body with two injectors, how do I tell what size they are? If I remove them, will there be a number somewhere on them? I have attached two photos, one shows Rochester Products 155Z64 and the other a number 312. As you can see from the pictures, both are on the throttle body. I don't know if the injectors have separate part numbers.
    Lee
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  8. #8
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    Quote Originally Posted by bigmac View Post
    Fast355, I will check the timing and fuel pressure. However, I have a question about the injectors. Since this is a throttle body with two injectors, how do I tell what size they are? If I remove them, will there be a number somewhere on them? I have attached two photos, one shows Rochester Products 155Z64 and the other a number 312. As you can see from the pictures, both are on the throttle body. I don't know if the injectors have separate part numbers.
    Lee
    If they are GM injectors the factory part number will be eteched into the top of them. Should be able to read the numbers without removing them.

    I know my old TBI in my 1983 G20 van passed with a fraction of the allowable limits. It was also not stock at the time. Had an edelbrock intake, 454 TBI unit, open center TBI spacer, 1.6:1 roller rockers, and doug thorley tri-Y headers feeding a large high flow 3" converter.

    This was the last smog test it ever had to go through.


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    This part number is on the injector body AC 112. Next to it is another number 17064317. However, when I search AC Delco's website, it says both numbers don't exist. See
    Lee
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  10. #10
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    Quote Originally Posted by bigmac View Post
    This part number is on the injector body AC 112. Next to it is another number 17064317. However, when I search AC Delco's website, it says both numbers don't exist. See
    Lee
    If they are factory injectors where the injector connector clips there will be two painted strips. A 350 truck injector will be Orange/Black.

  11. #11
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    Quote Originally Posted by bigmac View Post
    This part number is on the injector body AC 112. Next to it is another number 17064317. However, when I search AC Delco's website, it says both numbers don't exist. See
    Lee
    If they are factory injectors where the injector connector clips there will be two painted strips. A 350 truck injector will be Orange/Black.

    The pic you posted is for the fuel meter body. Each injector will be stamped itself. Under the injector connector.

  12. #12
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    These are Marine high pressure injectors. Pink/Purple....Notice the rusty looking area on them. That is the factory stamping ID.


  13. #13
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    Well, here are three photos of my injectors. One of them shows the orange and green wires and an orange marking on the front side of the first injector. The second photo clearly shows a black marker on the back side of the first injector. The third photo is looking down into the bottom of the first injector where if you zoom the picture you can see a large number 5 on one side and I think a small number 02360. So, are these 60lb injectors?
    Lee
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  14. #14
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    Quote Originally Posted by bigmac View Post
    Well, here are three photos of my injectors. One of them shows the orange and green wires and an orange marking on the front side of the first injector. The second photo clearly shows a black marker on the back side of the first injector. The third photo is looking down into the bottom of the first injector where if you zoom the picture you can see a large number 5 on one side and I think a small number 02360. So, are these 60lb injectors?
    Lee
    Those are 61s.

  15. #15
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    So, injectors are good. I also tested the fuel pressure at the outlet of the fuel filter and it measured 14lbs. See attached photo. Since the fuel pump is in the tank and it is a pain to get to the metal fuel line connecting at the bottom of the TBI, I took the easy way and measured it at the fuel filter.
    Lee
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