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Discussion Starter #1
Long story short bought a 3.7l nitro and had a broken valve seat, replace cylinder, timing chain kit and all new gasket, water pump, injectors, coil packs and MAP sensor.

Currently getting only p0172, stumble a bit on idle. I do smell gas and once warmed up long enough it back fire a bit only on idle, While driving no problem at all and has a ton of power.

i have the data from my scanner, if any one can point me in the right direction, it will greatly be appreciated.

38609
38610

38611

38612

38613
38614
 

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Short and Long term fuel trim 2 (%) and ST FTRM21 (%) both are high negative. Suspect the 2 refers to bank 2 on the engine (right side). Looks like upstream O2 sensor. When it comes to sensors, especially oxygen sensors, I recommend OEM only.
 

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Discussion Starter #4
Short and Long term fuel trim 2 (%) and ST FTRM21 (%) both are high negative. Suspect the 2 refers to bank 2 on the engine (right side). Looks like upstream O2 sensor. When it comes to sensors, especially oxygen sensors, I recommend OEM only.
Would a faulty o2 sensor cause the car to run rich? I smell the fuel on start up from the exhaust.
 

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Discussion Starter #6
here is a video from Diagnose Dan (i learnt loads from his videos), that might help explain O2 sensors a bit more in depth,
I’m going to replace both up stream o2 sensor sometime this week and see if that works.
 

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wiring diagram says oxygen sensors 1/1 and 1/2 are left side of transmission, sensors 2/1 and 2/2 are right side of tranny, just not sure which 2 are up Stream or down stream
 

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Discussion Starter #9 (Edited)
wiring diagram says oxygen sensors 1/1 and 1/2 are left side of transmission, sensors 2/1 and 2/2 are right side of tranny, just not sure which 2 are up Stream or down stream
Up stream o2 sensor is before catalytic converter and down stream is in the catalytic converter, so 1/1 is bank 1 sensor 1 which is up stream and 1/2 is bank 1 sensor 2 down stream vise versa with 2/1 and 2/2

Now honestly from the video it confirm I’m running rich with the negative fuel trim, it my first time using the data and seeing all the value, going to see if I can find factory specs and compare and need to do some more learning
 

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If you replace one O2 sensor and not the other, on one side, you can also run into issues. Because of this, it is recommended to replace both up and downstream on one side.
 

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Up stream o2 sensor is before catalytic converter and down stream is in the catalytic converter, so 1/1 is bank 1 sensor 1 which is up stream and 1/2 is bank 1 sensor 2 down stream vise versa with 2/1 and 2/2

Now honestly from the video it confirm I’m running rich with the negative fuel trim, it my first time using the data and seeing all the value, going to see if I can find factory specs and compare and need to do some more learning
Factory specs are the industry standard called the stoichiometric ratio, which is your air to fuel ratio (14.7:1). Any mixture greater than 14.7:1 is considered a lean mixture; any less than 14.7:1 is a rich mixture. High negative fuel trim percentage indicates a rich mixture. Fuel trim should be near zero. Zero is 14.7:1. One gram of fuel to 14.7 grams of air.

Your upsteam O2 sensor is likely contaminated or damaged from the cylinder head failure.
 

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Would a faulty o2 sensor cause the car to run rich? I smell the fuel on start up from the exhaust.
As soon as the O2 sensors enters closed loop a faulty sensor will skew fuel trim. In open loop fuel trim is set based on many factors, but mostly coolant and intake air temps. O2 sensor heaters quickly get fuel delivery running in closed loop. Upstream and downstream O2 sensors are nearly everything when it comes to fuel trim delivery. They have the greatest input on injector on-time.
 

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Discussion Starter #13
Ok I would like to update, I replace both upstream o2 sensor and the rich code went away and now only have a misfire in cylinder 2.

when I replaced the passenger side cylinder head and and rebuilt the engine I have 120psi in all 6 cylinder but being that I didn’t know there was a fill port on the water pump housing, the engine didn’t have enough coolant to circulate the coolant and over heated and dropped cylinder 2 exhaust valve seat. Gonna replace that cylinder head and all should be fine
 

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Discussion Starter #14 (Edited)
ok well seem like my compression tester failed on me. Put cylinder 2 at tdc and no valve leak or bottom end leak, going to replace spark plug and check spark on cylinder 2 and see if it run fine
 

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Discussion Starter #16 (Edited)
@NitroTech @Scar0
I’ve been playing with the car and monitor the 02 fuel trim and etc. So on cold start I visibly see white smoke from the exhaust and smell gas until the engine is warmed up about 3min or so and smoke is gone and the excessive gas smell is gone.

bank 2 upstream fuel trim is -10 or so does Jump around a lot on idle, while holding 1.5k -2k rpm the fuel trim is positive like its running lean. I can get the fuel trim to behave identically to bank 1 by removing any of the injector on bank 2 and putting it back in, even with the random misfire it will match the fuel trim on bank 1 on idle and revving the engine. I’m stumped and only thing I can think about is the egr valve being that it’s on bank 2 exhaust manifold
 

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@NitroTech @Scar0
I’ve been playing with the car and monitor the 02 fuel trim and etc. So on cold start I visibly see white smoke from the exhaust and smell gas until the engine is warmed up about 3min or so and smoke is gone and the excessive gas smell is gone.

bank 2 upstream fuel trim is -10 or so does Jump around a lot on idle, while holding 1.5k -2k rpm the fuel trim is positive like its running lean. I can get the fuel trim to behave identically to bank 1 by removing any of the injector on bank 2 and putting it back in, even with the random misfire it will match the fuel trim on bank 1 on idle and revving the engine. I’m stumped and only thing I can think about is the egr valve being that it’s on bank 2 exhaust manifold
Disconnect both battery terminals and hold clip them together in some way, leaving them for 5 minutes. This will discharge and clear your PCM memory. Reconnect the terminals to the battery and go for a road test. Once the vehicle is at operating temperature and driving down the highway at about 60mph perform a closed throttle decel. Foot completely off the accelerator pedal. This will relearn your cam/crank numerator and your fuel adaptives will relearn from scratch.

You may also need to replace the downstream. Downstream O2 drives upstream. But perform the procedure above first and let us know.
 

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Discussion Starter #18
Disconnect both battery terminals and hold clip them together in some way, leaving them for 5 minutes. This will discharge and clear your PCM memory. Reconnect the terminals to the battery and go for a road test. Once the vehicle is at operating temperature and driving down the highway at about 60mph perform a closed throttle decel. Foot completely off the accelerator pedal. This will relearn your cam/crank numerator and your fuel adaptives will relearn from scratch.

You may also need to replace the downstream. Downstream O2 drives upstream. But perform the procedure above first and let us know.
Ok I may have to do that tomorrow morning because there a curfew in Pennsylvania, but I’m going to check cylinder 4 and 6 at tdc and make sure there no valve leaks to eliminate that as the cause of the erratic 02 reading I’m getting. I also have a new camshaft sensor That I can install and I have a crank shaft sensor on the way as well, I also haven’t let the computer go through it’s cycle to see if maybe the catalytic convertor is bad
 

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Discussion Starter #20 (Edited)
@NitroTechI also would like to mention I did get a couple other code before I erased them but I brushed off as nothing, but one was something about mis matching vin, another was implausible data the last one was erratic something, hoping they come up again
 
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