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Continuing O2 failures


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1 minute ago, hakukamana said:

Coolant temp switch on the block, operating temperature readings are correct, from cold start up to full operating temperature. I can monitor the temperature as the truck heats up after the thermostat opens runs about 187 at idle.

What you are monitoring is what the ECU sees? You know that for a fact?

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2 minutes ago, hakukamana said:

I am monitoring the data off the scanner, MT2500. Short of using a Lazer temp gun, which I have, how else would I verify temperature?

What I'm wondering is if your temp sender is bad..........ECU sees cold temp, runs rich. (not the gauge sender......the other one)

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The failures of the O2s we're open loop, Lean, not rich,  and the voltages were way off, not swinging from low to high,  it was like the heater fried, and then the rest of the sensor just went wacko. I just would not think (3) bad O2 sensors. But each one that failed, initially worked fine for a couple of days. Then just stopped working correctly. The latest one was installed today, and it's working

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:popcorn:I am watching.

 

I have an 87 4.0 with a 90 manual trans ECU.  I also have Nickintime's REM to read the codes.

 

I am having an issue with LTFT stuck at 154.  That is running rich.  I recently replaced the O2 sensor with a Bosch (replaced a NTK/NKG).  The REM shows the O2 voltage jumping up and down from 1.xx to 4.xx, like it is supposed to do.  The REM shows I am in CLSD loop, like it is should be.  The STFT is constantly changing, BUT is continuously below 128, running lean.  It mostly is showing double digits - 10 to 90.  Sometimes it will drop to zero.  If it stays there for 3 seconds, the ECU switches to OPEN loop (like is should).

 

However, the LTFT NEVER changes!  What can I do to fix/adjust the LTFT?

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19 hours ago, Ωhm said:

I'm not saying that, I'm wondering if it will. LTFT should trigger when STFT reaches one of its two limits (0 or 255). LTFT will then move lower or higher, allowing STFT (128) to start all over again. Thats the intent of STFT and LTFT. Now what I don't know is if RENIX will do this.

I had a similar question to Ohm, LTFT is triggered by STFT hitting limits, then and only then would LTFT adjust itself depending on the triggered limit STFT hit? If you read the last sentence, thats the question, does the Renix ECU actually adjust the LTFT if the STFT hits a limit. I know as of this morning my LTFT is 128 rock solid no movement, the STFT is all over the place moving up and down in the 70's to the High 80's. But the scanner is showing voltage changes from lean to rich, it is running in closed loop, and the sensor appears to be operational at this point.

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There scanner definitely reads the CTS in the block. I tested my theory today and unplugged the one in the intake with the scanner hooked up. It still reads a coolant temperature and the gauge doesn't register.

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I too, would like to know more about this subject (STFT LTFT). I wonder if all ECU's are created equal. Does a 90 ECU offer more than say a 87 ECU, when it comes to Fuel Trim. 87MJTIM shows LTFT at 154 while other ECU's LTFT don't move and vehicle goes CLSD loop once STFT pegs one way or the other. Anyone else show LTFT movement? What year ECU?

 

87MFTIM does your LTFT value stay the same between KEY ON and KEY OFF cycles? If so, does that indicate Keep Alive Memory (KAM).

 

1 hour ago, 87MJTIM said:

I am having an issue with LTFT stuck at 154.  That is running rich.

Doesn't 154 mean engine is running lean and LTFT is increasing INJ PW time?

 

1 hour ago, 87MJTIM said:

The STFT is constantly changing, BUT is continuously below 128, running lean.

Just the opposite here, doesn't below 128 mean engine is running rich and STFT is decreasing INJ PW time?
 

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29 minutes ago, Ωhm said:

I too, would like to know more about this subject (STFT LTFT). I wonder if all ECU's are created equal. Does a 90 ECU offer more than say a 87 ECU, when it comes to Fuel Trim. 87MJTIM shows LTFT at 154 while other ECU's LTFT don't move and vehicle goes CLSD loop once STFT pegs one way or the other. Anyone else show LTFT movement? What year ECU?

 

87MFTIM does your LTFT value stay the same between KEY ON and KEY OFF cycles? If so, does that indicate Keep Alive Memory (KAM).

 

Doesn't 154 mean engine is running lean and LTFT is increasing INJ PW time?

 

Just the opposite here, doesn't below 128 mean engine is running rich and STFT is decreasing INJ PW time?
 

:blush:My bad. I got rich and lean backwards.  154 LTFT is increasing the pulse width.  My MPG has sucked!

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LTFT only changes over time thus long term. STFT fluctuates until you reach operating temp thus short term. I can't find a positive answer on what way is rich and what way is lean. Everywhere I look has opposite answers. My STFT starts at 128 which I believe is default. From there as it warms up it drops to the 90's which makes sense my LTFT is 91. So am I rich or lean on LTFT?

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It's confusing, yes. Number below 128 take fuel away (decreasing INJ PW time, O2S sees RICH engine). Number above 128 add fuel (increasing INJ PW time, O2S sees LEAN engine). In your case O2S sees RICH engine.

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Is there a Renix fuel injection guru on the forum? I started the post to try an understand the reasons for my failures of O2 sensors. I don't think Renix ECU's had KAM, then it would be able to store data, ie codes? But the understanding of the relationship between STFT and LTFT as controlled by the ECU is interesting, but I have looked through all my manuals including the Renix FI, manual and nothing specific

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3 minutes ago, hakukamana said:

Is there a Renix fuel injection guru on the forum? I started the post to try an understand the reasons for my failures of O2 sensors. I don't think Renix ECU's had KAM, then it would be able to store data, ie codes? But the understanding of the relationship between STFT and LTFT as controlled by the ECU is interesting, but I have looked through all my manuals including the Renix FI, manual and nothing specific

 

See the attached link for the Renix Fuel Injection Manual. A handy booklet to have.

 

http://alpinefurniturestore.com/JeepDocumentation/MJs/Jeep_Renix_Fuel_Injection_manual.pdf

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Screenshot_20190307-172623.png.c7919f4e709b386f8f6a50923c9a7895.png

If I'm reading this correctly 0 is ultimate rich and 255 is ultimate lean. This is a screen shot out of the Renix infection manual. So hopefully it right.

On 2/26/2019 at 3:32 PM, WahooSteeler said:

They had already replaced stock 1 holes with 4 hole units and were happy with them, but then recently went to the newer 12 hole units. They both seemed to feel the idle and throttle response improved again, much like it had when going from 1 to 4 hole. Others reported additional MPG gains............

 

Limey, after more research, apparently stock flow rate is 23.2/lb which is interesting considering that I had planned on the 746's based on many discussions here. 746's come to find out are rated at 20.2/lb. Also have seen a lot of info on people running 703's (23/lb) on Renix 4.0's because they have the same EV1 connectors. 99+ guys seem to mostly run 784's (24.4/lb), they have the EV6 connectors. 

 

I just want to make sure when I purchase "new" units, I've got the best ones suited for my stock Renix 4.0L and only have to swap them once. 

And if I'm reading this right mine is rich beacuse the 746 injectors are 20.2/lb and stock injectors are 23.2/lb? So the ECM is compensating? Sorry too high Jack your post. Just want to understand this fuel trim thing.

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35 minutes ago, JMO413 said:

Screenshot_20190307-172623.png.c7919f4e709b386f8f6a50923c9a7895.png

If I'm reading this correctly 0 is ultimate rich and 255 is ultimate lean. This is a screen shot out of the Renix infection manual. So hopefully it right.

And if I'm reading this right mine is rich beacuse the 746 injectors are 20.2/lb and stock injectors are 23.2/lb? So the ECM is compensating? Sorry too high Jack your post. Just want to understand this fuel trim thing.

Meaningless without known fuel pressure. Pressure effects actual fuel delivery at the injector. 

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