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98 durango negative fuel trim

  • Dynamo786
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09 Mar 2019 15:01 #27693 by Dynamo786
98 durango negative fuel trim was created by Dynamo786
Have a 98 durango with a 318

Its been surging real badly when i drive it. Seems like the only way i can drive it is if i floor it.

Took it to have the codes scanned and there were none.
The fuel trim was maxed out rich (-33% ltft)
O2 s1b2 was hovering around 1v constant exept when i gave it some gas then it dropped raised to 1.2ish
The other side was normal.

I was thinking a injector was stuck open, but i dont know how to test them and see which one is bad w/o blasting it with the parts shotgun.
Someone else recomended a regulator.

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  • cheryl hartkorn
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09 Mar 2019 15:10 #27694 by cheryl hartkorn
Replied by cheryl hartkorn on topic 98 durango negative fuel trim
your problem is in the bank 2 sensor 1. if its -33 that sensor should be reading dead lean 100 mv or less. try unplugging the sensor and see what it reads then. what does bank 1 sensor 1 read

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  • Dynamo786
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09 Mar 2019 15:14 #27695 by Dynamo786
Replied by Dynamo786 on topic 98 durango negative fuel trim
Really? The opposite sensor reads normal.

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09 Mar 2019 17:00 - 09 Mar 2019 17:06 #27698 by guafa
Replied by guafa on topic 98 durango negative fuel trim
Ok please let me get straight ahead with this.

O2s1b2 LTFT is minus 33% and voltage in upstream bank2 is between 1 - 1.2v?

That means PCM is subtracting fuel because O2 sensor line readings are rich.

You can unplug one or two injectors (with engine running) and see what happend with O2 sensor voltage. If voltage goes down, O2 sensor could be good and you have an injector issue. Also you can have a fuel likeage from fuel regulator.
Last edit: 09 Mar 2019 17:06 by guafa.

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  • Tyler
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10 Mar 2019 11:19 #27717 by Tyler
Replied by Tyler on topic 98 durango negative fuel trim
Are both banks showing maxed rich? Or just bank two?

I agree with Cheryl, unplug the bank two upstream sensor and see if the symptom goes away. It sure sounds like it's either stuck rich or shorted to voltage.

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10 Mar 2019 14:17 #27725 by guafa
Replied by guafa on topic 98 durango negative fuel trim
Ok guys. I'd love dynamo786 let us know once issue is fixed.

Tyler, is it possible stuck rich? How could it happend? I understand reference PCM voltage is 0.45v.

Is it possible shorted to voltage when you have 1 to 1.2v oscillation?

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  • Tyler
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10 Mar 2019 18:50 #27730 by Tyler
Replied by Tyler on topic 98 durango negative fuel trim

guafa wrote: Tyler, is it possible stuck rich? How could it happend? I understand reference PCM voltage is 0.45v.


Totally possible! Uncommon, but possible. SD has a video covering this:



Is it possible shorted to voltage when you have 1 to 1.2v oscillation?


Also possible? Depends on if it's a hard short or a resistive short (across green crusties, water, like that). Mostly, I'd be intersted to know if the symptom disappears when the O2 is unplugged, AND what the O2 voltage reading is with the O2 unplugged.

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14 Mar 2019 00:40 #27800 by wacoeagle
Replied by wacoeagle on topic 98 durango negative fuel trim
in my experience surging usually is a bad fuel management sensor, its trying to correct itself, check the maf, coolant temp sensor Iac, , thermostat, EGR, PCV, check for leaking vacuum lines, leaking brake booster, throttle position sensor. many times these wont set a code for being bad themselves, but show up as other codes in a cause and effect situation.

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14 Mar 2019 00:42 #27801 by wacoeagle
Replied by wacoeagle on topic 98 durango negative fuel trim
also, is it surging as soon as you start it> or in closed loop once its warmed up. ?

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  • Dynamo786
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17 Mar 2019 12:22 #27893 by Dynamo786
Replied by Dynamo786 on topic 98 durango negative fuel trim
The vehicle isn't necessarily mine, I made this post for an aquantice of mine at work.

If i ever learn what happened with it or if he fixed it i will let you great folks
know!

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