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Discussion Starter · #1 ·
Ok, no sooner do i finally get my 2001 Passport back from the suspension rust recall..problems. On the way home the truck seemed to stumble around 2.5k-3k in RPM. A slight rumbling could be felt in the truck. It doesn't seem like a transmission slip because the truck continued to accelerate. If I step on the gas more causing it to downshift, it goes away. Right now I am at a loss.

I did a fluid and filter change on the transmission 4-5k in miles ago. The truck sat in the hands of previous owner. I've done a TON to this truck in the way of maintenance.

Everything from the t-belt/water pump, fuel filter, plugs, etc.

Anyone know the best way to diagnose a slip?

I am thinking it could be my plugs. I've gotten a random misfire code before that tripped a CEL. Haven't gotten it since. I have the Denso plugs that are factory for the truck but have yet to put them in.

What's the best way to rule out the transmission?
 

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At that rpm the butterfly's are opening in the intake plenum. They can get sticky/gooey and make for a stumble/flat spot...Start with checking your tranny fluid, make sure it's topped off... If you reach to the back of your intake you can feel and move the butterfly linkage,See if it feels stiff.
 

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Discussion Starter · #3 ·
Its a fly by wire. The butterfly is controlled by an actuator.

Truck ran fine today with no slip in the transmission at all. I have a feeling this has something to do with an wet electrical connection somewhere. Whatever happened...it was below the threshold of tripping a code. Plugged the scanner into it. Nothing in freeze frame, pending, or trouble. It happened to my father once before and it threw a P0300 code.

Wondering if this is the ION sensing system not liking my plugs + the wet weather.
 

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Mine does that to I need to get the super special plugs for it. But I know that it's plug related so I'm putting it off lol... Mine is fly by wire to... It's a combination of the intake runner butterfly's and the plugs I think. A few people have had issues with the wiring harness having stretched/pinched, or pulled/broken wires, where it runs to the engine. Drivers side main harness loom. Not loose enough to flex with the engine. I plan on unwrapping it and redoing it so the wiring can move freely.
 
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