I had my 2005 automatic v6 3.5 pathfinder’s piston rings changed and a bit later got the engine tweaked to reduce the emissions. Since about one of those events I have experienced some serious and random power detriments. Some days it works perfectly fine, some others it will make an enormous effort to reach 4K RPM and make a less smooth gear shift than when it’s running well (making a smooth “jump” or leap when shifting, as if you would release the clutch while over revving on a stick shift car). Making it impossible to reach over 35mph when it’s in this condition. When it’s fine it will glide through 60mph. I had the fuel pump changed but didn’t make any difference.
Any help is extremely valuable, I’ve been struggling with this for months now.
@Ccv
Sounds Like When It’s “In This Condition” The Engine Is Defaulting To Limp Mode, Which Would Explain The Rough Shifts And Trouble Going Over 35 MPH.
Do you get a “Check Engine” Light or message such as “Engine Power Reduced” ?
Have you had the vehicle checked for DTCs (Diagnostic Trouble Codes)?
What emissions tweaks were made? Not even sure what that means.
Piston rings is major engine work. Was there any other damage?
I suspecting there’s more to this story. CSA may be right…if the check engine light was on and the computer went into limp mode…but it doesn’t sound like that.
I’ve never heard of anyone here posting they got their cars piston rings replaced, and only the piston rings. Usually if the piston rings are replaced, there’s more than that done at the same time. If it was indeed just the piston rings, I expect you might have actually needed more work done, but decided to risk just doing the piston rings.
Since there are no diagnostic codes, no indication of “limp mode” being activated, the next step would a compression test. Suggest you have that done, and post the results here. It could be something else, but I think that’s the next step.
@GeorgeSanJose
"Since there are no diagnostic codes, no indication of “limp mode” being activated, the next step would a compression test. Suggest you have that done, and post the results here. It could be something else, but I think that’s the next step."
George, what am I missing? I didn’t see any indication that there are no DTCs, nor an indication that the vehicle doesn’t go into Limp Mode.
I was waiting for Ccv to comment on those items. CSA
The OP can count me as one more forum member who would like to hear the details about replacement of the piston rings in his Pathfinder’s engine. I think that some background on this matter is necessary before coming up with a valid theory regarding his current problem.
A lot of people , including me at times , jump from forum to forum looking for help when they have a problem with their vehicle . What they don’t realize is the amount of helpful knowledge that is available on this forum if they’d just come back & participate in the discussion .
I understand that as before I found this forum I have posted questions on several forums & either got I know it all & you’re an idiot type answers or lots of views to my questions & no really friendly , helpful & knowledgeable people willing to help .
I’m sorry for not having replied to your kind help intentions. I thought I’d receive email notifications when my post received replies. I haven’t been jumping around forums. The car has the exact same problem at the moment, and it still comes and goes randomly. Answering, the car does not throw any codes with the OBD. It is, in fact, just the piston rings that were replaced.
As for some background, this is my father’s car. He bought it with around 75k miles, in a pretty good shape and a low price due to blown airbags after a crash it had. We live in Ecuador. When he went for the city’s circulation test, it didn’t pass because of too high emissions, so the conclusion was that the engine needed to be repaired. As his budget was fairly low, he did a basic piston ring replacement.
Sometimes a simple piston ring replacement can work wonders, but that’s the exception rather than the rule with modern engine technology. Usually if an engine requires the piston rings be replaced, there are a bevy of other issues – minor and major – that need to be sorted out at the same time. But it is entirely possible the piston ring replacement was the only thing needed, and the current problem is some kind of intermittent sensor or computer problem unrelated to the ring job. But before going down the sensor/computer road, you were advised above to get a compression test. Has that been done? If so, post the results.
That makes sense @GeorgeSanJose, I have been thinking as well that an electric problem might be causing the issue. I will get a compression test and post the results. Am I wrong if I think I may get different compression values for when the car is working well and when it’s decayed?
HOLY MOLY…Replaced the PISTON RINGS??? Do you realize what you are saying with those 4 words?
Rings…are a SERIOUS “repair” Pathfinders piston rings usually outlast their owners and the vehicle before rings come into play…This is of course with basic maintenance and oil changes.
If your Piston Rings were actually replaced…Did they rebuild everything else while they stared at your engine completely dis assembled? Or don’t tell me they did the job from the Bottom Up and dropped the crankshaft out and proceeded.
I’m with many others here …and collectively we know MORE than A Lot about this stuff…
The piston ring replacement comment throws many of us into a bit of a tailspin…bec to do THAT job properly? Is called an Engine Rebuild…which suggests engine out and in pieces and every single physical connection to the vehicle to be temporarily UNDONE…until engine repairs dictate it goes back under the hood…then all the connections are Re Attached…
This leaves the possible causes of erratic behavior SO WIDE OPEN…that none of us will be able to really properly advise you on this. At this point in time…you need engine codes.
We would need a TON more info to direct you to a solution
Lets assume I IGNORE your piston ring comment… I would start leaning toward and engine misfire…oil leaking into plug wells…bad wires…Ignition stuff… Then move toward the MAF and other areas… This is IF we ignored the piston ring replacement comment.
But BOY HOWDY…when you tell us the “Rings” were replaced… REAL car guys here had a small “Kiniption”…I promise you that. Those 4 words basically throw all of our ideas into the “Possible” pile at that point. I also am suspicious as to how you were convinced to let them perform this “Repair” The bill should have been astronomical…and nowhere near a sensible type of thing to consider unless you were Born or Conceived in the vehicle and have unusually strong attachment bonds to the thing.