2003 Pathfinder Acceleration Problem, Power Valve?

[BigJim1]

I just completed putting new seals on my valve covers on our 2003 Pathfinder 3.5 LE. The engine ran perfect before this repair. I replaced all of the smaller vacuum hoses as they were crumbling. I did have two of the hoses crossed but have them straightened out now. There was one I could not get to to swap out so I hope it holds out for a while.

My problem right now is when driving the PF, it runs and drives great, except when I accelerate quickly. If I accelerate slowly it does find, but when I hit the passing gear the engine seems to hit a wall, or it hiccups, or stumbles, it feels like the engine just wants to die.

I did check the actuator for the power valve and it is really stiff, I have to move the arm with a screw driver, then it doesn't snap back it just stays where I pried it open. I have asked this question before but no answer. Is the valve supposed to be stiff like that or is it supposed to be able to work easily?

[mdmellott]

There is something jamming up the works. The butterfly valves by themselves, without the actuator arm attached, should be free of any restrictions keeping them from moving. They are a free floating valve assembly. The vacuum actuator has a spring inside. With the actuator arm attached to the valves' rotating linkage, the spring in the actuator keeps the valves closed when there is no vacuum being applied to the actuator. There should be absolutely no stiction in this valve and actuator mechanism.

[BigJim1]

mdmellott, I appreciate you information, that is what I was afraid of, something is stopping that from opening and closing. I will take that valve off and see if it works easy off the truck. Thanks a ton buddy, I will let you know how it goes. Man I hate to have to take that plenum back off again.

[BigJim1]

mdmellott, you were dead on, I went back out there and took the actuator arm loose and it moved freely like it was supposed to. The butterflys were stuck pretty tight. I did move them but still were very tight. I took the plenum back off and sure enough the butterflys had to be moved with pliers. I put some PB Blaster on the shaft where it goes through each and started working back and forth. After a while I could move it with my hand. I kept working it until it was kinda easy but it never was free like it should be.

I put it back together and gave it a try, worked like a charm, it didn't hiccup or hit the wall when accelerating fast. We took it for a spin and abut 6 miles it started losing power big time. Got it back home and the butterflys were stuck open. The gas must have washed all the lube off the shaft. I guess I will take it back apart again and free up the shaft. When I took the screws out and put the Loctite on them, I must have gotten the flaps off a little or something. Anyway, at least I know what it is now. Thanks mdmellott I appreciate it.

[mdmellott]

When I took the screws out and put the Loctite on them, I must have gotten the flaps off a little or something. Anyway, at least I know what it is now.

How did you get the screws out? Mine are so tight, the cross-head is going to cam-out using just a Philips screwdriver and they simply won't budge. While I have the intake off, I wanted to apply threadlocker to those screws but I think my engine may have already had it applied when it was built, given how tight they seem to be.

Is it possible you got some excess threadlocker onto the valve plate shaft where the shaft runs through the body of the intake plenum? That would gum things up a bit like what you are seeing.

[BigJim1]

I don't think I got any Loctite on the shaft, could be wrong though. I put the Loctite on the screws while they were in my hand. I think when I cleaned the butterflies with the MAF cleaner it really cleaned the lube off of everything. As much as I hate to, I will take it back apart again and fix it. I appreciate you help.

[BigJim1]

I am sorry, I didn't answer your question about the screws. My screws were pretty tight and maybe I should have just left them alone, but I have already experienced the screw in cylinder on our grandson's Altima. I didn't want to go that route on this engine so I took each screw out and loctite on each one.

I have looked online to see how much the lower half of the intake with the power valve would cost but so far all I find is the upper half. I am also looking into how to remove that shaft and see why it is sticking. That may be my best way out. One thing is in the back of my mind, and that is the exterior seal on the shaft, if it leaks air, it will spit a code and there ya go.

[mdmellott]

Thanks for the reply. I think I'll just leave those tiny screws alone since it appears they were put in right with the threadlocker at Nissan. As a side note, I noticed that Nissan applied Blue threadlocker to the center two long mounting bolts for the lower intake plenum on my Pathfinder. Nothing was applied to any of the other lower or upper intake plenum nuts or bolts. I'll reapply some Blue threadlocker to those two long bolts when I put it back together. Nissan must have had a reason for applying it to begin with. I can't help but wonder if they skimped out on applying the threadlocker to those two long bolts on the same Pathfinders they skimped out on applying threadlocker to for the power valve screws. Did you notice if your Pathfinder had Blue threadlocker on the two center lower intake plenum bolts when you took it apart?

[BigJim1]

They did have some kind of locker on the threads but it was more white than anything else. Like your's, the rest of the bolts didn't have anything.

What really bumed me out about Nissan is they merged with Renault back in 1999. I never would have bought a Nissan had I known about that. Renault isn't know for quality work and that is probably why there so many problems with Nissan now days.

[BigJim1]

I went out there today with tearing the intake back off and disassembling the butterflies. Just for the heck of it I tried opening the butterflies by hand. Believe it or not they were freed up and worked easily. I worked them several times trying to get them to stick again, they never did stick again. The Deep Creep I sprayed on the pivot points must have soaked in or something.

We decided to take a ride to see if they would stick again, they never did. The truck is running great now. I still don't know why the power valve was sticking, hopefully it won't stick again. We drove about 30 or so miles today so here's hoping.

Now on to seeing what is wrong with the AC, it works part of the time and part of the time it don't.