Fuel damper woes

[atraudes]

So, for the past few months I've been tracking down a problem on my QX4 where the idle is really rough and starting the engine is harder than usual when it's warm. I ended up narrowing it down to the fuel damper, which was leaking gas out of the vacuum port. Fine, no big deal. It's < $100 part and pretty simple to swap out. The problem is I've gone through 4 dampers now, and all are DOA. The first was from Napa (Echlin), two from Amazon (Standard Motor Products aka SMP), and one from courtesyparts.com. All four have had the same stamped markings and part numbers on them, so I'm presuming they're all SMP.

A while back I had the same problem with my fuel pressure regulator and ended up having to replace it as well, and the first unit I replaced it with was also defective. The manufacturer was Echlin again. So far the one that's in there now has been working for 6 months or so reliably.

The really bad news came today. The one I got from the dealership worked beautifully for the first day of driving, then crapped out again. I contacted them about a replacement or refund and they replied by saying they wouldn't warranty the part (basically I was SOL). Their justifications were that they've never had a report of problems with the part and since I've had more than one die it's likely something wrong with the vehicle or the gas I'm using Other than this problem, the car's running like a top and I only use 92 octane Chevron gas. The only modification I've made to the engine is a K&N intake. Their suggestion was to take the car in to get it looked at.

What gives? Is there any validity to what they're saying? Short of having a vacuum far beyond what the spec is, I can't imagine anything that could be damaging it (I'm going to hook up a vacuum gauge later today to see what it actually is). Is there anything else I'm not thinking about that I should be looking at? The fact that the pressure regulator (and everything else) is now chugging along happily is pretty telling, I think.

For reference, my fuel pump, filter, lines, injectors, and pressure regulator are all new (replaced within the last year). The technique I'm using to determine whether a unit is bad or not is smelling the vacuum line immediately after driving. All of them have left the hose reeking of gas, and yes, I've cleaned the hose with brake cleaner and let it dry thoroughly between each test. The pressure regulator's vacuum line doesn't smell at all.

No codes are being thrown. Thanks for any insight in advance!

[atraudes]

Oh, I should also mention that I hooked up a catch can last night to its vacuum line to determine exactly how much fuel is coming out (as well as keep it out of the intake and as irrefutable proof there's a problem). The drive into work this morning was a lot smoother than usual, though I didn't see any fluid in the can. We'll see what happens over the next few days, I guess.

[4xq]

Hard to be sure here Atraudes - if the damper is not visibly leaking fuel, and is not making noise, it is pretty much considered good. I was thinking catch can when I read your post, so I think you are on the right track - just see if there is a visible fuel leak.

I haven't seen one of these torn apart - it may be the design has enough tolerance (aka "slop") in it that there is going to be some fuel smell. There is an Airtex brand on Rockauto which I think they make, not just a rebrand.

If you have a fuel pressure gauge, you might just verify your fuel pressure is ok, as in not too high. But with all those new parts I would guess you are ok.

[atraudes]

Thanks for the reply!

You may be right about this being within an acceptable margin of error. For now I'm going to work under the supposition that it isn't, but I'll be keeping that in mind as I continue. At some point I'll have to assume as much

I don't have a fuel gauge hooked up any more, but I had one spliced into the original damper's hose for a few months because I was troubleshooting a fuel pressure issue (the failing pressure regulator). Once I replaced the regulator, the pressure was on mark every time I looked at it, so I'm guessing that's not the problem. I did hook up a gauge to the manifold and it was rock steady at -22 psi at idle, and ducked down to 10-15 when revving. I didn't try WOT.

I considered trying the Airtex off Rockauto, but I'm a little concerned that they wouldn't be up for returns the same way courtesyparts.com did. The photos there don't show the same stamping on the top though, so that's promising! Sadly, the only other brand I can find that makes these things is BWD (Borg Warner) which is available from O'Reilly, but it's a special order part for them which equates to an additional charge plus a few weeks of wait time since they have to get it from the manufacturer. I think at this point I want to try a couple more from Napa and see if I can come up with a good egg since they're so cool about returns.

I checked the catch can after getting home and even pulled the hose off for a few seconds with the engine running to clear the lines, and it was still dry The new hose I used next to the damper did reek of gas though. I wonder if it's leaking tiny droplets or something...

I also called SMP this afternoon but they weren't able to tell me anything I hadn't already heard. They also said they hadn't heard of any failures or problems. The guy I talked to did say something interesting though: they don't manufacture these particular parts themselves. They actually get them from Nissan and resell them under their name, not the other way around!

Sorry for the long posts; I'm having to re-evaluate my understandings and presumptions and these brain dumps help sort things out a bit and give folks the opportunity to call

[4xq]

Still having idle issues? That is excellent engine vacuum.

[rgk]

I recommend tracking down a used OEM, known-to-work damper. If it fails soon after you install it, you'll know that the problem is somewhere else within your fuel system.

I see one available on eBay: http://www.ebay.com/itm/01-04-Nissan-Pa ... ee&vxp=mtr

[atraudes]

Hm, that is an idea...that price though! Brand new ones are cheaper Trailer hitches have the same problem on eBay! I have been looking for an excuse to head to a pick-a-part place.

[rgk]

For me, the pick-a-part is not an option, and I've discovered that online used parts vendors will accept most reasonable offers. I LOVE seeing that "Make An Offer' button!

[rgk]

Also, the eBay option offers some sort of guarantee that the part is in working condition. Pick-A-Part, who knows?

Don't get me wrong, though. If there was a junkyard nearby with Nissans in tow, you'd see me there.