Weird sound/feel in Park at idle after driving - 05 3.5

[RedGeminiPA]

I've noticed this within the last couple of days. After driving for a little while, when I put it in park, it has an odd *feel* at idle in park, and I can hear something that is hard to explain. It's almost like an intermittent grunt sound. The first time it did it was after I started it after sitting for about 15 minutes on Saturday, when we were leaving a friend's house on the way back into town.

When we went to my aunt's for dinner and when we got home yesterday, it was doing it again when I put it in park. I popped the hood to see if I could hear it better, but I couldn't hear it at all, really. It can only be heard from inside.

I'm totally stumped. My buddy looked at the mounts a little while back, and he said they all looked good. None looked smashed from the dealer dropping the tranny. We also did the brake/gas torque check to see if there were any odd excessive movements of the engine under load. All looked normal, and we used my '04 as reference.

I should note that I had just got back into town after a 300 mile round trip Saturday. I got gas at the station I always buy from, and I've never had any issues with their gas. I didn't notice this behavior during the trip.

I've also noticed some roughness/shaking when starting and shutting off for about a month or so, maybe a little longer.

No MIL lights. 124k on it. Prop shaft is still out of it.

Any ideas or help is greatly appreciated.

I'm uploading a video now of startup. You probably won't be able to tell the rough starting. I'll post the link as soon as it finishes uploading.

[RedGeminiPA]

I'm having trouble uploading. I'll work on it when I get home this afternoon.

[far2grumpy]

I'll offer an off-the-wall thought.

One thing that happens periodically - when engine is at operating temperature - is EVAP purge valve activates to slurp stored fuel tank vapors from the carbon canister.

You probably should not notice on a V6 if the valve opens and closes correctly. However, if the valve is leaking - the engine could idle rough and may make an unusual noise when manifold vacuum changes with the pruge cycle.

[RedGeminiPA]

Originally Posted by far2grumpy

I'll offer an off-the-wall thought.

One thing that happens periodically - when engine is at operating temperature - is EVAP purge valve activates to slurp stored fuel tank vapors from the carbon canister.

You probably should not notice on a V6 if the valve opens and closes correctly. However, if the valve is leaking - the engine could idle rough and may make an unusual noise when manifold vacuum changes with the pruge cycle.

That makes sense. It would explain why I can hear it inside (above/behind exhaust/manifold) and not really under the hood. Any way to know for sure? Is there anything I can do to rule it out, or confirm it, or fix it?

Here's the video, though this isn't really the problem/sound. This is just startup.
http://www.youtube.com/watch?v=lfi_pryYz40

[far2grumpy]

Originally Posted by RedGeminiPA

That makes sense. It would explain why I can hear it inside (above/behind exhaust/manifold) and not really under the hood. Any way to know for sure? Is there anything I can do to rule it out, or confirm it, or fix it?

Here's the video, though this isn't really the problem/sound. This is just startup.
http://www.youtube.com/watch?v=lfi_pryYz40

Since its just between us ... I'd wait until the issue is happening and then try - temporarily - pinching-off the hose between manifold and purge valve.

I used a hemostat to demonstrate. You could also squeeze right at the manifold exit-port or temporarily remove the tubing from the manifold (plug hole of course).

[RedGeminiPA]

Originally Posted by far2grumpy

Since its just between us ... I'd wait until the issue is happening and then try - temporarily - pinching-off the hose between manifold and purge valve.

I used a hemostat to demonstrate. You could also squeeze right at the manifold exit-port or temporarily remove the tubing from the manifold (plug hole of course).

I haven't had a chance to try this yet... I gotta get a hemostat.

I'm curious... if this does do the trick, what's the next step?

[far2grumpy]

Originally Posted by RedGeminiPA

I haven't had a chance to try this yet... I gotta get a hemostat.

I'm curious... if this does do the trick, what's the next step?

If poor idle is an issue - and purge valve is the culprit - you could swap it.

If the noise is the only bother I could learn to live with it (new valve at RockAuto is $112 - gulp).

[RedGeminiPA]

Ouch... well... I kinda hope that's the problem, but I kinda don't. Know what I mean? At least I'd know what it is.

I'm going to see if I can find a hemostat tomorrow and give it a try.

[far2grumpy]

Originally Posted by RedGeminiPA

Ouch... well... I kinda hope that's the problem, but I kinda don't. Know what I mean? At least I'd know what it is.

I'm going to see if I can find a hemostat tomorrow and give it a try.

You could use needle nose pliers or even vise-grips. The goal is to pinch the hose while the flaky idle and/or noise is occurring. The noise should cease almost instantly once the hose is crimped.

If it does not stop - we can consider plan B (EGR valve), or plan C (pcv valve).

[RedGeminiPA]

Originally Posted by far2grumpy

You could use needle nose pliers or even vise-grips. The goal is to pinch the hose while the flaky idle and/or noise is occurring. The noise should cease almost instantly once the hose is crimped.

If it does not stop - we can consider plan B (EGR valve), or plan C (pcv valve).

Okey dokey. Now, THAT I can do. I'll get my other half to squeeze it while I sit inside and listen.

[RedGeminiPA]

So, yesterday, I was pulling down the driveway, and stopped at the bottom (downhill). I put it in Park, and lifted my foot off the brake. I normally pull the parking brake when on a hill, but kinda forgot this time. When I pulled it out of Park, it made one hell of a bang, and the whole thing shook.

Should I maybe be looking at an engine/transmission mount? Could that be the source of this whole issue?

I got to thinking about something. Before I bought my Red Line, I was talking to a guy who had one for sale in NJ (an '04). One thing he noted was an odd, intermittent, vibration at idle. He said he was told it needed a mount, but never got around to having it investigated further.

I can easily see the one on the passenger side and bottom front on the crossmember. Where are the others located so I can attempt to check them?

Is there a good way to test them, maybe using the engine torque method? Would Reverse be more prominent that Drive? I've also noticed it feels a little rougher when in Reverse - accelerating.