Usual suspects confirmation - slight engine shake at idle

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getdealtwith

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OK, so I thought I'd circle back here to report that I found that the vent line from the driver side valve cover wasn't plugged into the elbow piece right at the valve cover. The random shaking is 80% better now but not completely gone yet. I'll replace the pretty rotted hose along the firewall next and will check the motor mounts as well. Thanks for the support everyone!
 

TobyU

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OK, so I thought I'd circle back here to report that I found that the vent line from the driver side valve cover wasn't plugged into the elbow piece right at the valve cover. The random shaking is 80% better now but not completely gone yet. I'll replace the pretty rotted hose along the firewall next and will check the motor mounts as well. Thanks for the support everyone!

So that was a pretty big vacuum leak. A good way to hear those is to take a 4 ft piece of rubber hose like 5/16 or 3/8 and put one end in the edge of your ear and run the other end around everything the engine you will hear the leak.

Also the fuel trims on a scantool should have been high since vacuum leak.
 
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getdealtwith

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So that was a pretty big vacuum leak. A good way to hear those is to take a 4 ft piece of rubber hose like 5/16 or 3/8 and put one end in the edge of your ear and run the other end around everything the engine you will hear the leak.

Also the fuel trims on a scantool should have been high since vacuum leak.
Excellent idea. I'll have to try that next time.
 
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I have the slightest of vibration at times when idling, engine runs great, no codes, noises, etc. Assumed it was mounts and planned to inspect when I do an oil change here in a couple weeks. I've had other vehicles exhibit similar behavior. I'm sure they are still present when driving bit it's so subtle you cant tell over the rest of the movement.

Did you end up replacing your motor mounts? Did it make any difference?

My mechanic found several other damaged vacuum lines - incl. some that only revealed themselves when he replaced the intake manifold. During that job I also had him install new Motorcraft plugs and coil boots along with injector o-rings. The last bit (PVV elbow), I installed tonight, along with a new PCV valve.

A slight engine shake remains but its rhythmic now. It is present with the AC off or on (off, the engine idles at 780 RPM) but it's noticeable enough for me to want to keep looking even though it may end up being a case similar to Toby's Crown Vic.

One other observation is that there's no difference in the engine shake between P and D or R which I heard may point to a bad motor mount.
 

RichardH

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Did you end up replacing your motor mounts? Did it make any difference?

My mechanic found several other damaged vacuum lines - incl. some that only revealed themselves when he replaced the intake manifold. During that job I also had him install new Motorcraft plugs and coil boots along with injector o-rings. The last bit (PVV elbow), I installed tonight, along with a new PCV valve.

A slight engine shake remains but its rhythmic now. It is present with the AC off or on (off, the engine idles at 780 RPM) but it's noticeable enough for me to want to keep looking even though it may end up being a case similar to Toby's Crown Vic.

One other observation is that there's no difference in the engine shake between P and D or R which I heard may point to a bad motor mount.

Hmm, interesting on the P, D, R.

I have a very slight engine shake - no codes, good mileage. I know for sure if I put it in N the slight shake goes away. Need to observe in P. Also noticed it's 100% smooth when cold, but at operating temp it's got the slight shakey in D. Very slight and I'm being super nit picky over it. It does go away in N as mentioned.
 

Aspen03

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I didn't, I ended up having quite a bit to do that day, slid under the truck and did a quick n and out job. I'll try and get back under there tomorrow or the next day. Its very subtle and nothing that is imparing drivability so it hasn't been a big concern. Mileage is good, no issues starting, idling, etc. Obviously it needs dealt with before it does become a larger issue but its been lower on the list than a few other things atm.

I get to play w the vacuum lines on the navigator soon so that'll give me an idea of what to expect on the expy I imagine. I discovered some things re routed in there and may be part of the blame for the ac shifting from panel to dash vents under load. I printed off all the vacuum routing diagrams in all data so I can just start from the top.
 

Aspen03

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Hmm, interesting on the P, D, R.

I have a very slight engine shake - no codes, good mileage. I know for sure if I put it in N the slight shake goes away. Need to observe in P. Also noticed it's 100% smooth when cold, but at operating temp it's got the slight shakey in D. Very slight and I'm being super nit picky over it. It does go away in N as mentioned.

Mine is essentially this. Very slight. I drive this 50 miles a day, sometimes in total silence just because I want some peace and I notice little things when I come to a stop or happen to be sitting in the lot at work for a couple minutes before leaving. Fwiw I've been in brand new vehicles that have more shake at idle than this.
 
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I know this (fortunately) isn't a 3V motor but has anyone experienced a rougher idle before their timing chain tensioners or guides failed?

What about pulley or belt replacements that made a noticeable difference?

I'm also still interested in any cases where new motor mounts actually fixed slight engine shakes when no other symptoms of bad mounts were present.

Appreciate the input!
 
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nema100

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I'm noticing what I would call a very slight shudder at idle - smooth for a few seconds, then a shudder, then smooth, never under acceleration. I thought I felt something before, but the reason I truly noticed was due to the right passenger seat headrest. It would vibrate with the shudder making a noise. Certainly can feel it now that I'm attuned to it.
 
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