The vibration may be an engine misfire symptom. Usually this would turn on the CEL, but sometimes it takes several drive cycles before the warning light on the dashboard turns on. Ask your shop to check the computer memory for pending diagnostic codes. Not something to be ignored or deferred b/c engine misfires can damage the catalytic converter.
As far as whether replacing the gaskets is the cause of the vibration, as long as there’s now loud banging exhaust sounds, seems pretty unlikely to be a gasket installation or re-torquing problem. But it could be that something else was left disconnected or not properly buttoned up afterward. The shop probably has to remove a bunch of stuff that’s in the way as part of the gasket job.
I think it is a good idea to re-torque the exhaust manifold gaskets every once in a while, but 100 miles seems too soon. Maybe every 6 months to a year, 5k/10k miles.
Lets end this flame war. @enargins, you don’t have to respond to every negative comment you receive. In fact, if you are not careful, the cyberbabes will kick you off. Better to be like a duck and let the water just shed off your back.
@Mustangman, I feel your frustration when you give good advice and it gets ignored, like they didn’t even read your post. I kinda wanted to give the OP of the Mustang not starting post a verbal dope slap, and I did but it was a light one. I believe I was the first to suggest the start ignition wire but I gave him a simple test to be sure. Now a hundred posts later, everyone is still arguing about that stupid little wire and the simple test still hasn’t been done. It’s hard to hold back, but you do get a little harsh on some of the posters once in a while, even though you do often give good advice.
Life gets a lot easier if you let it go. If someone cannot affect your paycheck, their opinion of you does not matter.
BTW, if the shop comes up with a legit reason for the vibration, especially if it is one that has been suggested here, you might want to give them a second chance. You could go from the frying pan into the fire.
OK, you are not listening. Mustangman has been a member in good standing here for a long time and generally gives good advice. We all know how he can get occasionally but you are alienating more than just him here. Please listen to me and let it go.
The first thing I would check for is an air leak, hose that came off or old and not a good seal.
At least that was the problem with the 61 lark 50 years ago. Ran terrible, vibrated, etc. about a 5 minute job including opening the hood and trimming the end of the hose by a smart aleck college kid.
So, I spoke with the service manager. He said they didn’t have a chance to look at it in detail today. Said they’re going to put it up on the rack tomorrow and take a closer look at it.
But he said he looked at it quickly with a flashlight from the top of the engine, and he said that the engine mount that’s next to the exhaust manifold looks like the rubber inside of it is misplaced, and it could be metal on metal, which could be the source of the vibrations.
He said that he could definitely feel the vibrations when it’s in gear. When it’s in Park, it feels normal (small vibrations). But when it’s in Drive or Reverse, you can definitely feel the strong vibrations. He said that seems to indicate that it’s an engine mount. But they’re going to look at it more closely tomorrow.
I asked why I didn’t feel that before. He said it’s possible that when they were messing with the exhaust manifold that they knocked it, and the rubber got pushed out of place. He said that’s the only thing that makes sense to him.
Also, I asked about possible misfire codes, and he said they checked the live data while it was running, and there were no misfires.
I asked him about the possibility of it being an air hose leak, and he said they’d check for that tomorrow.
The check engine light will flash while the engine is a misfiring, then remain on for the duration of that ignition cycle, you would have noticed that while driving a night.
Just spoke with the service manager. Said they checked the fuel trim and it was spot on, between 1.8 and 2.5, so he didn’t think there was a vacuum hose leak.
Said they checked the engine mounts, and only the front one, next to the exhaust manifold, seemed bad. So they went ahead and replaced it.
Said they’re taking it for a test drive now, but so far everything looks good.
So, I guess the manager spoke too soon. The vibration is a little better, but not much. The small vibration that was there when it was in Park is completely gone, and back to how it was before. But the large vibrations when it’s in Drive are still there, though a little better.
Previously, the Drive vibrations were so bad you’d feel them in your body when your hands were on the steering wheel. Now that’s no longer the case, but the steering wheel is still vibrating very bad.
On a scale of 1 to 10, if the previous vibrations were a 10, then they are now about a 7.
The service manager said he didn’t know what else it could be. Said the side mounts both looked good. Said he wasn’t sure about the rear mount, though.
He said they’ll bring it back up on the lift and double-check the mounts, especially the rear one. He said the rear one is really the only other one that could be the issue.
So he’s going to let me know what happens once they recheck the mounts. Other than that, he said he doesn’t know what it could be.
