Last year I had some repair work done on my car, and immediately after that the car started experiencing strong vibrations when in Drive or Reverse but standing still, and lesser vibrations when in park.
The work done was that they replaced the valve cover gasket, the exhaust manifold gasket, and the catalytic converter (with a kit). The vibrations started immediately after that.
I brought the car into several shops, but no one can figure out where the vibrations are coming from. The engine mounts are all good. The spark plugs are good. There don’t seem to be any symptoms of a rough idle. And the car doesn’t lose any power. So it’s very strange.
Yesterday I had my spark plugs changed and the guy accidentally disconnected the brake booster vacuum hose. With that disconnected, the vibrations were almost gone. Still there a little, but faint. After the reconnected the vacuum hose, the vibrations were back strongly.
So this seems to be a clue as to what’s going on, though I don’t know what it could be.
Any ideas of how the vacuum hose and braking system might be connected to the strong vibrations I’ve been experiencing?
Yes, correct. That thread had gone on for so long, I figured I’d start a new thread with just the relevant facts, rather than tacking it to the end of that super-long thread.
@TwinTurbo makes an important point about whether or not the brake booster hose was plugged after being removed from the booster. That hose has a large diameter & goes directly to the intake manifold. Any air leaks will result in a too-lean mixture. It and everything it connects to must be air-tight. The hose and the booster where the hose connects should also be checked for signs of brake-fluid contamination. The PCV system should also be verified to be functioning properly.
If the engine idles better with that hose removed from the booster and not plugged , that’s a different kind of mystery. I’d expect a warm engine to idle very poorly or even stall in that configuration.
One further possibility: Are there any signs of leaking at the valve cover, exhaust manifold, or exhaust system interfaces that were affected by the prior work?
It sounds to me like your IAC (idle air control) valve is bad. The extra air allowed into the engine when disconnecting the brake booster line is compensating. Make sure they didn’t disconnect the electrical connection/pinch a wire when doing the other work.
After the valve cover gaskets were replaced I still had a leak coming from somewhere. I had them check when they changed the spark plugs. They said they didn’t see any leak, but that there was a bunch of dried gunk from past leaks that he sprayed with brake cleaner and wiped off. Said it left a puddle on the shop floor. So that should have taken care of it.
However, I do still seem to have a small leak of something that seems lighter than oil. Could be transmission fluid, as I’ve had leaks with that in the past.
I know that the A/C high pressure valve was leaking and they replaced it and refilled with freon. They said there weren’t any other leaks in the A/C system.
So, basically, you’re saying (if I understand you correctly) that this may be a red herring and the loose hose may have just caused the engine to idle more quickly, diminishing the vibrations?
Yes, when the idle speed is increased, the engine will be smoother. Engine idle speeds are generally as low as practically possible for reduced fuel consumption, the compromise is idle quality.
If you are feeling excessive engine vibrations, your replacement engine mounts aren’t up to your standards or the new exhaust pipes are transmitting engine vibrations to the vehicle body.
Those were the first things that came to everyone’s minds who looked at it. And every shop/mechanic said the mounts are fine and they didn’t see anything wrong with the tail pipe (though I admit the tail pipe seems a likely culprit, given that the vibrations started IMMEDATELY after it was replaced!).
In fact two of the engine mounts were even replaced in an effort to deal with the vibrations. No change.
I agree that it seems to be tail-pipe related. But so far no one has found anything.
Maybe I should go to a muffler shop and get their opinion? I mean, they’re kind of the tail pipe experts.
Exhaust pipe. The new catalytic converter has an inlet and outlet exhaust pipes, the tailpipe is at the rear of the vehicle.
Inspecting these things will not show obvious problems, your grease monkeys probably inspected for “broken” engine mounts, a coarse idle is usually cause by hard, collapsed engine mounts.
Two out of three engine mounts were replaced and prove to be no better than the old mounts, where were these purchased?
The catalytic converter was replaced with a kit that included the tailpipe.
So, do you think it’s advisable to go to a muffler place to have them inspect it?
If an engine mount was collapsed, wouldn’t they have noticed it?
The shop that did the original work replaced the front and rear engine mounts while trying to diagnose the problem. They said the side engine mounts were fine.