Just had a shop replace my head gasket, water pump and thermostat. My 06 Monte LT isn't overheating anymore, but now I notice when I'm at a red light or stop sign, the engine kinda "jumps", as in that it's not horrible, but you can notice it doesn't run smoothly, you can feel the vibrations from the inside. The rpm meter will hover a tiny bit. The shop siad they didn't really know what the deal was, to drive it for the weekend and if it still does it, bring it back. Anyone have any ideas what the deal might be? It's really irritating and it did not do this at all before I had it worked on. It's really frustrating because I mentioned it to them before I had it worked on the second time (I had the water pump and head gasket replaced on two different trips there, I noticed this weird idle after they did the gasket, however it was still overheating so I took it back and they found a hole in the water pump)and I mentioned it to them specifially when I took it there, and it's still there although the other stuff is fixed. Thanks to anyone for any suggestions!

 

update: check engine light came on. I think it's misfiring

 

Is it just at idle, or any rpm range. Sounds like maybe a vacuum leak. Got to autozone and get the codes read. I don't know why they would send you on your way thinking it might go away. It usually doesn't. If it ran good when you brought it in, they should make sure its running good when you pick it up

 

If the car was mis-firing the check engine light would FLASH.

It does sound like a vacuum leak to me too. Can you hear a hissing noise when the hood is open?

 

take the car back to them, they should of fixed it

 

Sorry to hijack this thread, but I'm curious. What is a vacuum leak? Where does it come from? And how's it fixed? I only ask because I sometimes think I hear a faint hissing sound from the engine while idling.

 

A vacuum leak would be any of your lines that are vacuum (like brake booster) can come loose and allow the full vacuum to lose some of it's pressure.

To test for it, you just kind of spray soapy water on the area and if it starts to bubble you know air is escaping where it shouldn't.

 

A vacuum leak can come from any lines that come off of your intake manifold. Usually all of these lines are black in color. Some of them are small and hard lines with a rubber boot at the end of them to where they connect to another device such as your EGR valve, Idle air control valve and so on. Another way to have a vacuum leak is if the mechanic did not install the intake manifold gasket (lower or upper) correctly or if they did not apply silicone to the gasket areas.

When you have a vacuum leak the air will be pulled into the engine instead of being pushed out of the engine through gaskets and such. Spraying soapy water may work to help find the leak by observing the section that you spray. You will see the soapy water actually get sucked into the engine and that area will dry up quickly. Another good thing to use is Brake Parts Cleaner. If you spray the Brake Clean around vacuum lines and gaskets you will see that area dry up quicker and you will notice the engine stumble alittle bit because the Brake Clean will get sucked into the cylinders and ignite. I sure hope you understand what I am talking about. I hope that I am making sense. LOL.

Let me know if you need any more advice.

 

Thanks a bunch to everyone. It does sound like a vaccuum leak, because there is definitely a hissing sound when I'm looking under the hood with the engine running. Sounds like someone didn't do something right when they fixed my head gasket. Yeah, why the hell would they just send me on my way, I have no idea how they couldn't notice it, it's clearly not running normal. My girlfriend and another friend of mine said they could definitely feel the difference. I'm taking it back to them Monday and letting them fix it. Rest assured this will be the last time I go to this auto shop

 

also I forgot to mention that when my check engine light came on, it did flash for a bit, then just stayed on steady. However it's not on anymore, but the engine symtoms are still there