2000 Oldsmobile Intrigue. 3.8L V6. Replaced Intake Manifold Gasket replaced a few weeks ago.
Question: Check engine light came on and car began to run rough after I had the intake manifold replaced on it. Was told by another mechanic that vacuum hoses were broken and one needed repaired. My question is, could this be from the intake manifold gasket being installed wrong?
Answer: It is possible that the job was done incorrectly. To replace the intake manifold gaskets, basically the entire top of the engine has to come off. I have also seen the incorrect gaskets installed. This causes several different problems. That job includes removal of many vacuum lines and hoses. It is very possible the mechanic broke one or more, especially it the car has a lot of miles on it. The hoses and lines would be quite brittle and break easily. Most of the time the mechanic would not even know one broke during the installation.
You did not mention if repairing the hoses fixed the car. If it did not, then you need to get the codes scanned from the computer. This would give an idea as to what is having a problem.
A common thing i have seen after doing the intake manifold gaskets in the 3800 engine is that an 'O ring gets left out of the PCV valve. This causes high internal engine pressure and can cause a rough idle, check engine light, and makes the engine to burn oil at an alarming rate.
To test for this condition, remove the oil fill cap and see if the engine start to run different. You will also feel the engine sucking the cap back on as you try to remove it. This is a tell tale sign of the 'o ring problem. This would make the engine burn oil very quickly.
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