Oldsmobile Intrigue Runs Rough After Intake Gaskets Replaced

2000 Oldsmobile Intrigue. 3.8L V6.
A mechanic replaced the Intake Manifold Gaskets. They were changed a few weeks ago now the engine runs rough and has a check engine light on all the time. I think it was a lean condition code.

Question:
The check engine light came on and my Oldsmobile Intrigue and then the car began to run rough after I had the intake manifold gaskets replaced on it. I was told by another mechanic that vacuum hoses were broken and one needed to be repaired. My question is could this be from the intake manifold gasket being installed wrong? Would broken vacuum lines cause the engine to run rough? Would the shop have to pay for any repairs if they messed it up?

ANSWER:

Yes, that would cause the engine in your Oldsmobile to run rough. Most likely the engine run bad at idle but not so much noticable when driving at higher speeds or accelerating. If it does it through all RPM ranges, then i would look at an ignition system problem like broken spark plugs or plug wire. This would also cause a check engine light code P0300. 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. Not to say it was not done right but maybe the mechanic accidentally damaged a vacuum line.

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 vacuum leak would cause a P0171 lean condition and a misfire would cause a P0300.

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 burn oil at an alarming rate. This is very important to check so engine damage does not occur.

To test for this condition, remove the oil fill cap and see if the engine starts 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.