My 1995 volvo 960 with about 125k miles has a rough idle after the engine has warmed up (after a couple of minutes). When you apply gas to rev the engine over 1500 the rough vibrations go away.

The check engine light came on and I got a 2-3-2 code (fuel trim too lean at idle). I am guessing it's a bad O2 sensor or the wiring but wanted to check if there are any other possible causes for this. I did a quick inspection in the engine compartment and under the vehicle to look at the sensor and wiring and they seem fine.

 

Sounds like you have a leaking intake manifold gasket. There are a couple of ways to diagnose using propane gas. A bad intake gasket would not be uncommon.

Also you might try and be sure the fuel pressure regulator is not leaking fuel into the manifold.

DanR '94 964 356,000 (122,000 on the new engine)

 

Just wanted to post an update on this issue. I started noticing that the engine idle was getting rough right when I started it up cold. So I took it to a shop and they found a leak in the intake manifold gasket at the rear of the engine. It was replaced and now it runs smoothly again.

 

Is this a costly project or could a weekend warrior take intake replacement into my own hands?

 

Had the same issue with my 94 960 leaking manifold gasket #6 cylinder. Replacing the gasket was pretty easy about 2.5 hours. you need long 1/4 inch extensions.

 

replaced intake, same issue, any help