2007 3.7L 185,000 miles.

I found out that my intake manifold is cracked. I had my throttle body off to clean it, took a look inside the manifold and noticed a crack at the back lower wall. I cannot see it from the outside.

My first question is compatibility. It appears that '06 and '07 are the same manifold, but '08 and on are different. Can someone confirm?

Second, I have been struggling to find the source to a problem where shortly after the first start of the day, the engine stumbles for half a second, catches and continues on just fine for the rest of the day. I recently was able to confirm the stumbling happens during the switch from open loop to closed loop. Could an air leak cause this symptom? I have performed most all of the other "fixes" for the stumbling problem (plugs, throttle body cleaning, oil change, intake bolt check, MAF cleaning).

 

My guess is your stumble was a dirty TB. If your Intake Manifold was cracked and leaking, you would know it by the CEL, poor fuel economy, even misfires etc... What you think is a crack is probably the Mold Mark when the plastic was injection molded. Look at it under very bright light and if light is not showing through the other side, no leak. They do not just crack. Highly unusual.

Pull the camshaft actuator solenoid and look for crud on the sensor, on the screen in the motor, or a missing screen... replace if necessary, tighten mounting bolt to 10 N.m/89 lb in.

let us know what you find.

 

Even if the plastic was cracked you could fuse it back together with some metal mesh screening and a soldering iron. Then coat the outside with jb weld or the like. This is really odd though as was stated above.