I've got a 2003 F-150 with a 4.2 V6. It was running rough and I had a p1518 code. I removed the intake and replaced the IMRC actuator. I cleaned the intake up really well and got all the crud off of the butteflies. When I got it back together and started it, it ran really good and the check engine light went off. When I shut the engine off and restarted it the engine light came back on. I checked it and the p1518 code was back, but the truck runs just fine. I can erase the code and drive it for a long ways and the check engine light stays off. When I shut it off and restart it the engine light comes back on and the p1518 code comes back. I took and endescpoe and looked at the acuator and it is operating just fine when you rev the engine up. Everything is hooked up, but the code comes back along with the check engine light. Does anyone have any ideas that I might have missed.? Thank you, Jim Wilson

 

Check the spark plugs. Signs of oil burning via fouled plugs?

Without knowing anything else (ie, mileage on engine), there’s good chance it’s burning oil and has some blow by forcing those butterflies open. Those butterflies and intake will be pretty crusty if this is happening.

Been there, done that. Start making future plans with or without the truck.

 

Thank you for your response, but the engine is in pretty good shape. It doesn't smoke and it doesn't use any oil, so I've got to believe that there is something else that I'm missing. When I cleaned the intake out there wasn't any oil in it or on the butterflies.
Again I thank you for the answer to my post.
Jim Wilson

 

P1518 IMRC STUCK OPEN, so even though the butterflies seem to be working fine they're probably not closing 100%, thus triggering the code. Double check if the imrc bushings are still there, sometimes they break and fall out.

 

Did you ever figure it out? I am in the exact same situation right now. I took the lower intake manifold off. Cleaned it all up. Bought a new intake manifold runner control arm and installed it properly. The bushings are all brand new everything's on everything's connected and I am having the check engine like come on as well. After everything that I have done. Was there anything you did that made the issue go away?