Cpotts80

So I decided to clean my throttle body because of lack of throttle response and looked inside the manifold and saw it was cracked! I just bought this truck (2006 f-150 5.4 fx4) and the dealer wasn't any help in fixing it so I did everything myself including COPs plugs O2 sensors fuel filter. I did all of this originally to get rid off the misfires which I did but now the cracked manifold. It's cracked horizontally about 2-3 inches down from throttle body. My questions are has anyone seen or had this happen? Can this be causing my poor throttle response and should I buy an oem or dorman aftermarket manifold? Thanks in advance!

F150Torqued

Not exactly the same experience, but did replace my cracked IM. But I would recommend the following: If you DO have a very significant crack (or leak) in the intake manifold, the symptoms should be lean codes on both banks (P0171 & P0174), elevated short term fuel trim on both banks, and poor gas mileage. The absolute sure fire diagnostic method to determine a crack for sure is: Use a live data scan tool and with KOER, then monitor O2 Sensor voltages from both banks - and/or - Short Term Fuel Trims 1 & 2 WHILE pinpoint spraying a flammable liquid (such as carb cleaner, starting fluid, or electrical connection cleaner) all around and under the intake manifold and vacuum line connections.

If you hit a spot where ANY air is getting in post MAF, it will register dramatically on the scan tool readings. Mine would go "NUTS" when I sprayed starting fluid (ether) under the IM on the passenger side by the alternator. New (Dorman) IM and gaskets cured the codes and improved gas mileage about 3 mpg - but I can't say I was ever suffering any loss in throttle response.