Manager Forum

We have 1996 Lincoln Town Car with 4.6 Engine.

Code p0174 both fuel trims at idle are moving 3+ to 3- on both banks. When driving, it jumps on both banks to 30 to 40+ trims. We check for vaccum leaks with propane and egr tube and clean mass air flow sensor; readings are in spec by ford specs. The o2 sensors are switching evenly on both side engine runs very good and no missing and good power.

Has anybody ran into this problem before?

seen maf's cause it. ford maf's can be within specifications and still be bad.

Agreed. Sounds like a bad MAF.

Check the MAF at WOT, take a snap shot on your scanner or have helper watch it. With a 4.6 when it is at 3500 RPM WOT, you should see around 129 grams of air flow per second. You will prob see a figure closer to 100 or less. this woud def indicate a bad MAF.

Easy MAF formula: engine RPM in thousnads ( 3500 = 3.5 ) times engine size ( 4.6 liters) times eight (8). This will tell you if it is working correctly. If your are way above sea level these numbers will be a bit lower.
THIS IS FOR NATURALLY ASPERATED ENGINES ONLY, NO TURBOs OR SUPERCHARGERs.

The fix was the mass air flow sensor Thank You for your help. Ray

thanks for posting the fix. speaking for myself, it means a lot when someone closes a post.