2005 Mercury Grand Marquis - 4.6L P0171/P0174

Specific repair issues for Ford cars & FWD vans
Post Reply
HINEMANS
Member
Posts: 21
Joined: Wed May 14, 2008 11:53 am

2005 Mercury Grand Marquis - 4.6L P0171/P0174

Post by HINEMANS »

long term fuel trim 30 both banks +12-16 short term smoked motor and found no leaks. plugged pcv ,brake booster and evap with no change. fuel pressure is about 45 lbs running or engine off. tried a mass airflow and fuel pressure sensor cant find anything I usually see .. what am I missing help. car has been around the block a few times would like to have the answer by the way 86000 miles with a 4.6l
User avatar
steven kiser
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 6184
Joined: Fri Jul 06, 2007 4:58 am
Location: eastern ma.

Re: 2005 mercury grand marquis p0171/p0174

Post by steven kiser »

With the scanner attached look at the engine temp. If it's not reaching operating temp it can cause issues like this and for some reason even though the low temp should throw a code with the year and mileage it may be only used for short hops and have developed a carbon contamination issue. I've seen plenums and valves so loaded with carbon that after driving for a bit it gets soaked and starts dripping raw fuel into the mix. The B&G cleaning system works best or the Snap On Tools injector cleaner. Now the second issue is even when the problem is resolved the KAM needs to be reset and it will take a while. We usually take them on the interstate and blow them out then drive at 50 for 20 minutes, get off and drive at 35 for 20 minutes. Make sure the pintle on the IAC is clean along with the seat. Even after the KAM is set the vehicle may act a bit off or strange for a while. Another thing I look at on Fords of this vintage is converter back pressure. If it's been running this way for a long time the cats may be restricted. Take the pressure readings at a high rpm. If it were in my shop and I found a restriction I would call customer for a face to face and include using the car to point and show of why the cat's are restricted. Problem here is so many cooks have been at the pot it's dog food by now and the customer expects a 5 course meal including Duck and Veal.

Have the 02's been replaced with the correct ones? Are they OEM or are the ends spliced on? I believe if this is a flex fuel system (very rare) the sensor on the fuel pump may be malfunctioning and the PCM thinks the fuel has a higher alcohol content than it has. I think the sensor is at the pump, could be incorrect. The key is looking at all the readings through the scanner. It's old enough for dried and cracked wires.
never argue with a fool, they'll drag you down to their level and beat you with experience
Post Reply

Return to “Ford Cars”