Just recently, P0174 and P0171 showed up on my "04 STX Heritage (102K miles). Engine running rough in the early morning. At stop signs or red lights it starts to sputter like it wants to cut off until it warms up for the day. I have changed MAF, then the PCV. Now I want to change the O2 sensors (Frt & Rear) to see if that does anything.
I've noticed when engine wants to cut off, it sounds as if the air is getting choked up. I've also changed the air filter and the same result. Another thing I don't understand is Bank 1 and Bank 2 which is lean or rich. I am tempting to replace EGR valve or the gasket, or spray WD-40 around vacuum hoses(while engine running) to see if it revs. Can I get some insight from someone.

 

i would suspect a vacuum leak too. check youre vac lines again

 

I ran into the same problem a while back around the same miles as yours. Below is what I did to correct the problem. I purchased all parts from Ford for about $190.

- replaced plenum gasket.
- replaced upper and lower intake gaskets.
- replaced EGR gasket.
- replaced the PCV hose near the passenger side firewall.
- replaced isolator bolts on the plenum.

 

Don't waste your money on new O2 sensors, yours are fine - they are doing their job and reporting an uncorrectable lean condition almost always caused by excess air being introduced after the MAF - i.e. a vacuum leak.

 

i'd say make sure the IAC is in good shape, check the voltage going into it and make sure it is in spec. I've had several problems with my vehicle and others that were solved by replacing the IAC valve.

 

want to sell your valance?

 

Thanks for the guidelines. Will be working on it this weekend in the cold. I will not do the O2 sensors but will try the rest.

Thanx

 

Are you talking about the Idle Air Control?

 

Correct.

 

Went to Ford part counter and they gave me the elbow that tends to be the culprit of the rough idling. But for some odd reason I can't find where it needs to go. He told me to look under the IAC but found out in other threads that it goes to the rear of the passenger side by the firewall.

I replaced the tube that goes to the valve cover to the PCV and made the engine sounds a little better but still choking at cold operations. Where does the elbow go (PN: F65Z-6762-CA)?

 

I'm fairly certain there are two locations of that "elbow". I believe the one you're probably not seeing is on the passenger side, behind the intake on the top back passenger corner. Feel around back there for it as you can't really see it from a front view.

 

Ok, replaced it but still running rough. It looks like I will have to go deeper into the repair. I am going to cough up $145 for the Upper and Lower Intake Manifold gaskets. The parts counter guy gave me a copy of the Intake Manifold steps to replace it.

Here are the steps if someone else needs to do it:

Removal
1. Remove the upper intake manifold.
2. Drain the cooling system.
3. Disconnect the throttle position (TP) sensor. <Above EGR>
4. Disconnect the brake booster vacuum hose. <Right side of intake manifold>
5 Disconnect the vapor management valve (VMV) hose. <Under throttle near cable>
6. Disconnect the positive crankcase ventilation (PCV) hose. <Middle hose>
7. Disconnect the heater water hoses. <2 other hoses on PCV>
8. Remove the heater hose bracket at the intake manifold. <Left side of intake manifold>
9. Disconnect the intake manifold vacuum connector.
10. Disconnect the EGR solenoid electrical and vacuum connectors.
11. Remove the eight (8) bolts and intake manifold spacers assembly.

Installation

1. Inspect the intake manifold spacer assembly mounting gaskets. Install new gaskets. <6 total inside>
2. Install the intake manifold spacer assembly. Tighten bolts in two (2) steps in sequence.
The front of vehicle is at bolts 3 & 7, the firewall is at bolts 4 & 8.

3 1 5 8

7 6 2 4

Step 1 - Tighten all bolts to 6 Nm (53 lb-in) then
Step 2 - Retighten bolts to 10 Nm (89 lb-in)

Reverse removal step to put it back together.

These were the steps off the Workshop Manual. Good luck. And as a backyard mechanic...I gonna need it.

 

I have a 99 navigator with the 5.4 dohc. I just replaced both the intake gaskets as the intake needed to be removed to install the engine in the truck. The manual I had told me to tighten the bolts to 10 Nm and then turn each bolt an additional 90 degrees. I am getting the same lean code as you and am unable to find a vacuum leak anywhere. I damn near cleaed everything off spraying so much starter fluid looking for a leak.

 

Good luck. That should take care of your vacuum leak\rough running issue. I had to do the same to my truck after doing the small items just as you have. I had a buddy of mine help me (who is mechanically inclined) and we knocked it out in a few hours. My truck ran great after those intake gaskets were replaced. I was also give new "isolator bolts" to fasten to plenum. Apparently there is a TSB for those needed to be replaced\updates.

 

I too have had this happen, twice and the solution is simple. Unbolt your coil pack and turn it over. You'll find a crack somewhere on the bottom. I've had to replace two of them. Aftermarket or Motorcraft same thing. Moisture gets in while the truck sits overnight and shorts out the coil. After it warms up to temp it cooks the moisture out and it acts fine rest of the day.