98 2.5 p1506, p1401, p0303

[nestico18]

Hello everyone, well i'm new to this forum. I figured this is the best place to come for specific help on this subject. I have a 98 2.5 with a 5 spd. Has about 155k on it. I had someone read the codes for me and the three i have listed above were pulled. 1506 is i believe high idle, The typical hard to figure out 1401 DPFE, and 0303 which is cyl 3 mis fire. I love the truck and is my everyday driver to and from work everyday which is 45 minutes one way so i need to get this problem solved which is why I started my own thread compared to looking through every single post and trying to narrow it down. When i start my truck it sounds like its missing and idles rough. When you rev it up in neutral it seems fine. In gear pulling out it feels like it hesitates and bucks like it doesn't wanna go anywhere. I dont understand it. Also it seems like it wants to stay idling at about 1200rpm which seems higher them normal. I know a lot of people have this problem and replace a lot of different things and still can't figure it out. Does anyone know if some of these codes are related that one problem is causing all three codes. I have brand new plugs and wires on which are all motorcraft. I'm hoping someone can steer me in a more specific direction. I'm not a mechanic but i'm not stupid either. I had a problem with this truck before and ended up pulling the motor and had to put a reman cylinder head on it with all new top end gaskets and it ran just fine after that. I did all the work myself so I would say that I atleast know how to mess with things enough to get by. Hope someone can help me out. I need to get this fixed being it's my only vehicle.

 

[XLTsplash]

I would start by fixing you P1401. Ford did have a lot of problems with the DPFEs and they even had a TSB and updated parts to fix them.
1,200 is too high for your idle speed. You can unplug your IAC and see if the speed drops. Do you have any vacuum leaks ?

 

[nestico18]

I am replacing the DPFE after work today. Got a motorcraft replacement. Also got new hoses that run to is aswell as a new egr valve and gasket. I don't believe I have a vacuum leak but also not sure how to track one down if I were to. I'm goin to try and un plug the IAC if I can find it. Is it something I can just leave unplugged it is that just to see if it's bad. I'm sorry, I'm not good with electronics thus why I'm here in this forum ??

 

[WarHawk-AVG]

I would start by fixing you P1401. Ford did have a lot of problems with the DPFEs and they even had a TSB and updated parts to fix them.
1,200 is too high for your idle speed. You can unplug your IAC and see if the speed drops. Do you have any vacuum leaks ?

P1401 Ford Description

The purpose of the Exhaust Gas Recirculation (EGR) system on your engine is to limit oxides of nitrogen (NOx) emissions. This is done by redirecting small amounts of exhaust gas back through the upper intake to get mixed in with the air/fuel charge. The resultant diluted air/fuel mixture (i.e., less oxygen per cubic foot) burns cooler and combustion chamber temperatures are reduced accordingly, thereby lowering NOx emissions.

The Ford DPFE/EGR system is controlled by the Powertrain Control Module (PCM). The system employs an EGR Valve, an Electronic Vacuum Regulator (EVR), and a Delta Pressure Feedback EGR sensor (DPFE).

The DPFE Sensor measures EGR flow across an orifice located inside the special EGR Tube. The orifice is positioned between two hose ports coming off the tube which are connected to the DPFE sensor with special heat-resistant hoses. When the EGR Valve is open, a pressure differential is created across the orifice (intake manifold pressure vs. exhaust pressure). By design, this difference in pressure is measured by the DPFE sensor in terms of voltage. The DPFE voltage signal output to the PCM is directly proportional to the flow of exhaust gas entering the intake manifold.

oooh...the EGR valve...bleh

You can pull the old one off and clean it out if it's just gummed up...

P1506

P0303

Yeah if the EGR valve and idle air control stuff is acting squiffy...that is the biggest cause of everything else

I have seen checking for vacuum leak, listen for hissing

 

[XLTsplash]

The IAC is on the back side of the throttle body, mounted with two bolts .I would just unplug the IAC connector when the engine is warmed up and running at idle to see if it's causing your high idle. The IAC can get dirty and stick. They can be cleaned with carb. cleaner. Or you can just replace the IAC. If you remove it just to clean your old one you will probably need a new gasket for the IAC.

If you install new parts then disconnect your battery, not only will it clear your codes the PCM will also have the relearn idle strategy with your new parts. If you don't hear a vacuum leak, you can check for one by spraying carb. cleaner around the intake, vacuum line and hoses. Keep the spray away from exhaust heat. If you spray something that's leaking you will hear a change in engine speed.

 

[Mazda]

Check out this site to help you solve your problems. Also I would pull your Cyl. 3 plug and make sure its not cracked.

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1


Bryan

 

[nestico18]

So last night I replaced the DPFE and the IAC valve. Could not get the egr valve off but I unhooked the battery for a while and started it back up and it actually idles really hight when you first start it and then comes down to about 1500 then eventually comes down around 1000 but i can still hear the miss with the rough idle. I'm really starting to get pissed off now because I hate driving it like this to work. Guess i'm going to start checking injector and Ignition system now. I didn't read the codes yet now since I put the new parts on but the CE light came on almost instantly. I appreciate all the answers and tips guys. Please keep them coming.

 

[XLTsplash]

Did the high idle and misfire start at the same time ? Did you replace the plugs and wires before or after the misfire started ? When you unplug the IAC does the RPM drop ?