I just got a rebuilt 4.2 in my F-150. It is mostly working, but at idle and when putting it into gear, starting from a stop, etc. it hesitates and runs rough. Sounds like it is going to stall. Once I get moving it sounds fine. Just had a shop run through anything they could think of and had it hooked up to a code scanner.

It shows intermittent missing, all o2 sensors are giving readings withing the right range. They are suggesting possibly EGR valve or cam sensor. If it is cam sensor, wouldn't it run rough at all speeds? Would a bad EGR produce these symptoms?

In any case, they cleared the computer and told me to drive for a couple days and see what comes up. They also complained about the 97 computer not being descriptive enough.

Any Ideas?

 

My EGR tube came lose, and caused me to drive like I was misfiring all together, but disappeared once I was going. Definately look into the EGR.

Garrett

 

I think that removing the EGR vacuum tube makes no difference in the performance. May be an indication that it isn't working you think?

 

isn't the egr valve that round metal flying saucer looking thing? My trucks been running funny as well lately. I changed the coil pack and plug wires, which seemed to help quite a bit, but it still seems like it's missing under heavy loads or when I punch it. I also get some crackling noise coming from my motor. Not sure what that is. I've heard people having noisy clanky cats, it's possible that that's all the noise is.

It all started when my 3 of my Taylor HP wires (junk) popped off my coil pack when driving and was arcing all over the place. Cracked my coil pack. I replaced the coil pack and popped on all new motorcraft wires. But I think that there is still something else that got messed up in the process.

 

Broken Sockets,
Is it a new EGR valve? I wonder if the hoses were re-connected properly? It sounds to me like you are on the right track. EGR that is.

 

Your Exhaust Gas Recirculation System should not make any big or suddenly noticeable difference in performance. It is strictly there so that the exhaust can be recirculated into the intake to reduce emissions. The EGR sensor or DPFE Sensor as Ford calls it (Differential Pressure Feedback EGR Sensor) measures the pressure on both sides of the exhaust to make sure it is equal. If it isn't, that means the EGR Valve is not working properly. The EGR Valve is the round UFO looking thing right in front of the block behind the coolant and A/C hoses. When I replaced my EGR Valve and DPFE Sensor, I was told to run the truck with them off for a minute or two. It ran fine, even during high revs to get all the carbon out.

There are several tubes and hoses associated with the EGR System. Which one did you notice come loose when you had the rough ideling problems? Maybe it was for something else.

 

Under the throttle body is a rubber 90* boot,which is connected to a plastic tube which runs to the PCV valve on the rear of the passenger side valve cover.Check these connections for any leaks.They are known to get holes in them,which in turn makes the engine run rough and hesitate.If you are getting any EGR codes ide look at replacing the DPFE sensor.These are known to get excess moisture in them,corrode and go bad. Good luck and keep us posted!

 

Man, all these big words make my head spin in the morning...

 

LOL... I was wired last night when I wrote that. I hear your truck is doing better...is that right?

 

I haven't gave it a full throttle top speed test on the highway yet, so I'm still not 100% sure I've solved everything. But it feels good around town. Lesson learned??? Not all aftermarket parts are better than OEM. Stick with motorcraft for plugs and wires, there are none better.

Tom

 

Yeah, I saw your posts. You know, in addition to meeting some friends and talking about a common interest, you really can learn a lot here. Are there ever any "Get-Togethers" for the 4.2 guys and gals? I see a posts in the events section, but never any for 4.2's or anywhere close to me. What do you think?

 

Well you just missed one in TX. A bunch of us (I couldn't make it) all met in TX not too long ago. You gotta hook up with Joe and jimmy and Strick. Post a new thread if you want to see if you can organize something.

 

Sorry Tom, but I CAN"T resist.....

From a post of yours:
" Again, motorcraft wires, expensive and hard to get for me. I upgraded to Taylor SpiroPro wires. They are far superior and only 79.00 for a set."

I am a believer in the OEM wires and plugs. I know others have differing opinions, but for me, they are the ticket.

Again, sorry friend...I just couldn't help it....

 

Very funny Mister.

However, I'm one who will always admit when I'm wrong. Hence the "lesson learned" comment. Not to mention I've posted several comments about my wrongness in the Taylor wire's. I'm confident enough in my masculinity to be able to admit when I'm wrong. I've also commented many times regarding mistakes sometimes being the best form of education.

So have your fun mister moderator and enjoy your laughter on my behalf, because, well because I'm fun to pick on....I'm very "pickable", you cute man you....

Tom

 

Oh and by the way, I've found a website (fordpartscheap.com) that has them for 76.95 a set. That's even cheaper than the Taylors and 8mm as well.

Tom