Before I start, I did search the forums for this topic but if I missed it, please be gentle

I have the 4.6 in SC 4x4 and it has been great 82,000 miles of trouble free running. In the last few months it has started surging about 150 rpm.

Symptoms:
It's very noticeable when I first start it up. It will surge in park slightly. When I run it slow, it surges enough that you can hear and feel it. It stops in less than a mile though and is much less noticeable after that. It doesn't surge at all when you floor it. The gas mileage has not been as good either -1.5-2 mpg.

What I've done so far:
I've changed the spark plugs, air filter, cleaned the MAF and the throttle body. I don't think it's electrical because it isn't affected by steep grades, pulling a load or acceleration. It hasn't thrown a code yet either.

I'm baffled. I hope you can give me some ideas.

Thanks

 

Clean the throttlebody and mass air sensor

 

I can definately do that again. I took the throttlebody completely off (it had some gunk) and cleaned it, the MAF was taken apart as well. Though I didn't see anything on it.

I wish the darn thing would throw a code!!

 

Would a clogged catalytic converter throw a code?

 

Possibly - if it detects low efficiency.

I'd throw a bottle of Techron in the gas to clean the injectors.

 

Have u donev the plugs and cops yet?

 

Yes to the plugs. No to the COPs. Maybe it's my old way of thinking, but I assumed that if the problem were ignition, it would be worse under load. I haven't had problems going up grades or pulling. It may be worth looking into though.

Thanks

 

To check for misfire, accelerate gently so it shifts into OD and the converter locks by 40-45 mph. Cruise at this speed momentarily, then accelerate SLIGHTLY - not hard enough to unlock the converter or downshift. If it's gonna miss, it will under these exact conditions.

 

I'll try it. at this point im thinking its got to be related to the throttle body.

 

I'm getting frustrated with this problem and at this point I'm throwing parts at the problem and it's getting expensive. Since the last post, I took it to the ford dealership and they said they couldn't be sure but though it was the TB, I replaced the throttle body. Not the problem, I've now replaced all the COPs. I thought the problem was fixed but this last week it got cold here temps in the 20's, I ran it right after changing the COPs and it ran well, now that the temps are back up, it's surging again.

Any ideas?

 

I admit I'm baffled. It does sound like a throttle body issue, but that's been addressed.
Have you checked for corrosion damage on the fuel pump driver module? Grasping at straws here, but the temperature warming causing re-occurrence of the problem made me wonder if humidity in the FPDM (if it is corroded through) might be a problem. At least it's free to look at the part.

 

I appreciate the help, I'm in the straw grasping mode right now. If it's not the FPDM, i'm thinking MAF sensor next, then PCV and EGR. I've also given some thought to reflashing the PCM by connecting + and - battery cables.

 

No, don't do that. That won't reflash anything. Disconnect the - cable for 15 minutes and that will clear all adaptive learning. If you feel you need a reflash, you have to go to a dealer.

 

Thanks.

I was driving home today and glanced down to see what I'd been praying for for weeks... a CEL 0401 the EGR I just pray that's the problem.

I'm so glad to have a direction, now I'll research how to proceed. I need to take it slow because my nature would have me jump in and start tearing things apart. Any words of caution before I take it apart and start cleaning everything with TB cleaner? I guess I'll need to go pick up some gaskets?

 

I'm getting frustrated with this.. I replaced the EGR, easy peasy 10 minutes. I pulled the battery leads for 20 minutes. It runs worse now. still surging I've got two things left to replace that i can think of.. MAF and PCV.