This is a picture of the EGR ports in the throttle body elbow of a '98 4.6L. Those two circled areas should be open passages that allow exhaust from the EGR valve to make its way into the intake air stream. Instead, they are completely clogged by carbon or oil or a combination of the two.

I am not sure how many miles were on this engine, but I'm guessing it had quite a few to build up that much deposit.

https://www.f150online.com/galleries...7335&anum=2314

 

That will by the way turn on a ses light.

 

Wow, now that's a carbon problem if I ever saw one. I'm get home from the road in January, and I'm giving mine a going over. That's a real eye opener! Thanks Ted'98!,,,98

Just thought I'd save people from opening another window. This pic really hits home about the importance of a clean EGR system!

 

I know what you mean there and that build up does cause some pinging but it's not the only cause of pinging. Last winter mine would ping only when the temps dropped below 55* while above 3000 RPM on 87 octane, 89 would help, 93 would cure it. This spring I got several CEL indicating problems in the EGR system. Upon removal of the TB I found those two 5/16 ports had about 1/4 inch of growth out of them and just a pin hole to breathe through. I also replaced the EGR valve (just for the heck of it) and replaceda bad DPFE sensor. Figured it was all solved this year, WRONG. It now seems to lightly ping when temp is below 55* and light throttle around 1500RPM, then ping pretty hard above about 4000RPM.

I did all kinds of things this summer to help the truck out.
I put in new Motorcraft Plugs, cleaned MASS, cleaned TB, clean K&N. It still pings on 87 below 55*, 89 almost cures it. I'm pretty sure it is PCM related (aggressive tuning, no chip). A few other sensor could cause this but not sure which and not going to spend hundreds to replace good sensors.

 

Those look nasty. So what's the best way to clean these ports out?

Thanks
Paul

 

Did any of you guys experience a studder between 30-40 mph at about 1500rpm? I have the same pinging but I also have this annoying studder. It is ten time worse when I pull my boat. I have tried almost everything that KYFordFreak has tried and I still have the same problem as well as a CK eng lite code 401(egr low flow). My ports were clogged up as bad as the picture shows and I thought for sure that this would be the cure. Nope!
I have a flowmaster exhaust and a K&N filter sys. Could any of this be related to the problem?

 

I've got the same thing from time to time, 9 times out of 10 it's the torque convertor. A full recirculatory flush and fill for the transmission usually helps it.,,,,98

 

lookintahook
Bear with me this is a little long and I'm a talker.
What all exactly have you tried and what engine do you have? Usually cleaning the EGR ports will solve the 401 problem, if not test the DPFE (differential pressure feedback sensor) and EVR (Electronic vacuum regulator) and/or replace. I cleaned mine and still got code 401 till I replaced the DPFE due to the DPFE not telling the PCM to use the EVR to fully open the EGR. I can give you test procedures if needed.
Surging from a EGR system problem usually happens with excessive flow? Other parts that affect the EGR system are coolant temp sensor, TPS, MASS, and TCC system. Not sure if any of them would set a code 401, but could maybe cause a surge reation.

The stumbling/surge problem at 30-40 I have had too (mine was like 25-45). Mine would happen when crusing along and going up a slight incline or accelerating lightly. That can be caused by several things. To make a long story short, it was my plugs and they never even set a misfire code at all. I thought it was my tranny going shot for a long time. I even had it flushed and shudder fix added to no avail ( at that point I was afraid it required major repair). Other things that could cause a surge type symptom would be a fuel filter, or a fualty fuel pump, partially clogged injector.

That's about all I can think of. Please feel free to correct me where wrong.

 

pheeww. When i read the post where the guy was talking about the surge while cruising at that speed i thought it was a tranny problem with these trucks.
I still haven't changed my plugs/wires/coils/fuel filter. My truck does the same thing at low rpm's going up a slight incline. I thought my tranny was starting to give me problems. So it looks like im going to have to get a portable heater for the garage, cause its cold outside.

 

KYFordFreak,
Thanks for all the info. You definately have some knowledge about this problem. I have a '98 f-150 offroad 4.6L. It has flowmaster exhaust and K&N filter (only upgrades).
I changed plugs and wires when the problem first started. I then had the code read and found out it was 401(EGR Low flow). I then checked for any vaccume leaks (none). I have changed: EGR valve, DPFE sensor, EVR. I was able to take back the EGR valve and DPFE sensor and now that I write this to you, I remember that I then cleaned out the Ports at the throttle body. Could it be possible the the DPFE was also bad and I didnt know it because the ports were also clogged? It just seems that I would see some difference by changing all this stuff if the EGR sys was causing the studder. I am now wondering if I have a different problem causing it and the EGR code is just coming up first. What do you guys think, other than the obvious that I cant fix it.

 

I ran a K&N in my 98 and it gradually started pinging. I've gone back to a paper filter and cleaned the MAF (was fouled - sooty from K&N) and it's running like new again on 87 octane.

 

hey thanks for the post this is really gona hlep with my 98 4.6 thats pinging. Thing is, i havnt spend much time under my hood and im not real sure how to do this procedure. If someone has step by step pics that would really hlep. ALso what do you use to clean the clogged ports?

 

lookintahook
What you described about maybe the ports being clogged AND having a bad DPFE is exactly what happened with my truck. I bought the DPFE and was going to put it on but a Ford tech on here (jefflaws) told me to clean the ports first. I did as he said and it didn't fix it, tested DPFE and got 2.8v but wasn't for sure if I tested it right. I was fed up with the studdering problem and took it to a Ford dealer to run a full diagnostic (my scan tool is a cheapie...POS). That's when they said I had a problem with my secondary ignition (plugs and wires). Wires were almost new so just changed plugs and problem was fixed. I asked if they could check on the EGR code as well and I was told it would be another diagnostic fee. When I went to leave with my repair order it stated DPFE sensor voltage out of range (2.8v), needs repair before fully diagnosing the ignition problem. So I got real lucky and got ideas on how to fix both.

If you want to fix this thing yourself, I suggest you buy a digital voltmeter if you do not have one. They are easy to use and a good investment. Along with a repair manual you can test that DPFE and almost every other thing on that truck.
I know you just did the plugs and wires but maybe there is something that is missed here. Do a quick look at night with no light around and see if they are arcing. You can also check each wire with your meter. They should have no more than 8000 ohms per foot. I assume you used lots of dielectric grease as well. The fuel filter is not a bad idea either.

If your stubborn and cheap like me, you can find most problems, except the pinging. I might have to try switching pack to the paper filter trick.

green 98
Sorry bud, no photos here. I was to busy and greasy to take pics at the time. It's not all that hard. Follow what's here and what you find in search. I was nervous when I did mine the first tiime. I now plan to do it again this spring just to check it out and reclean. It provided a nice refresh to power and response when I did it.

 

KYFordFreak,
Thanks for the detailed reply, its nice to know that there are a few of us left who care to share their knowledge with eachother. I will try the DPFE again and retrace my steps and try to figure this out. I do have a manual and have been an Aircraft electronics mechanic in the Air Force for 17 years so I have a bit of meter knowledge... I will give you a holler when I finally fix this thing.. Thanks again!

 

lookintahook - I salvaged my DPFE sensor by cleaning it out with WD-40. I unbolted the sensor from the engine, turned it upside down so the two tubes were pointed upright, then filled them up with WD-40 and let it sit for a while.

I turned the sensor over to drain out the fluid and it was black! I let it air dry for a while and hooked it back up and it was functioning properly again.

I have one of the metal sensors, I've read in a couple of places that the black plastic DPFE sensors go bad very quickly.