JKOGREY

Hello everyone! I am new to the forum as we bought my wife recently an '06 expedition 5.4l eddie bauer.

The problem: I noticed that her SUV has a slight hiccup/jerk when driving around 45-50 mph and at low rpms. It is more common when you are driving on an incline/hill but only happens around 45-50 mph and when the rpms are around 500. I thought it may be the SUV having issues making up its mind to either stay on the gear or go down a gear. If I accelerate and at least over 1k rpms, there are no issues.

I searched the internet and forums and found that the most common solution for this issue are the COPs and plugs. So, I replaced them all myself the other day and luckily none broke off. I figured that running intake cleaner first and then getting the engine at running temperature made the job easier. I was able to do one side and then had to drive the SUV around again to do the passenger side.

Anyways, I got that all done and the vehicle still has a slight hiccup.

**I want to add that I have had the recent P0420 which is a bad catalytic converter**

I went to a shop and they confirmed that it was the CAT but did not pay for the diagnostics to determine which one is bad.

To make this short, would a bad CAT cause my issue? I read where someone said that a plugged CAT would do this. Are they correct?

If not, what else should I do to the SUV? My friend was helping me and he said we should not use anti-seize on these Fords, so I only put anti-seize on 4 of 8 plugs. And I think i forgot to use dielectric grease on two of the plugs. Would these cause the issue?

Any help is greatly appreciated and Happy Thanksgiving...looking forward to the day off, all the food, and football!!!

~James

lariatboy

Clogged cat could definitely be a possibility. When you're in that rpm range, especially under extra load (incline, slow accel), you're torque converter is locked up(OD), and the back pressure from a clogged cat could be causing a slight misfire.
Also check the foam seal around your stock intake filter tray - if it's deteriorated or missing, the intake tends to resonate rather harshly at the speed you mentioned, and can mimic the feel of a misfire or a shudder.

GreatWh1te

My truck just started doing this recently(this week). I was searching the forums to see if someone else posted on it. My air intake box has hardly no foam left on it, might be the issue. Dunno.

Throttlejunkie

iTrader: (1)

^^This^^....Check it. It's cheap and it does cause this problem.

GreatWh1te

I am kinda thinking its the cats over air box. this is a pretty hard miss, there's a couple tiny misses before the one you can really feel. shakes the whole truck when mine does it

azinn10

Try fuel filter cheap and might work

GreatWh1te

had mine replaced around 10k miles ago. I doubt its out. Mine is getting worse though, now doing it from 40-50 in 4th gear, and 65-70 in 4th gear. I can't tell if its a reall----y bad miss, or a tranny issue. I'm baffled.

Yamifanatic

Hdub I can almost guarantee it the ignition coil from cylinder 4, passenger side closest to the firewall, I noticed my truck did the same thing and then all of a sudden one day the CEL came on and the truck would vibrate bad at idle and at low rpms, it threw the code for igniton coil D primary/ secondary, I replaced the ignition, coil and it has been smooth sailing ever since.

Yamifanatic

btw just an fyi examine the wiring going into that coil, it has a tendency toget too close to the ac hot pipe and melt the wiring.

GreatWh1te

Thanks, I'll look that over when I get off work. I haven't seen a CEL yet, and this has been ongoing for the last 2-3 weeks.