97 Expedition rough idle - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

mw1957 · 09-05-2012, 10:43

Little history. Been sitting for a long time. Great shape overall. No fluid leaks of any kind. Ran rough. Replaced EGR, IAC valve. Replaced 3 or 4 COP and all plugs. Ran really good after that for about 200 miles. Now it has started to cough and sputter when I come to a stop. IN addition to the sputtering, it does have what I can only refer to as an ol fashion "flat spot" (like when we had carbs) at cruising speed. I can be going 55 and she kinda shudders a little and it acts like she is being fuel starved. I back off the gas a little and then get right back on it and she clears. But it happens again almost right away. Thanks in advance for any help

**Bert** · 09-05-2012, 10:57

I'd replace the fuel filter and see how it does. Also, Autozone will pull codes for free. The light doesn't have to be on.

mw1957 · 09-05-2012, 12:11

Oh, air filter is brand new too. CEL is not on, but it might still be throwing codes? Ok. I'll check that

**R.S.LOGAN** · 09-05-2012, 12:21

Wouldn't do any harm to check timing if still having problems .

**Bert** · 09-05-2012, 13:26

Not air filter, FUEL filter.

**CatSkinner** · 09-05-2012, 14:53

It'd be nice if you had a fuel gage on the fuel rail while driving to see how pressure fluctuates. Might be worth the investment if the filter doesn't cure it.

mw1957 · 09-05-2012, 15:55

sorry. I can read, really. New fuel filter, same issue. But I can hear a hissing sound back behind the EGR near the fire wall. I can hear it loud when it's at idle and when I accelerate it all but disappears.

**R.S.LOGAN** · 09-05-2012, 16:05

Check all hoses / vac pipes .If its drawing air from a leak it will be running lean causing flat spot .

**CatSkinner** · 09-06-2012, 02:56

Common spots over looked for vacuum leaks: the caps on the vacuum manifold and the bushing for the PCV valve. I've seen with the PCV where it seems snug, but still leaks like crazy.

mw1957 · 09-10-2012, 09:21

Turns out it was the boot (L shaped) at the back of the PCV system. Back against the firewall. Had a hole in it the size of a dime. Damn near rotted thru. Rough idle all gone. Still may have a slight shudder/flat spot. Not as bad. Thought I detected it at about 50 mph but it was slight. I'm thinking I still have one bad COP on here somewhere????