Rough Idle
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We are happy you have chosen the best source for Fords!
Enjoy FTE....and
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Posting Guru
Joined: Jul 2004
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From: Mitchell, SD
Welcome! 
I would try cleaning your IAB. If that does not work, replace, common Ford issue. Also it is probably overdue for a decaboning. (do a search for seafoam.)
Also how old are your plugs and wires?
I would try cleaning your IAB. If that does not work, replace, common Ford issue. Also it is probably overdue for a decaboning. (do a search for seafoam.)
Also how old are your plugs and wires?
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Plugs and wires should be replaced at least every 25-30k miles, unless you have double life type plugs (60K), but the wires should still be replaced often. You will notice that under most circumstances, the plugs will outlast the wires.
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Joined: Apr 2001
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I would agree with most of the aforementioned suggestions. I would also add a possible vacuum line problem to the list - especially if the problem suddenly started. Remove the rear engine cover from within the passenger compartment and check the vacuum "tree" near the top, left, rear side of the engine. There should be 4 or 5 vacuum hoses of various sizes attached to the "tree". There will also be 1 or 2 unused ports but these should have a small cap in place. Engine back pressure sometimes dislodges the lines or caps. A quick, inexpensive fix if this is the case.
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
I agree with the vacuum line theory too. Check all the vacuum hoses, and make sure they are still flexible. I had forgotten, but recently, I had to replace the vacuum lines in our Aerostar, and rough idle was one of the symptoms.
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Freshman User
Joined: Aug 2004
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Will a hole or two in the muffler cause rough idleing? My 94 has skipped for a while now but I figured it was a back pressure problem due to the holes. I was going to replace the muffler this weekend to see if that would help. From reading a few post this morning it appears I might have other issues as well. I might need to suck-it-up and go get an engine analyzer performed.
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From: Wichita
Originally Posted by WARedBear
Will a hole or two in the muffler cause rough idleing?
Go with the tips already suggested. It could also be an injector. Read the plugs when you change them.
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Yeah, if its running rough, there is a pretty good chance there is at least one code. Do a cylinder balance test too (If you have an OBD-I eg EEC-IV). That can find any missfire/injector issues. What that does, is the computer shuts off injectors one at a time, and measures the difference in performance. If it does not degrade by the expected amount, it means that that cylinder was already haveing problems.
Freshman User
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Let me clarify the running rough. I called around yesterday and stopped by a garage and the one thing they all asked was if my "check engine" light was on. NO it is not. Strange! The van runs smooth at 55-60 mph but skips real bad at 70 and also if I accelerate up a hill. I've had problems with vacuum lines blowing off of the vacuum tree and I don't know if I reattached them all. I need to find the vacuum diagram and see if I can verify that they are all connected. I found a shop that will hook the van up to an analyser for $40 so I am going to try and get it in there. Thanks for all of your comments. Please keep them coming. I need to get this fixed because it is sucking gas like crazy. Which makes me wonder if I'm getting too much gas. I say that because I can floor it, the van downshifts, and runs okay. Just another thought.......
Former ******
Joined: Nov 2004
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From: Salt Lake City, Utah
Vacuum lines should never blow off. Replace the PVC valve if they do. Also, replace the vacuum lines, and if nessecary, clamp them on. Also, if they blow off, check the transmission modulator.
The van will not get too much gas unless there is another issue that like a faulty O2 sensor, or a faulty MAF sensor. Also, check for fouled plugs. I'm thinking you have a vacuum leak, and thjat is the cause of the rough running.
Your vehicle is an OBD-I, so go to your local auto parts store and get a code reader for OBD-I fords. Should run about $30, which is a lot cheaper than paying a mechanic to read them for you. Follow the directions and see what the computer can tell you.
The van will not get too much gas unless there is another issue that like a faulty O2 sensor, or a faulty MAF sensor. Also, check for fouled plugs. I'm thinking you have a vacuum leak, and thjat is the cause of the rough running.
Your vehicle is an OBD-I, so go to your local auto parts store and get a code reader for OBD-I fords. Should run about $30, which is a lot cheaper than paying a mechanic to read them for you. Follow the directions and see what the computer can tell you.