Replace the oil soaked vacuum lines. The oil soaked lines will swell and that may make them easier to pop off. If you have not already replaced the modulator, do so, a quick search of the forum should find several articles on the subject.

What kind of plugs and wires did you buy. Most of us have found that anything other than OEM plugs and wires is a waste of money. You will find yourself replacing them way too often, which is not fun on an Aerostar. I don't know about you, but I do not want to have to replace them sooner than 50,000 miles, some people have had 4 times that amount on the original plugs (not recommended).

 

waredbear,

it's your lucky day...NO distributor to have to tear your hands up replacing cap and rotor....all the 4L Ford OHVs are electronic distributorless ignition systems...

bear river has pointed you on the way....Autolite or MC double platinum plugs and 8mm silicone premium ig. wires....too many reported problems with other brands

also pull clean or replace the IAT sensor...they become oil coated with major ATF intake
and time to clean all that ATF baked on crud off the intake valves, combustion chamber and rings....can of Berryman B12 thru 1/8" tube into TB while engine running at 2k rpm.....let soak for 2 hours and out to the freeway for a hard run

Aero DIYer motto, Do it once and do it right- bleed less
this job is a 1 case Aero beer job under the shade tree

 

I get right at 100K with OEM double platnum Autolites, and I change the Wires every 2nd time using Motorcraft set.

As for backfiring on start up, if it's more of a "sneeze" than a true 'BACKFIRE", try holding the key in start position just a tad longer and don't release it as soon as you think the engine is going to fire.
Instead, wait 10-15 100ths of a second until you know it did start, then release key.

I couldn't agree more with Bear River. Only solution to petro-chemo deformed vacuum lines is replacement with new lines. Anything short of R&R is not a solution, it's a "fix" or a "patch jobs". Don't waist your time rigging failure, either repair your problems or move on. Also be wary of various vacuum operated servo diaphrams that may decay from petro chemical incursion too.

Riding around with perto products contaminating your vacuum system for any amount of time is a bad idea any way you look at it, IMHO.

I would add the opposite of deformation is hardening or britteling caused from engine bay/ compartment heat. Again replacement is the solution for that problem also.

On vinyl based lines, I've been known to splice in new vinyl tubing with the correct OD, by using neoprene hose with right ID to make a union. I search "U-Pull-It" yards & vehicles I am scrapping for extra ends etc to use for just these sort of repairs. I toss them in one of the compartment drawers of my tool chest as I acquire them. Very handy.

FBp

 

You can try my trick to deal with that inevitable backfire (cough or sneeze). Remove two of the plugs on the vacuum tree and replace with a short length of hose looped between the two. Pick two fittings where one is much larger than the other, so that the same hose will fit tightly on one end and loosely on the other, but still seal. The next time the engine backfires, it will blow the loose end off. That way, you don't have to go hunting for the plug that just got blown off to who knows where.

I am now careful in the way I start my car to prevent the backfires, but every once in a while, someone else drives it, and is not aware of this problem.

 

Just got back from my test drive. Somewhere between the front O2 sensor, the gas filter, cleaning the IOC valve and the spark plugs and wires the skipping has ceased. I am sure it was the plugs after seeing them. One of them had the arm almost fired off and another one had the insulation around the inside rod half blown off...please excuse the technical terms. But she ran smooth as silk. First time in months. So look up....you too can have a smooth running Aerostar...with the good advise of these fine fellows here on this forum...luck....time...and money...

Reid

 

here's my latest update - gave up on the maf & map after poking around and realizing two things. There's a vacuum leak somewhere - i was spraying intake cleaner around the IAC area and was getting an rpm increase - pulled IAC and tried everything I could think of to stop the leak, either I wasn't doing it right or the leak is very close to the IAC. Also I noticed that my plug wires are not "clicked" onto the coil pack and that no matter what I tried i could get them to snap. I'm going to try to find a shop to replace the wires with motorcraft and check the plugs (they have less than 10k on them, they should still be good I hope) and to look into the leak I just can't get in there (I'm a big guy) to work on anything behind the hutch. maybe if I pull both seats out so I can lay down I might be able to. I'd buy another aero and keep this one for standby but the prices are going up around here, guess they are getting to be collectables.

 

The vacuum tree that I talked about a few posts back is located behind the IAC. Spraying cleaner could reach them real easy. You can reach them from the front but be careful. Your arm has to rest on a sharp piece of metal (at least on my Aero) in order to reach them. You might be able to get a good light to shine back in the depths and see the lines. I'm putting my bets on that being your problem.

Reid