Hello All - My poor old aerostar has been slowly getting rougher as it runs.Now with the onset of cold weather it is now much worse.It's having problems running smooth.Symptoms are as follows-when cold,it idles half decently,but with a noticeable "puh-puh-puh" type noise.When the engine is under load it can realy miss quite a bit.Kicking it down a gear makes it respond nicely but sometimes you can feel it surging.After getting back up to speed and OD wants to kick in it will sometimes buck like the fuel is getting cut off/starved.example-this AM temp was -10C (teens F)
and I started it up as usual(lives in a garage)and it ran sort of rough the first while.After hitting the highway,if you leave it in D long enough,it will go into OD fine as long as you have no load on the engine,or don't mess with the gas too much.Some days nothing helps and you shake alot...
Most noticeable when in gear and stopped at stoplight.It sits around 800rpm but really chugs.Does not feel like it wants to stall though.So far I have- checked air filter- semi cruddy-will change)
inspected MAF sensor-looked great cleaned with carb medic anyway.Poured a bottle of injector cleaner in with gas-what the heck.Next is IAC -hopefully will get around to it tonight.
I am hoping its not plugs,last batch have maybe 50 - 70,000km on them.Will check my notes..
Also-no check engine light or other complaints

 

When did you last change the plug wires?

 

Plug wires were changed out with the plugs last time.I did not do it myself so i cannot testify as to what type/quality plugs or wires were used.I get the impression from the 100's of posts that aerostars can eat plugs pretty quick if not the right type.

 

I have heard that it is not uncommon for shops to not do a complete change out on the plugs, especially the rears. My friend that buys and sells these things tells me it is not uncommon to find 4 or 5 'new' plugs and one or two 'old plugs that have huge gaps in them from being so old. He said that replacing all the plugs made a big deal when he would tune them up.

Might be worth a check

 

I'm sorry to say, that in this City (Winnipeg), the only way to make sure they have changed the plugs is to check each one. However, seeing as the plug wires will have to be re-routed to the correct plugs anyway, why not.

 

Regarding the wires,etc..I had a chance to dive under the hood last night to check things out.The wires all seem to be exactly the same and in the same shape.All wires are of the Bosch variety.Did not check any sparkplugs as I was short of time(hockey game on TV)Funny thing is the last time the aerostar needed wires,it would get upset on the damp rainy days and it has not been following this routine.
I did,however,get a chance to pull out the idle air control valve.I have never seen anything that dirty in my life!-black as black can get.The small pintle would still move however along with the mate on the sensor itself.
I spent about 20 minutes cleaning it with carb cleaner,but it is still not perfectly clean.A quick run after assemly seemed to make no difference thoug.
NOW-this morning-temp just around freezing with rain.The thing started up fine and ran beautiful all the way to work(80Km) without any complaints.Even going uphill in OD at 80Km/hr and tach pulling under 2,000.This normally makes for some bucking and complaining.
Very strange...

 

Your symptoms sound like the same symptoms I had with my 3.0L
Ranger, when I found the previous owner had installed Bosch
plugs in it. The bucking (or mis) problem was eliminated by installing Motorcraft plugs!!!

 

Did you find out what was wrong my 97 4.0 does the same thing.

 

Plugs were the problem-changed them out and it runs
like a charm now.