Running like %$#%#%#

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My 1990 Aerostar (the type with the larger engine) was running great, Nice and smooth, good MPG, peppy as they get. Has been well maintained.
Then it needed an new alternator. Still ran fine other than the things that a dead alternators cause.
I had the alternator replaced. It has run like %$#%# since then. The check engine light comes on after 5 miles. The engine sounds OK for maybe 2 seconds and then makes sort of a lunging sound, like it is revving up and letting off. Over and over. It sounds like a engine would if a person was pressing and letting up on the gas pedal. It hesitates when I take off from a stop. It is more likely to die if I take off fast.
The car repair guy has spent hours trying to figure it out. He and his guys ran diagnostics. Found nothing other than an oxygen sensor. Had that replaced. He sounds quite frustrated. I think he has done his best. Don't think he want to ever see the thing again. Last we spoke, he suggested that I take it over to a Ford dealership to see what they can figure out. Am hesitant about that because of previous experiences with dealerships.
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Other info:
I went over a big bump.
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1990 Aerostar opined in

DIdnt you just post this Saturday?
HAve you tried charging the battery, disconnecting the Alt wires and seeing if it still happens as the other replies suggested?
You can do this easily once the engine has warmed up and it should be evident, then, if it's a bad alternator.
What are the code(s)?
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| | > x-no-archive: yes | > | > My 1990 Aerostar (the type with the larger engine) was running great, | > Nice and smooth, good MPG, peppy as they get. Has been well maintained. | > Then it needed an new alternator. Still ran fine other than the things | > that a dead alternators cause. | > | | | > | | DIdnt you just post this Saturday? | | HAve you tried charging the battery, disconnecting the Alt wires and seeing | if it still happens as the other replies suggested? | | You can do this easily once the engine has warmed up and it should be | evident, then, if it's a bad alternator. | | | What are the code(s)? |
Sorry, neither my post or any reply showed up in my newsreader. I double checked before reposting. Please repost what you wrote before, or send to the email addy. The mechanic claims it has nothing to do with the alternator.
Battery shows as fully charged. The rig starts right up. It is just running rough. It sounds somewhat smoother until the Check Engine light comes on. All of this started After I had a new alternator installed. I don't know that it is at all related.
Thanks for any suggestions you may have.
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1990 Aerostar wrote:

What are the codes? That's the first thing you check if the check engine light is on. You do not need a code reader to extract the codes from that vehicle. An analog voltmeter or a 12V test lamp hooked up to the diagnostic connector will show you the codes as the meter needle moving or the test light flashing.
http://www.dalidesign.com/hbook/eectest.html
I suspect it may have something to do with the mass air flow sensor, maybe the mechanic broke a MAF sensor wire when he was pulling off the intake tube from the air filter to the throttle body.
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