Rough Idling 93 Aerostar
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Joined: Jun 2003
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From: Anchorage AK
Rough Idling 93 Aerostar
Hi all, Just found this forum.
I have a 93 AWD 4.0 EB. It has 200,000 miles on it. Only owner and I've done all the regular maintenance myself. Up until last week it ran like a champ.
Now, when in park running at idle or when in drive at a stop light, it begins running rough and vibrating a lot.
I have checked all the plugs looking for lack of spark (its almost like its running down 2 cylinders). All plugs look fine and are sparking fine.
After reading all of the threads here I am thinking that it could be the oxygen sensor, egr valve, or MAF sensor. Any ideas on figuring out which one to replace first other than going for the cheapest one?
I have not had the CEL come one during any of this. I'm going to borrow a test set from a friend and check for codes anyhow.
During my last full tuneup(about 10,000 miles ago) I replaced the plugs and wires, PCV valve, filters(except gas).
The only thing I changed since this problem started is the fuel filter.
Thanks in advance
I have a 93 AWD 4.0 EB. It has 200,000 miles on it. Only owner and I've done all the regular maintenance myself. Up until last week it ran like a champ.
Now, when in park running at idle or when in drive at a stop light, it begins running rough and vibrating a lot.
I have checked all the plugs looking for lack of spark (its almost like its running down 2 cylinders). All plugs look fine and are sparking fine.
After reading all of the threads here I am thinking that it could be the oxygen sensor, egr valve, or MAF sensor. Any ideas on figuring out which one to replace first other than going for the cheapest one?
I have not had the CEL come one during any of this. I'm going to borrow a test set from a friend and check for codes anyhow.
During my last full tuneup(about 10,000 miles ago) I replaced the plugs and wires, PCV valve, filters(except gas).
The only thing I changed since this problem started is the fuel filter.
Thanks in advance
Freshman User
Joined: Jun 2003
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Rough Idling 93 Aerostar
I am not an expert or even close to one, but your problem sounds like what I was going through. I have a 91 4.0L. It ran good until I came to a stop or it was in park. I thought it was going to die in traffic if I had to stop, no CEL either. I replaced both the MAF and the O2 sensor, nothing dramatic changed. A friend who works with fords saw it and checked it with the diagnostic machine and everything checked out okay. So while it was running, he reached in the engine on the back side of the engine and touched something and it smoothed right out. He said I had a vacuum hose that wasn't attached, once that was hooked up, runs smooth! Hope it is that easy for you!
Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
Rough Idling 93 Aerostar
Yes, TPS = Throttle Position Sensor, I would check it if there are no obvious vacuum leaks like cracked hoses, broken lines loose fittings etc.
I Even had a blend door modulator in a heater/- A/C plenum chamber develop a leak & cause rough idle condition. I'd turn the A/C to outside air & the engine would pick up & straighten out. Put climate control on Max Air, (recirculating interior atmosphere) and there was the rough idle. . .that was a tough one to diagnose!
There's also an IMS or idle motor switch which kicks up the idle speed for when A/C compressor kicks in, or wheel is turned, or a load/demand happens for the alternator etc. It doesn't really cause a "rough idle" per se' but can cause low idle speed & intermittent stumble which can seem like a rough idle.....
I Even had a blend door modulator in a heater/- A/C plenum chamber develop a leak & cause rough idle condition. I'd turn the A/C to outside air & the engine would pick up & straighten out. Put climate control on Max Air, (recirculating interior atmosphere) and there was the rough idle. . .that was a tough one to diagnose!
There's also an IMS or idle motor switch which kicks up the idle speed for when A/C compressor kicks in, or wheel is turned, or a load/demand happens for the alternator etc. It doesn't really cause a "rough idle" per se' but can cause low idle speed & intermittent stumble which can seem like a rough idle.....
Posting Guru
Joined: Jul 2003
Posts: 2,222
Likes: 1
From: East Central Florida
Rough Idling 93 Aerostar
See if moving the throttle a litle bit causes a change. I don't mean opening it, I mean applying slight pressure to it with your thumb & fore finger. If it makes a difference. shut the engine down & test the TPS for current value.
Calibrate a VOM to the right scale according to the test manual & hook the meter to the semsor for a readout. NAxt with the VOM connected & turned on put the TPS into several positions like closed, slightly off idle, partial throttle, half throtle, WOT and so forth. Check the readings for variations. What's important is the readings At closed/idle and at WOT. If they are within parameters specified for your system according to VIN, then the TPS is good & the problem lies elsewhere. . . . . FBp
Calibrate a VOM to the right scale according to the test manual & hook the meter to the semsor for a readout. NAxt with the VOM connected & turned on put the TPS into several positions like closed, slightly off idle, partial throttle, half throtle, WOT and so forth. Check the readings for variations. What's important is the readings At closed/idle and at WOT. If they are within parameters specified for your system according to VIN, then the TPS is good & the problem lies elsewhere. . . . . FBp
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New User
Joined: Jun 2003
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From: Anchorage AK
Rough Idling 93 Aerostar
Went looking for disconnected or broken vacuum line an low and behold when I pulled the engined cover inside, I found a lined that comes from the passenger side of the engine and runs to the drivers side... It was disconnected. It took me awhile to find where it came loose from but fortunetly I found it.... All is well once again.....Thanks
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Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
Rough Idling 93 Aerostar
Jdagg98
Great !
The most critical thing about all late model "New Tech" engines is ro remember BASICS 1st!
I've seen guys spend hours chasing ghosts in their system which were the result of something as basic as your vacuum line leak, or a bad electrical ancillary ground point or stuff like that.
If you are familiar with "Occams' Razor" it certainly applies here.
Sir William of Occam stated it in the early mid 1400's and it still applies today as it did then. FBp
Great !
The most critical thing about all late model "New Tech" engines is ro remember BASICS 1st!
I've seen guys spend hours chasing ghosts in their system which were the result of something as basic as your vacuum line leak, or a bad electrical ancillary ground point or stuff like that.
If you are familiar with "Occams' Razor" it certainly applies here.
Sir William of Occam stated it in the early mid 1400's and it still applies today as it did then. FBp
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