1987 Mustang Idle & Low RPM Trouble - MustangForums.com


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Old 10-04-2005, 01:35 PM   #1
Mustangs_Are_Forever
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Default 1987 Mustang Idle & Low RPM Trouble

Okay....me and dad are exhausted.....so I'm going to the pros.


The car is a 1987 Ford Mustang. Bone Stock, like it came from the factory. At idle it surges from about 800 rpm (almost dies out, but not quite) to 1500. While riding at low RPMs, it chuggs, after you get up to speed, it runs fine. It is using WAAAAAAY too much fuel. We put it on a diagnostic check from a friend, and it says that the EGR valve and the o2 sensor number 2 is the problem. It says the car is putting out DOUBLE as much gas as it is supposed to. So dad and I have replaced the following.


Both o2 sensors. Did nothing to help the problem.

Both the EGR valve and sensor. Did nothing to help the problem.

Have also replaced the Throttle positioning sensor. Did nothing to help the problem.



Anyone have ANY ideas? Our newest thought was that it may be the Fuel Pressure Regulator, but we aren't 100%. Any input would and will be appreciated.
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Old 10-04-2005, 02:45 PM   #2
grabbem88
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Default RE: 1987 Mustang Idle & Low RPM Trouble

that should of fixed it..maybe?....did you by chance recheck for codes??....did you clear the computer???just unhook the cables and let sit for 30 min....
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Old 10-04-2005, 02:48 PM   #3
88BlueGT
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Default RE: 1987 Mustang Idle & Low RPM Trouble

I have the same problem but Im almost positive that mine are due to vaccume lines. Are all of your vac lines hooked up correctly?
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Old 10-04-2005, 02:55 PM   #4
grabbem88
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Default RE: 1987 Mustang Idle & Low RPM Trouble

could have a plugged or bad vac. line/tree by the egr valve???
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ORIGINAL: 88BlueGT

I have the same problem but Im almost positive that mine are due to vaccume lines. Are all of your vac lines hooked up correctly?
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Old 10-04-2005, 04:36 PM   #5
Mustangs_Are_Forever
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Default RE: 1987 Mustang Idle & Low RPM Trouble

Well I do know of 1 vaccum line that is disconnected, but it has been disconnected for a looooong time, possibly 3 to 4 years, so I son't think that that is the problem.


And as for the diagnostic check, we ran it twice. once with car turned off, and once while the car was on. Will disconnecting for 30 minutes change anything?


And does anyone here even think it is the Fuel pressure regulator, or if it is worth it for us to try and replace?
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Old 10-04-2005, 09:07 PM   #6
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Default RE: 1987 Mustang Idle & Low RPM Trouble

Another friend mentioned it could be the engine coil, what do you guys think of that solution? Yeah or nay?
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Old 10-04-2005, 09:57 PM   #7
Scooterman
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Default RE: 1987 Mustang Idle & Low RPM Trouble

have same model car and everything, had same problem, turned out mine was the vacuum lines, and a bad Idle control valve gasket, so i ended up replaceing the whole valve, now it idles perfect, look into that stuff, b/c i spent weeks with this problem, and so many solutions, turned out to be those 2 things.. i no whats its like to have idle problems
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Old 10-05-2005, 10:43 AM   #8
Mustangs_Are_Forever
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Default RE: 1987 Mustang Idle & Low RPM Trouble


Quote:
ORIGINAL: Scooterman

have same model car and everything, had same problem, turned out mine was the vacuum lines, and a bad Idle control valve gasket, so i ended up replaceing the whole valve, now it idles perfect, look into that stuff, b/c i spent weeks with this problem, and so many solutions, turned out to be those 2 things.. i no whats its like to have idle problems
Well here is the weird part, about 6 months ago, we DID reconnect that 1 vaccum line that we could see was un-done. The whole car started to run like s**t with a capital S. So then we disconnected, and it ran fine. I swear, if I didn't know any better, I'd say the car was alive.


And also, why would the computer tell us it was using twice the amount of gas it was supposed to use, if the problem was the vaccum lines? Would the vaccum lines make it run like that? The twice as much gas thing is what led us to believe it was a fuel/exhaust problem....
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Old 10-12-2005, 05:17 PM   #9
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Default RE: 1987 Mustang Idle & Low RPM Trouble

Update: Did the engine coil. Nothing changed. However, when we replaced the EGR valve, sensor, and H2o sensor, we were not aware you had to reset the computer to get them to take effect, so, looks like we'll have to reset the computer soon, and see what we get. If it doesn't work, then all I can say is, vaccum lines here we come.
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Old 10-12-2005, 09:05 PM   #10
93notchbac
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Default RE: 1987 Mustang Idle & Low RPM Trouble

The best way to reset the computer is unhook the bat leave unhooked for 5 min, hook it back up let the car idle for 2 min with no acc on then turn on ac let idle for 2 more min then your ready to go. That process is what ford recemends.
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1987, 50, ac, car, idile, idle, low, lx, mustang, o2, problem, problems, sensors, surges, turn, vacuum

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