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V6 (1994-2004) Mustangs Technical discussions on the 3.8L and 3.9L V6 torque monsters
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Old 07-27-2011, 03:40 PM   #1
Chucks95RT

 
Join Date: Jul 2011
Vehicle: 1995 Ford Mustang
Location: Pennsylvania
Posts: 37
Default High Idle and Surging Issue 3.8 V6

After reading through literally hundreds of threads (I support seaches, they are valuable) I am still a bit baffled. This will be a little long, but I felt step by step is the best info to give you guys. I just purchased the car, and have no real solid history on it. It has a new TPS and coilpack that I can see.

1995 3.8 auto

AC blowing only through defroster - Found the vacuum line tree on the drivers side firewall and line was broken - Replaced with new line, AC fixed...blows from each position as the selector tells it to. TY all for the posts that gave me the info to fix it.

the problem at hand...
High Idle and Surging in gear - without touching pedal, I can get to 55mph. Riding the brake in traffic is getting old...i'm going to need new rotors soon.

Checked the intake from filter to the TB.
Purchased electrical contact cleaner(ECC) and TB cleaner from AZ.
Checked filter, new and clean.
Cleaned Mass Air Flow Sensor with ECC in the housing.
Cleaned Air Temperature Sensor with ECC while in tube.
Removed intake tube and Air Idle Control valve from TB.
Cleaned AIC with electrical cleaner, wasn't sure which to use...played safe. Reinstalled AIC, reused good gasket.
Started engine...idled kinda nice with intake tube off.
Sprayed TB cleaner intermittantly into TB while manuallly moving butterfly.
Shut down engine.
Reinstalled tubes and double checked all connections.
Started engine and cried. Idle is consistantly at 2000 rpm

With MAF unplugged, the idle is rough around 800, with it plugged in...2000 constantly.
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Old 07-27-2011, 04:30 PM   #2
Daehawk
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Im not sure its in all the stuff posted because Im not a mechanic but cant you just turn down the idle?
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Old 07-27-2011, 10:03 PM   #3
Chucks95RT

 
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Vehicle: 1995 Ford Mustang
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Good question...I'll explain best I can

Adjusting the idle is a mechanically adjustment. The throttle has a spring that tries to close the throttle completly, resulting in idle of zero. A "set screw" opposes the spring and adjusts the idle high enough to maintain a smooth idle. This adjustment can be changed pretty easily with a screwdriver.

This issue is with the IAC(Idle Air Control) over-riding the mechanical setting by opening/closing the TB "automatically" with vacuum. This IAC gets readings of air temp and volume from sensors and adjusts the idle speed to maintain the mechanical setting's idle speed. More/less air, hot/cold air make the engine run different, the IAC adjusts to get the "perfect idle"
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Old 07-27-2011, 11:37 PM   #4
Daehawk
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AH. Then my guess would normally be a bad sensor but that usually triggers a fault code and CEL.
__________________
--------------------------------------------------

2001 Satin Silver Mustang V6
BBK Power Plus 70mm throttle body
Mac cold air intake
MAC long tube headers
MAC off-road H-pipe
MAC true dual exhaust
American Racing 5 spoke
Nexen N3000 255/40ZR17 tires
MAC white face gauges
Cobra front end

My exhaust videos:
http://www.youtube.com/watch?v=aSq9Tr5N_W0
http://www.youtube.com/watch?v=3GMoohiXdaQ


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Old 07-29-2011, 02:14 PM   #5
Chucks95RT

 
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Also correct...the CEL will come on when the parameters from the sensors are outside "normal operating range". Running like it's 12 degrees is within parameter...but screws the idle when it's actually 95 degrees.

I'm hooking up an AMP and sub tomorrow, I'll dc the battery for a while and see what happens. I'm also doing the IAC modification with a piece of aluminum and 2 gaskets...that should force my idle down.
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Old 07-30-2011, 12:39 AM   #6
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Good luck with your 95 stang, hopefully it doesn't fall apart like mine is lol
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Old 07-30-2011, 11:21 AM   #7
Chucks95RT

 
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Well...if you were left outside for 16 years...you might be fallin apart too. I had low expectations with this car, so I'm not real upset about any of my issues. I always wanted this body style in a convertable.

I graduated HS in 92......bought a 91 Trans Am new and ran it for years. 1998 Ranger XLT/2001 Ranger EDGE/2004 SVT Focus/2005 Ranger EDGE/2007 Focus ST...took til now to get get my stang Should have bought the Mustang between the TA and the Ranger, but didn't.
I've had too many cars.
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Old 07-30-2011, 11:21 AM
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